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Single-photon avalanche diodes (SPAD) are photodetectors with exceptional characteristics. This paper proposes a new approach to model them in Verilog-A HDL with the help of a powerful tool: TCAD simulation. Besides, to the best of our knowledge, this is first model to incorporate a trap-assisted tunneling mechanism, a cross-section temperature dependence of the traps, and the self-heating effect. Comparison with experimental data establishes the validity of the model. | In this paper, we present an accurate behavioral model for simulating single-photon avalanche diodes (SPADs). The device operation is described using the Verilog-A description language, which is an analog extension of the common digital hardware description language. The derived model is able to emulate the static, the dynamic behavior and the main statistical effects of an SPAD, such as the turn-off probability, the dark-count and the after-pulsing phenomena. Spectre simulations reveal the validity of the approach showing a good matching between the behavior of the proposed model and experimental results reported in the literature. Copyright © 2011 John Wiley & Sons, Ltd. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,600 |
We present a 50 W ytterbium fibre laser with an intra-active-core Bragg grating. To the best of our knowledge, this is the narrowest linewidth (~100 pm) fibre laser operating in this power range. | We report the efficient generation of 100-W single-frequency radiation with diffraction-limited beam quality at the 1064-nm wavelength by use of a master-oscillator fiber power-amplifier system, consisting of a diode-pumped monolithic nonplanar ring laser as the master oscillator and an Yb-doped large-mode-area fiber as the power amplifier. The emission spectrum, the intensity noise behavior, and further power-scaling possibilities to the >200-W level, which are determined by the threshold of stimulated Brillouin scattering in the fiber amplifier, are discussed. | The review of the laser application practices in mining is followed by the discussion of experimental treatment of carbonate rocks by the continuous fiber-optic ytterbium laser radiation at output capability of 600 W. Local disintegration of carbonate rocks is estimated with a view to show the possibility and practicability of the laser-aided means and technologies in mineral mining and processing. | eng_Latn | 7,601 |
A plasma-dielectric waveguide is presented as a possible optical element for enhancing the phase matching condition in high harmonic generation processes. The phase velocity of the pump wave, in a partially ionized plasma, is controlled by its interaction with dielectric walls within the waveguide. The phase velocity is adjusted by changing the thickness and spacing of the dielectric slab walls.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | Harmonic generation is investigated at an intensity range of ${10}^{15}$\char21{}${10}^{18}$ W/${\mathrm{cm}}^{2}$ by using a 280-fsec KrF laser. The highest-order harmonic observed with Ne as a nonlinear medium is the 25th (9.9 nm), which gives the shortest-wavelength coherent radiation ever obtained. The inversions or anomalous peaks of harmonic intensity are first found at the 19\char21{}21st in Ne, the 17\char21{}19th in He, and the 11\char21{}13th in Ar. The intensity dependence of the harmonics is measured over a range of ${10}^{15}$\char21{}${10}^{18}$ W/${\mathrm{cm}}^{2}$. The observed distribution of harmonics is discussed and compared with the previous reports. | We demonstrate the data transmission of 10 Gbit/s on-off keying modulated 1550 nm signal through a long-range dielectric-loaded surface plasmon polariton waveguide structure with negligible signal degradation. In the experiment the bit error rate penalties do not exceed 0.6 dB over the 15 nm wavelength range and received optical power between −7 and 3 dBm. | eng_Latn | 7,602 |
A new approach to design digitally tunable optical fllter system for DWDM (Dense Wavelength Division Multiplexed) optical networks is presented. This digitally tunable optical fllter system uses semiconductor optical ampliflers (SOAs) and DWDM thin fllm fllter based wavelength selection elements. The design is very easy to conflgure, expand and reduce. This digitally tunable optical fllter system is smaller in size, lesser in weight, cheaper in cost, consumes low power and has better timing performance as compared to digitally tunable optical fllter suggested by researchers recently. | We demonstrate a rapidly tunable narrowband wavelength filter using unbalanced Mach-Zehnder interferometers in lithium niobate. It is designed to switch among eight channels spaced 50 GHz apart in optical frequency (approximately 0.4 nm in wavelength) in less than 50 ns. The insertion loss is 19 dB and crosstalk is less than -22 dB. The filter consists of a cascade of three electrooptically tunable unbalanced Mach-Zehnders and a feedback circuit to keep the filter centered on the desired wavelength. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,603 |
We report the synchronization of actively -switched erbium- and ytterbium-doped fiber lasers by means of a single electrostatically actuated deformable metallic micromirror. Synchronized and tunable pulse trains were generated at 1.064 and 1.55 mum with a pulse duration and repetition rate of ~1.5 mus and 32 kHz, respectively. The output dual wavelength beam is then converted in a nonlinear crystal designed for sum frequency generation. Tunable output red radiation close to 630 nm is obtained. | We demonstrate simultaneously efficient generation of cw red, yellow, and green coherent radiations, “traffic signal lights,” by multifrequency conversions from a diode-pumped Nd:YVO4 dual-wavelength laser with a single-pass aperiodically poled LiTaO3. The 1.8 mW red at 671 nm and 0.64 mW green at 532 nm are, respectively, generated by frequency doubling of fundamental waves at 1342 and 1064 nm, and 0.79 mW yellow at 593 nm is produced by sum-frequency mixing of the two fundamental waves, under two fundamental waves of 970 mW at 1342 nm and 940 mW at 1064 nm. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,604 |
Photoreceivers suitable for 100 Gb/s data rates are presented, consisting either of monolithic pin-diodes with travelling-wave amplifiers followed by a copackaged DEMUX, or 90° optical hybrids integrated with balanced detectors forming coherent QPSK photoreceiver OEICs. | An InP based 4×4 Multi-Mode Interferometer 90° hybrid is described. The fabricated device showed a common mode rejection ratio in excess of 20 dB, and less than 1.5 dB variation in responsivity over the C-band. | The oxidative polymorphism of debrisoquine (DBQ) has been determined in 89 patients with colo-rectal cancer and in 556 normal control subjects. Four patients and 34 controls, with a metabolic ratio >12.6, were classified as poor metabolisers of DBQ (n.s.). | eng_Latn | 7,605 |
The spectral width of the continuous wave broadband generated in an erbium doped fiber ring laser containing a dispersion shifted fiber (DSF) in a filterless cavity is found to be governed by the nature of the gain spectrum of the doped fiber, in addition to the nonlinear effects. This dependence is studied experimentally with different lengths of the doped fiber and the DSF. Spectral broadening is demonstrated in the conventional (C) and long wavelength (L) bands using pump powers less than 200 mW, with an appropriate choice of cavity parameters. The generated broadband is demultiplexed in the C-band to prove its utility in optical communication systems. | Continuous-wave (CW) broadband in the C- and L-band wavelength regions is demonstrated by introducing a highly nonlinear fiber (HNLF) in an erbium-doped fiber ring laser (EDFRL). A broadband spectrum of ~ 39 nm in the L-band and ~ 21 nm in the C-band were obtained at pump powers as low as ~ 200 mW with appropriate optimizations. Demultiplexed output from the broadband generated in the C-band region is tested for wavelength and power stability for consideration as a suitable source for various applications. The wavelength and power fluctuations have been observed to be at most ~ 0.02 nm and ~ 0.3 dBm, respectively. | We report 100-channel transmission of both C- and l-band with 765 Gb/s capacity over a distance of 2,000 km. To achieve this transmission result, we utilized dispersion flattened transmission and broadband medium gain erbium doped fiber amplifiers. | eng_Latn | 7,606 |
A terahertz quantum cascade laser and an integrated Auston-switch are coupled to perform ultrafast gain switching. The resulting non-equilibrium gain is not clamped above laser threshold and large amplification of input terahertz pulses is demonstrated. | We have been using the principles of injection-seeded terahertz parametric generation (TPG) to develop the terahertz parametric amplifier (TPA) since 2014. Although we previously achieved amplification of 55 dB at 1.6 THz, amplification of low-frequency terahertz waves (≤1 THz) or ultraweak inputs was difficult, because broadband terahertz waves (spontaneous TPG) were generated and interfered with amplification. Thus, we herein present a new technique that divides terahertz-wave amplification into two steps: preamplification and main amplification. In this configuration, the terahertz wave is upconverted to a near-infrared (NIR) beam. Then, the noise is removed under the NIR condition and converted again to terahertz waves by the main amplifier. This two-stage TPA affords an extremely high amplification factor (up to six-billion-fold; 98 dB) for an ultraweak input of 500 zJ (zJ = 10−21 J). This is the first amplifier that has such a high gain for sub-aJ order input in the terahertz region. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,607 |
Twist of coherent fields and beam quality | Propagation invariant laser beams for optical metrology applications | Completely Stale Transmitter Channel State Information is Still Very Useful | eng_Latn | 7,608 |
Polaron effects on the linear and nonlinear intersubband optical absorption coefficients in quantum wells with asymmetrical semi-exponential potential | Electric-field-induced Nonlinear Optical Rectification, Second- and Third-harmonic Generation in Asymmetrical Quantum Well | Absence of CCR8 does not impair the response to ovalbumin-induced allergic airway disease. | eng_Latn | 7,609 |
Tunable mid-infrared (6.3-12 μm)optical vortex pulse generation. | Mid-infrared optical vortex parametric laser with topological charge versatility | Oral insulin does not alter gut microbiota composition of NOD mice | eng_Latn | 7,610 |
Defect enhanced silicon-on-insulator microdisk photodetector | Two-photon absorption photocurrent in p-i-n diode embedded silicon microdisk resonators | Digital Flicker-Free Slow Scan Multispectral Imagery Display | eng_Latn | 7,611 |
Control of Wavelength, Polarization, Time-Structure and Divergence for Synchrotron Radiation Topography | Characterization Of The Absolute Photon Sensitivity Of Gold Cathode Photoelectric Detectors | Completely Stale Transmitter Channel State Information is Still Very Useful | eng_Latn | 7,612 |
How short are ultra short light pulses? (looking back to the mid sixties) | Transient stimulated Raman scattering in liquids and evaluation of picosecond pulse duration | Ultrashort pulse laser ionization microscopy | eng_Latn | 7,613 |
Energy recycling versus lifetime quenching in erbium-doped 3-μm fiber lasers | Experimental and Numerical Investigations on Q-Switched Laser-Seeded Fiber MOPA at 2.8 μm | Large Energy, Wavelength Widely Tunable, Topological Insulator Q-Switched Erbium-Doped Fiber Laser | eng_Latn | 7,614 |
New class of two-photon-absorbing chromophores based on dithienothiophene | Resonant and static cubic hyperpolarizabilities of push-pull dipolar and quadrupolar chromophores: toward enhanced two-photon absorption | Delayed Reactive Distractor Suppression in Aging Populations | eng_Latn | 7,615 |
"Photonic lantern" spectral filters in multi-core Fiber. | Analysis of multi-mode to single-mode conversion at 635 nm and 1550 nm | Autologous immune responses to the major oncornavirus polypeptides in unmanipulated AKR/J mice. | eng_Latn | 7,616 |
Dispersion-managed mode locking | Dispersion-managed breathing-mode semiconductor mode-locked ring laser: experimental and numerical study | Dispersion-managed breathing-mode semiconductor mode-locked ring laser: experimental and numerical study | eng_Latn | 7,617 |
Explicit form for the kernel operator matrix elements in eigenfunction basis of harmonic oscillator | Extended Wigner function for the harmonic oscillator in the phase space | Transcriptional activation of HIF-1 by a ROS-ERK axis underlies the resistance to photodynamic therapy | eng_Latn | 7,618 |
A novel scheme of all optical header extraction for optical packet switching network | Header extraction with SOA-MZI in optical packet networks | 5-HT3 receptor ligands lack modulatory influence on acetycholine release in rat entorhinal cortex | eng_Latn | 7,619 |
Cycle Slip Compensation with Polarization Block Coding for Coherent Optical Transmission: Two-dimensional phases constellation corresponds to a slip state | A spatially-coupled type LDPC Code with an NCG of 12 dB for optical transmission beyond 100 Gb/s | Completely Stale Transmitter Channel State Information is Still Very Useful | eng_Latn | 7,620 |
Frequency locking of 1.5 mu m DFB laser diode to a neon indicator lamp using the optogalvanic effect | Photonic technologies and subsystems for terabit communications | Analysis of 37-kW Converter-Fed Induction Motor Losses | eng_Latn | 7,621 |
NDIR Ethanol Gas Sensor with Two Elliptical Optical Structures | Effects of Infrared Energy on Dual Elliptical NDIR Ethanol Gas Sensors | Effects of Infrared Energy on Dual Elliptical NDIR Ethanol Gas Sensors | eng_Latn | 7,622 |
Nonlinear Evolution of Lower-Hybrid Drift Instability in Harris Current Sheet | Electron dynamics in collisionless magnetic reconnection | Ultrastable optical clock with neutral atoms in an engineered light shift trap | kor_Hang | 7,623 |
QEPAS Sensor for Simultaneous Measurements of H2O, CH4, and C2H2 Using Different QTFs | Wavelength modulation technique-based photoacoustic spectroscopy for multipoint gas sensing. | Microtubule capture by CENP-E silences BubR1-dependent mitotic checkpoint signaling | eng_Latn | 7,624 |
Industrial Application Of Far-Infrared Lasers | The Failure Rate Of Polyethylene Insulated Cable | Resistance to a protein farnesyltransferase inhibitor in Plasmodium falciparum. | eng_Latn | 7,625 |
Zero-order diffractive microstructures for security applications | Leaky-mode resonance photonics: an applications platform | Noise-robust coherent diffractive imaging with a single diffraction pattern | eng_Latn | 7,626 |
Characteristics of a wavelength-switching fiber laser source | Intra-cavity polarization switching in optical fiber lasers | 5-HT3 receptor ligands lack modulatory influence on acetycholine release in rat entorhinal cortex | eng_Latn | 7,627 |
NIRSpec - an IR spectrometer for the James Webb Space Telescope | The James Webb Space Telescope science instrument suite: an overview of optical designs | Microtubule capture by CENP-E silences BubR1-dependent mitotic checkpoint signaling | eng_Latn | 7,628 |
Broadband spectroscopic lidar for SWIR/MWIR detection of gaseous pollutants in air | Enhancements to INO's broadband SWIR/MWIR spectroscopic lidar | Enhancements to INO's broadband SWIR/MWIR spectroscopic lidar | eng_Latn | 7,629 |
Design and cost performance of WDM PONs for multi-wavelength users | Crosstalk and loss in wavelength division multiplexed systems employing spectral slicing | No-Guard-Interval Coherent Optical OFDM for 100-Gb/s Long-Haul WDM Transmission | eng_Latn | 7,630 |
Electrically pumped photonic nanowire single-photon source with an efficiency of 89% | Designs for high-efficiency electrically pumped photonic nanowire single-photon sources | Designs for high-efficiency electrically pumped photonic nanowire single-photon sources | eng_Latn | 7,631 |
Linear Variable Filter Based on a Gradient Grating Period Guided-Mode Resonance Filter | Leaky-mode resonance photonics: an applications platform | Full polarimetric GPR antenna system aboard the ExoMars rover | eng_Latn | 7,632 |
Sub-THz Photonic-Transmitters Based on Separated-Transport-Recombination Photodiodes and a Micromachined Slot Antenna | Increase in response time of low-temperature-grown GaAs photoconductive switches at high voltage bias | Completely Stale Transmitter Channel State Information is Still Very Useful | eng_Latn | 7,633 |
Technology and Development of Free space Laser Communication | Tracing platform for infrared laser atmospheric communication between warships | Suppression of bremsstrahlung and pair production due to environmental factors | eng_Latn | 7,634 |
Simple self-seeding scheme for generation of wavelength-tunable optical short pulses | 20 nm wavelength tunable single mode picosecond pulse generation at 1.3 mu m by self-seeded gain-switched semiconductor laser | Completely Stale Transmitter Channel State Information is Still Very Useful | eng_Latn | 7,635 |
Improved Indirect Photon Mapping with Weighted Importance Sampling | Faster photon map global illumination | Transcriptional activation of HIF-1 by a ROS-ERK axis underlies the resistance to photodynamic therapy | eng_Latn | 7,636 |
The phase behavior of a weakly attractive colloidal system | Optical Manipulation of Microscale Fluid Flow | Highly coherent RF signal generation by heterodyne optical phase locking of external cavity semiconductor lasers | eng_Latn | 7,637 |
Lagged Coherence of Photon Emissions and Spectral Power Densities between the Cerebral Hemispheres of Human Subjects during Rest Conditions: Phase Shift and Quantum Possibilities | The Aharanov-Bohm Phase Shift and Magnetic Vector Potential “A” Could Accommodate for Optical Coupler, Digital-to-Analogue Magnetic Field Excess Correlations of Photon Emissions Within Living Aqueous Systems | Noise-robust coherent diffractive imaging with a single diffraction pattern | eng_Latn | 7,638 |
Using Optical Processing To Find The Beam Profile Of A Laser Pulse (Theory) | Laser beam profile measurements using spatial sampling, fourier optics, and holography | 101 Flux Decline in Ultrafiltration Processes | yue_Hant | 7,639 |
Ring and axis mode lasing in quasi-stadium laser diodes with concentric end mirrors | Enhancement of Laser Power Efficiency by Control of Spatial Hole Burning Interactions | SNARE Function Is Not Involved in Early Endosome Docking | eng_Latn | 7,640 |
Tunable, Ultrafast Fiber-Laser Between 1.15 and 1.35 μm for Harmonic Generation Microscopy in Human Skin | Deep tissue multiphoton microscopy using longer wavelength excitation | Numerical investigation of high-power single frequency fiber amplifiers at a wavelength of 1018nm | eng_Latn | 7,641 |
Single Passband Microwave Photonic Filter With Continuous Wideband Tunability Based on Electro-Optic Phase Modulator and Fabry–Pérot Semiconductor Optical Amplifier | Microwave photonics combines two worlds | Poor Agreement between Respiratory Variations in Pulse Oximetry Photoplethysmographic Waveform Amplitude and Pulse Pressure in Intensive Care Unit Patients | eng_Latn | 7,642 |
3.4-THz quantum cascade laser based on longitudinal-optical-phonon scattering for depopulation | The Use of Quantum Cascade Lasers as Local Oscillator for Heterodyne Detection of THz Radiation | Surface of localized pleural plaques quantitated by computed tomography scanning: no relation with cumulative asbestos exposure and no effect on lung function | eng_Latn | 7,643 |
Hollow optical-fiber based infrared spectroscopy for measurement of blood glucose level by using multi-reflection prism | Non-invasive blood glucose measurement using fixed-wavelength quantum cascade lasers | Automatic detection of objective prism stellar spectra | eng_Latn | 7,644 |
Numerical simulation of ultrafast expansion as the driving mechanism for confined laser ablation with ultra-short laser pulses | Layer-selective lift-off processing in a TCO/Si thin film system by ultra-short (ps, fs) laser pulses | 101 Flux Decline in Ultrafiltration Processes | eng_Latn | 7,645 |
6-mode spatial multiplexer with low loss and high selectivity for transmission over few mode fiber | Low insertion loss highly mode-selective spatial multiplexers using multi-plane light conversion | Low insertion loss highly mode-selective spatial multiplexers using multi-plane light conversion | eng_Latn | 7,646 |
We demonstrate efficient generation of narrowband (<; 100 GHz) THz pulses in the nanosecond range by using difference frequency generation in organic electro-optic crystals DSTMS and OH1. The terahertz output is tunable in the range of 1-20 THz and can be used for THz imaging and spectroscopy. | High-field terahertz (THz) single-cycle pulses with 1.5 MV/cm are generated by optical rectification in the stilbazolium salt crystal 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate. We show experimentally that the generated THz transient carrying 5 octaves (0.15 to 5.5 THz) undergoes a complex time-frequency evolution when tightly focused, and we present a model based on three independent oscillating dipoles capable to describe this anomalous field evolution. Finally, we present a method to control the absolute phase of such supercontinuum THz pulses as an essential tool for future field-sensitive investigations. | Using a recirculating loop, we measured nonlinearly induced timing jitter in a terrestrial wavelength-division-multiplexed system at different transmission distances with different amounts of precompensation. Within each 600-GHz subband, we achieved error-free transmission using the same amount of precompensation for all channels at all distances up to 5000 km. | eng_Latn | 7,647 |
A new approach for studying mixing and combustion phenomena in turbulent partially premixed flames using laser-induced breakdown spectroscopy (LIBS) is demonstrated. Setting the laser pulse energy just above the breakdown threshold in the cold gas allows statistical data to be obtained concerning the probability of finding cold or hot gas inside the measurement volume. Moreover, a compositional analysis utilizing the LIBS spectra allows the mixing of the different cold gas flows to be studied. A proof-of-concept experiment is carried out in a turbulent jet flame stabilized on a coaxial burner. The LIBS data agree well with results obtained by planar laser-induced fluorescence of OH radicals. | Time-gated picosecond laser-induced breakdown spectroscopy (ps-LIBS) for the determination of local equivalence ratios in atmospheric-pressure adiabatic methane–air flames is demonstrated. Traditional LIBS for equivalence-ratio measurements employ nanosecond (ns)-laser pulses, which generate excessive amounts of continuum, reducing measurement accuracy and precision. Shorter pulse durations reduce the continuum emission by limiting avalanche ionization. Furthermore, by contrast the use of femtosecond lasers, plasma emission using picosecond-laser excitation has a high signal-to-noise ratio (S/N), allowing single-shot measurements suitable for equivalence-ratio determination in turbulent reacting flows. We carried out an analysis of the dependence of the plasma emission ratio Hα (656 nm)/NII (568 nm) on laser energy and time-delay for optimization of S/N and minimization of measurement uncertainties in the equivalence ratios. Our finding shows that higher laser energy and shorter time delay reduces measurement uncertainty while maintaining high S/N. In addition to atmospheric-pressure flame studies, we also examine the stability of the ps-LIBS signal in a high-pressure nitrogen cell. The results indicate that the plasma emission and spatial position could be stable, shot-to-shot, at elevated pressure (up to 40 bar) using a lower excitation energy. Our work shows the potential of using ps-duration pulses to improve LIBS-based equivalence-ratio measurements, both in atmospheric and high-pressure combustion environments. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,648 |
We report on the observation and quantitative assessment of self-trapped pulsating beams in a highly nonlocal nonlinear regime. The experiments were conducted in nematic liquid crystals and allow a meaningful comparison with the prediction of a scalar theory in the perturbative limit, while addressing the need for beyond-paraxial analytical treatments. | Next-generation photonics envisions circuitry-free, rapidly reconfigurable systems powered by solitonic beams of self-trapped light and their particlelike interactions. Progress, however, has been limited by the need for reversibly responsive materials that host such nonlinear optical waves. We find that repeatedly switchable self-trapped visible laser beams, which exhibit strong pairwise interactions, can be generated in a photoresponsive hydrogel. Through comprehensive experiments and simulations, we show that the unique nonlinear conditions arise when photoisomerization of spiropyran substituents in pH-responsive poly(acrylamide-co-acrylic acid) hydrogel transduces optical energy into mechanical deformation of the 3D cross-linked hydrogel matrix. A Gaussian beam self-traps when localized isomerization-induced contraction of the hydrogel and expulsion of water generates a transient waveguide, which entraps the optical field and suppresses divergence. The waveguide is erased and reformed within seconds when the optical field is sequentially removed and reintroduced, allowing the self-trapped beam to be rapidly and repeatedly switched on and off at remarkably low powers in the milliwatt regime. Furthermore, this opto-chemo-mechanical transduction of energy mediated by the 3D cross-linked hydrogel network facilitates pairwise interactions between self-trapped beams both in the short range where there is significant overlap of their optical fields, and even in the long range––over separation distances of up to 10 times the beam width––where such overlap is negligible. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,649 |
Resonator-enhanced electro-optic (RE-EO) frequency comb generators produce broad combs by coupling an optical field to a resonator containing a phase modulator driven at a harmonic of the resonator free spectral range (FSR). Recent advances in integration technologies have opened up the possibility of fabricating low-loss, efficient, and tunable ring-based RE-EO comb generators. In this work, we analyze the properties of a canonical ring-based RE-EO comb generator and propose a new dual-ring comb generator to increase comb conversion efficiency, an especially important characteristic for comb-based optical communications systems. After a brief review of RE-EO comb generator properties in the case of resonant operation, i.e., when the optical frequency and the modulation frequency are harmonics of the resonator FSR, we analyze the effect of input optical phase noise and modulation phase noise on the resulting comb. Additionally, we show analytically that in non-resonant operation the optical frequency offset and the modulation frequency offset can be much larger than the linewidth of the resonator, increasing the tolerance to fabrication errors. Then, we develop and validate numerical models to predict the output spectrum in the presence of dispersive waveguides, which cannot be modeled analytically. Using these accurate models, we analyze a dual-ring RE-EO comb generator that uses a small coupling ring to increase the conversion efficiency to 32%, compared to the 1.3% efficiency of a single-ring RE-EO comb generator. We then analyze a point-to-point inter-data center optical link and determine that a dual-ring RE-EO comb generator can support high-capacity coherent links at 20 Tb/s per fiber. | We have demonstrated a method that efficiently transfers the power from a single-frequency laser into a wideband frequency comb. The comb was produced by a 2.7-GHz electro-optic modulator in a resonant optical cavity. A coupled cavity technique was used to transfer 8.5% of the laser power into a comb with a span of 400 modes, or more than 1 THz. | Background:Abnormal vascular reactivity and reduced expression of endothelial nitric oxide synthase (eNOS) gene are hallmark of salt-induced hypertension in rats. Although l-arginine is an establis... | eng_Latn | 7,650 |
We successfully demonstrate the effectiveness of a planar lightwave circuit (PLC) optical dispersion equalizer in a 2.5 Gb/s transmission experiment with a 40 km-long 1.3 /spl mu/m zero-dispersion fiber at 1.55 /spl mu/m. The dispersion equalizer consists of 5 Mach-Zehnder interferometers with asymmetrical arm lengths cascaded in series. The total insertion loss is 3.5 dB and the maximum dispersion value is 836 psec/nm in the 1.55 /spl mu/m region. > | An integrated-optic dispersion equalizer has been fabricated on a planar lightwave circuit (PLC) for the first time. The PLC optical dispersion equalizer can compensate for both negative and positive fiber dispersion values. In a preliminary experiment, we successfully compensated for the chromatic dispersion of a 20 km-long 1.3 /spl mu/m zero-dispersion fiber at 1.55 /spl mu/m. > | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,651 |
Confocal laser microscopy (CLM) is a powerful tool in life science research and industrial inspection because it offers two-dimensional optical sectioning or three-dimensional imaging capability with micrometer depth selectivity. Furthermore, scan-less imaging modality enables rapid image acquisition and high robustness against surrounding external disturbances in CLM. However, the objects to be measured must be reflective, absorptive, scattering, or fluorescent because the image contrast is given by the optical intensity. If a new image contrast can be provided by the optical phase, scan-less CLM can be further applied for transparent non-fluorescent objects or reflective objects with nanometer unevenness by providing information on refractive index, optical thickness, or geometrical shape. Here, we report scan-less confocal dual-comb microscopy offering a phase image in addition to an amplitude image with depth selectivity by using an optical frequency comb as an optical carrier of amplitude and phase with discrete ultra-multichannels. Our technique encodes confocal amplitude and phase images of a sample onto a series of discrete modes in the optical frequency comb with well-defined amplitude and phase to establish a one-to-one correspondence between image pixels and comb modes. The technique then decodes these images from comb modes with amplitude and phase. We demonstrate confocal phase imaging with milliradian phase resolution under micrometer depth selectivity on the millisecond timescale. As a proof of concept, we demonstrate the quantitative phase imaging of standing culture fixed cells and the surface topography of nanometer-scale step structures. Our technique for confocal phase imaging will find applications in three-dimensional visualization of stacked living cells in culture and nanometer surface topography of semiconductor objects. | A laser frequency comb is a broad spectrum composed of equidistant narrow lines. Initially invented for frequency metrology, such combs enable new approaches to spectroscopy over broad spectral bandwidths, of particular relevance to molecules. The performance of existing spectrometers — such as crossed dispersers employing, for example, virtual imaging phase array etalons, or Michelson-based Fourier transform interferometers — can be dramatically enhanced with optical frequency combs. A new class of instruments, such as dual-comb spectrometers without moving parts, enables fast and accurate measurements over broad spectral ranges. The direct self-calibration of the frequency scale of the spectra within the accuracy of an atomic clock and the negligible contribution of the instrumental line-shape will enable determinations of all spectral parameters with high accuracy for stringent comparisons with theories in atomic and molecular physics. Chip-scale frequency comb spectrometers promise integrated devices for real-time sensing in analytical chemistry and biomedicine. This Review gives a summary of the developments in the emerging and rapidly advancing field of atomic and molecular broadband spectroscopy with frequency combs. Frequency comb spectroscopy is a recent field of research that has blossomed in the past five years. This Review discusses developments in the emerging and rapidly advancing field of atomic and molecular broadband spectroscopy with frequency combs. | Perfect Quantum Cloning Machines (QCM) would allow to use quantum nonlocality for arbitrary fast signaling. However perfect QCM cannot exist. We derive a bound on the fidelity of QCM compatible with the no-signaling constraint. This bound equals the fidelity of the Bu\v{z}ek-Hillery QCM. | eng_Latn | 7,652 |
A technique for the experimental implementation of fully complex filters with commercially available spatial light modulators (SLMs) is reported. The filters are incorporated into an all-optical correlator and a hybrid digital-optical correlator, the relative merits of each configuration being considered. Various filter functions requiring complex modulation are demonstrated, consideration being given to the degradation of filter performance due to the limited quantisation and dynamic range with which they can be implemented using current SLM technology. | Two-dimensional correlation between a reference template and an input scene is a powerful pattern recognition technique but is demanding of computational power. Coherent optical correlators, exploiting the Fourier transforming properties of a lens and the capability to impart a phase modulation on a wavefront with an appropriate spatial light modulator (SLM), hold the promise of real-time implementation of two- dimensional correlation for realistic pattern recognition problems. However, their practical use has been delayed in many applications by the lack of availability of suitable SLM devices with the required speed and dynamic range, with different needs for input and frequency plane modulators. It is now possible to compute a two-dimensional Fourier transform at video-rates with various digital signal processing chip sets. Thus a hybrid correlator is proposed in which the input scene is digitally Fourier transformed at video-rate, and multiple templates searched during the next video frame interval by optical mixing and Fourier transformation at a speed at least two orders of magnitude faster than possible with digital methods. In this way, the input SLM is avoided and a precise spectrum is available for subsequent digital or optical mixing with the stored templates. The speed advantage over all-digital processing allows unconstrained pattern recognition problems to be tackled that require many template searches to match the input with a reference function. Different hybrid correlator configurations are considered, together with discussion of the various digital chip sets available to perform the video-rate FFT, as well as the SLM devices currently available that are suitable as frequency domain phase modulators.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,653 |
Solid state laser (SSL) powers can be realistically scaled when pumped by a real, efficient and multimode pulse. In this work, a fourth-order super-Gaussian pulse was assumed as a pump for SSL’s and a complete analytical expression for the thermal phase shift is given. Moreover, the focal length of thermal lens in paraxial ray approximation regime was studied. The results when applied to a Ti: sapphire crystal show an appreciable correction for abberation compared to a top-hat pulse. | Based on the actual working environment of pulse LD dual-end pumped Tm:YAG crystal, time-dependent temperature field analytical expression and the time-varying thermal focal length are deduced by the integral transform method. Additionally, the effects of pump power, repetition frequency and duty ratio on axial transient temperature distribution and time-varying thermal focal length of pulse LD dual-end pumped Tm:YAG rod are simulated and analyzed. The results show that the temperature distribution reaches steady state respectively by 11, 14, 15 pulses under pump power of 30W, 35W and 40W, respectively, while the frequency is 100Hz and the duty ratio is 50%. Under the condition mentioned above, the temperature of the crystal rod on both ends of the center arrives 34.7°C, 37.5°C, 40.3°C, which is 1.8°C, 2.1°C, 2.4°C higher than the center of rod. And the thermal focal length is in the range of 31.5-41.5cm, 26.5-34.6cm, 22.9-29.7cm, respectively. When pump energy is 100mJ, frequency at 110Hz, 120 Hz, 130Hz and duty ratio at 55%, 60%, 65%, respectively, the temperature distribution reaches steady state respectively by 13, 15, 16 pulses, and the temperature of the rod on both ends of the center respectively arrives 30.0°C, 30.9°C, 31.8°C, which is 1.3°C, 1.4°C, 1.5°C higher than the center of rod, and thermal focal length is in the range 46.4-58.8cm, 42.7-51.6cm, 39.5-45.9cm, respectively. Namely, as the increase of the pulses number, the distribution of the temperature and the thermal focal length in crystal rod appear jagged and eventually get to the periodic distributions. With the increase of the pump power, repetition frequency and duty ratio, the temperature difference between the crystal rod on both ends of the center and the center of rod is increasing, while time-varying thermal focal length gradually becomes shorter and the fluctuation range is smaller until it reaches steady state. The results provide theoretical basis for heating compensation and cavity design of pulsed thulium doped lasers. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,654 |
Continuous advances in low-cost MANPAD heat-seeking missile technology over the past 50 years remains the number one hostile threat to airborne platforms globally responsible for over 60 % of casualties. Laser based directional countermeasure (DIRCM) technology have been deployed to counter the threat. Ideally, a laser based DIRCM system must involve a number of lasers emitting at different spectral bands mimicking the spectral signature of the airborne platform. Up to now, near and mid infrared spectral bands have been covered with semiconductor laser technology and only SWIR band remained with bulky fiber laser technology. Recent technology developments on direct-diode GaSb laser technology at Brolis Semiconductors offer a replacement for the fiber laser source leading to significant improvements by few orders of magnitude in weight, footprint, efficiency and cost. We demonstrate that with careful engineering, several multimode emitters can be combined to provide a directional laser beam with radiant intensity from 10 kW/sr to 60 kW/sr in an ultra-compact hermetic package with weight < 30 g and overall efficiency of 15 % in the 2.1- 2.3 micron spectral band offering 150 times improvement in efficiency and reduction in footprint. We will discuss present results, challenges and future developments for such next-generation integrated direct diode DIRCM modules for SWIR band. | Compact high-power 2100 nm laser diode module for next-generation directional infrared countermeasure (DIRCM) systems is presented. Next-generation DIRCM systems require compact, light-weight and robust laser modules which could provide intense IR light emission capable of disrupting the tracking sensor of heat-seeking missile. Currently used solid-state and fiber laser solutions for mid-IR band are bulky and heavy making them difficult to implement in smaller form-factor DIRCM systems. Recent development of GaSb laser diode technology greatly improved optical output powers and efficiencies of laser diodes working in 1900 - 2450 nm band [1] while also maintaining very attractive size, weight, power consumption and cost characteristics. 2100 nm laser diode module presented in this work performance is based on high-efficiency broad emitting area GaSb laser diode technology. Each laser diode emitter is able to provide 1 W of CW output optical power with working point efficiency up to 20% at temperature of 20 °C. For output beam collimation custom designed fast-axis collimator and slow-axis collimator lenses were used. These lenses were actively aligned and attached using UV epoxy curing. Total 2 emitters stacked vertically were used in 2100 nm laser diode module. Final optical output power of the module goes up to 2 W at temperature of 20 °C. Total dimensions of the laser diode module are 35 x 25 x 16 mm (L x W x H) with a weight of ~28 grams. Finally output beam is bore-sighted to mechanical axes of the module housing allowing for easy integration into next-generation DIRCM systems. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 7,655 |
Ultraviolet scattering communication provides none-line-of-sight connectivity for two separated transceivers, but it is limited by low emitting power and high atmospheric absorption in long-range case. This paper adopts a Monte Carlo based multiple-scattering model, and studies associated power losses of optical signals from ultraviolet to visible and infrared bands. Aerosol scattering and absorption coefficients dependent on wavelength are calculated, and wide-spectra Mie phase function is further derived. Data rates at different wavelengths are analytically compared under a specified bit error rate with daytime background light considered. Simulation results reveal that visible and infrared light have low path loss and high data rate advantages in long-range scattering communication. | Non-line-of-sight (NLOS) optical wireless communications using ultraviolet radiation and relying on atmospheric scattering has been proposed for short-range non-line-of-sight connectivity. Compared with single-input single-output (SISO) systems, single-input multiple-output (SIMO) communication systems can offer receiver diversity in channels that have faded due to turbulence. However, the portion of the transmission path from the transmitter and the scattering volume is shared by the multiple channels, leading to channel gain correlations and thus degraded system performance. In this paper, we first study the channel correlations under log-normal and gamma-gamma turbulence, both analytically and numerically. Then, we investigate the outage probability based on the channel capacity. Due to scattering, the results are observed to be significantly different from traditional line-of-sight free-space optical communications. For a communication system with one transmitter and two receivers, the subchannel correlation coefficient can be more than 0.8 for two receivers, even if they are separated by several meters. The proposed model can well characterize the outage probability, especially for small transmission beam widths. | Fluorescence imaging in vivo is hampered by autofluorescence and the scattering and absorption of short-wavelength light. To address these problems, Xiong et al. produce self-luminescing nanoparticles that enable in vivo near-infrared imaging without external light excitation. | eng_Latn | 7,656 |
Photoacoustic imaging (PAI) has many interesting advantages, such as deep imaging depth, high image resolution, and high contrast to intrinsic and extrinsic chromophores, enabling morphological, functional, and molecular imaging of living subjects. Photoacoustic microscopy (PAM) is one form of the PAI inheriting its characteristics and is useful in both preclinical and clinical research. Over the years, PAM systems have been evolved in several forms and each form has its relative advantages and disadvantages. Thus, to maximize the benefits of PAM for a specific application, it is important to configure the PAM system optimally by targeting a specific application. In this review, we provide practical methods for implementing a PAM system to improve the resolution, signal-to-noise ratio (SNR), and imaging speed. In addition, we review the preclinical and the clinical applications of PAM and discuss the current challenges and the scope for future developments. | Super-resolution microscopy based on light-activated atomic force microscopy has been demonstrated a team in Korea. The diffraction limit makes it difficult to image structures smaller than about 200 nanometres using optical microscopy. While several super-resolution fluorescence microscopy techniques have been realized, there is a need for a super-resolution technique that does not use fluorescent dyes. Chulhong Kim of Pohang University of Science and Technology in Korea and co-workers have realized a resolution of 8 nanometres by using a pulsed laser beam to optically excite a sample and then observing the response using a conventional atomic force microscope. The researchers demonstrated their system by using it to image single gold nanoparticles as well as cancer and plant cells. They anticipate that it could find use in fields as diverse as physics, biology, chemistry, medicine and material science. | Perfect Quantum Cloning Machines (QCM) would allow to use quantum nonlocality for arbitrary fast signaling. However perfect QCM cannot exist. We derive a bound on the fidelity of QCM compatible with the no-signaling constraint. This bound equals the fidelity of the Bu\v{z}ek-Hillery QCM. | eng_Latn | 7,657 |
The key stream generated from Line Feedback Shift Register (LFSR) has short period and does not suit encrypting plentiful information. At the same time, chaotic sequences are prone to become short periodic ones because of the restriction of computational precision of computers. Aiming at remedying these inadequacies, a new design of the Feedback Shift Register (FSR) based on chaotic maps was put forward. Through simulation and analysis, the favorable performances of the binary sequences got from our method are evaluated. | According to the structure analysis of Portable Execute File and its own characteristics, a software watermark framework model was put forward. By adding a new section used for storing control code and extracting feature information from the original PE file, the unique watermark marking for the software copyright was produced. After encryption, being divided, based on the assembled table, the watermark was embedded into the redundant space of each section. And then by means of abstract extraction from certain parts, it is helpful to further verify the integrity of PE file. Simulation shows that the algorithm framework model has a higher protection capacity for software copyright. | We present a new detection instrument for sensor measurements based on excited-state fluorescence lifetimes. This system consists of a primary optoelectronic loop containing a resonance-type rf amplifier, a modulatable fluorescence-excitation light source, a fiber optic feedback loop (with a gap for a fluorescent sensor), and a photomultiplier tube. A secondary, phase-feedback optoelectronic circuit consists of a long-wavelength-pass optical filter, a second photomultiplier tube, a photodiode, an electronic phase detector, a dc amplifier, and an electronic phase shifter (inserted into the main loop). This phase-feedback circuit is new with respect to our previous work. Under the appropriate conditions, the main loop exhibits self-oscillations, manifesting themselves as sinusoidal rf modulation of light intensity. The phase-feedback circuit detects the modulation phase shift resulting from the finite excited-state lifetimes of a fluorophore. As the excited state lifetime changes, the phase shift from the electronic phase shifter also changes, which results in a shift in self-oscillation frequency. The detection system uses self-oscillation frequency as the detection parameter and has excellent resolution with respect to changes in excited-state lifetime (~1 ps). | eng_Latn | 7,658 |
The quality-factor dependent enhancement of the field of a weak probe laser beam inside a resonant optical cavity is used to measure the minute optical absorption of liquid films, metallic and high reflectivity dielectric coatings. The measurement is not affected by the presence of the surface reflections and the scattering from the strong pump laser beam, which is focussed onto the sample placed inside the cavity. Laser surface heating calculations were performed and account qualitatively for both the spatial and temporal behavior of the observed signals. | Three different techniques for signal amplification utilizing, cavity resonances are examined. Cavity-enhanced photothermal spectroscopy and cavity-enhanced photovaporization spectroscopy are based on resonator optical cavities and cavity-enhanced capillary wave spectroscopy is based on a mechanical resonator. The signal amplification can make feasible the measurement of small effects which would otherwise be obscured by noise. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,659 |
Injection-seeded terahertz (THz)-wave parametric generation pumped by subnanosecond pulses was demonstrated as an exploration of the effective pump pulse width. In experiments, pump sources with different pump widths of 35–850 ps were used. The relationship between the undesirable effect of stimulated Brillouin scattering (SBS) and the THz-wave output in LiNbO3 was analyzed. The transient effect on SBS was not actualized around the acoustic phonon lifetime of LiNbO3. Pump widths below 420 ps were found to provide THz-wave generation with an energy conversion efficiency of 10−4. With a pump width of 700 ps, which is around five phonon lifetimes, the conversion efficiency was decreased about one order of magnitude from that of the pump width of 420 ps. Additionally, the peak power of the THz-wave output was maintained at about 15 kW with an actual range of 10–20 kW below 200 ps. A continuous change in the THz-wave pulse energy was obtained for six-fold energy scaling from 100 to 600 nJ. | Generation of near single-cycle pulses centered at 0.5THz frequency with up to 10μJ energy, 100μW average power, and 5.0MW peak power was demonstrated by tilting the intensity front of a femtosecond optical pump pulse from a 10Hz Ti:sapphire laser to match the phonon-polariton phase velocity to the group velocity of the pump pulses in a lithium niobate crystal. Terahertz pulse intensity as high as 10MW∕cm2 was achieved. The photon conversion efficiency was 45% and the calculated peak electric field strength at the focus of an off-axis parabolic mirror was 250kV∕cm. | An injection-locking-based pump recovery system for phase-sensitively amplified links is proposed and studied experimentally. Measurements with 10 Gbaud DQPSK signals show penalty-free recovery of 0.8 GHz FWHM bandwidth pump with 63 dB overall amplification. | eng_Latn | 7,660 |
A hybrid scheme for analogue-to-digital conversion (ADC) is described in which electro-optic techniques are employed to reduce the timing jitter which is a primary factor in restricting the resolution obtainable in all-electronic ADCs. The proposed system uses commercially available digitisers and optical components together with a specially designed, optically triggered sample-and-hold circuit realised in GaAs MESFET technology. A novel technique is described by means of which up to 20 parallel, interleaved ADC paths can be driven from a single mode-locked laser source. Estimated performance limits are provided. | An experiment in which a high-power mode-locked femtosecond semiconductor laser system was used as a source of extremely low jitter intense optical pulses in the distribution of a clock to 1024 ports via optical fibers is described. The total accumulated dynamic clock jitter between any two ports, which contains both correlated and uncorrelated sources, was measured to be less than 12 ps. This laser system produced a train of 460-fs optical pulses with over 70 W of peak power at 302 MHz. These results represent the largest fanout with the minimum timing jitter for an optically distributed clocking network. > | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,661 |
We report on the use of an ultra-narrow (∼0.01 nm) spectrum-sliced incoherent light source for transmission of a 10-Gb/s non-return-to-zero signal over 20-km standard single mode fiber or 0.2-nm-bandwidth optical filter. | We investigate wideband reduction of excess intensity noise in incoherent light for application to spectrum-sliced WDM systems. The noise reduction scheme is based on optoelectronic feedforward compensation. We derive expressions for the probability density function of noise-reduced incoherent light and present measurements that are in good agreement with theory. We evaluate the significant levels of improvement obtainable in the capacity of spectrum-sliced WDM channels. For example, to obtain a signal-to-noise ratio of 50, a noise-reduced channel requires six times less optical bandwidth than a spectral slice without noise reduction. | We describe a new method for producing high power coherent light at 589 nm based on a scalable, passively mode-locked, Nd:YVO4 laser and a seeded optical parametric amplifier. Average powers of 4.6 W at 589 nm have been produced. | eng_Latn | 7,662 |
Tunable optofluidic devices exhibit some unique characteristics that are not achievable in conventional solid-state photonic devices. They provide exciting opportunities for emerging applications in imaging, information processing, sensing, optical communication, lab-on-a-chip and biomedical engineering. A dielectrophoresis effect is an important physical mechanism to realize tunable optofluidic devices. Via balancing the voltage-induced dielectric force and interfacial tension, the liquid interface can be dynamically manipulated and the optical output reconfigured or adaptively tuned in real time. Dielectrophoretically tunable optofluidic devices offer several attractive features, such as rapid prototyping, miniaturization, easy integration and low power consumption. In this review paper, we first explain the underlying operation principles and then review some recent progress in this field, covering the topics of adaptive lens, beam steering, iris, grating, optical switch/attenuator and single pixel display. Finally, the future perspectives are discussed. (Some figures may appear in colour only in the online journal) | A broadband beam steering device using the dielectrophoresis-tilted prism of liquids is demonstrated. Dielectric force is utilized to slant the interface to imitate the refractive behavior of a prism. The steering angle increases as the applied voltage increases. Two dimensional beam steering is also successfully achieved by stacking two devices in orthogonal positions. The broadband feature is demonstrated using two collinear green and red laser beams. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,663 |
The solar power system (SPS) is the most promising way to overcome global environmental and economic problems. Different SPS concepts are compared briefly. Direct conversion of solar energy to energy of a high-power laser beam has the advantage of high efficiency and precise energy transportation. Optical phase conjugation permits the use of acceptable cheap optics for energy transportation. Conversion of laser energy to electric energy is provided by photovoltaic cells. Technical consideration concerns the key components and features of the system. A space-based module of the system should satisfy several requirements. A thin-film large-scale collector should keep its form and must be oriented to the Sun. At the same time this collector should be transparent for the output laser beam. The laser should be aligned with the collector and with the receiving ground-based station. Optical phase conjugation can be fruitful using an appropriate reference beam. All-weatherness is the problem for energy transportation. These and other issues have been analyzed in the paper. The most interesting and important result arises from economic assessments. Preliminary analysis shows 1 kWe cost $300-500 and 1 kW-hr cost $0.002-0.003. We have estimated an R&D program and following, an expected minimum net profit $450-500 billion. Our general analysis shows that commercial electrical power supply for terrestrial consumers could be available in the following decade. | A process that involves the use of nonlinear optical effects to precisely reverse the direction of p… | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,664 |
Micro-optoelectromechanical systems (MOEMS) having valuable performance, size, and cost attributes offer novel solutions to the design of lightwave network elements. We will discuss the new challenges that realizing these benefits presents to the field of photonic packaging. | Increased traffic volume due to the introduction of new broadband services is driving carriersto the deployment of an optical transport layer based on Wavelength Division Multiplexing(WDM) [1]. The network infrastructure of existing core networks is currently undergoing atransformation from rings using SONET Add/Drop Multiplexers (ADMs) to mesh topologiesusing Optical Cross-connects (OXCs). A core optical network architecture can be opaque ortransparent. An opaque architecture means that the optical signal carrying traffic undergoesan Optical to Electronic to Optical (OEO) conversion at different places in the network. Atransparent architecture means that the optical signal carrying traffic stays in the opticaldomain from the time it is generated at the edge of the network until it leaves the network.Even though the applications driving thelarge scaledeployment of transparent optical switches are notcurrently in place (niche applications in today’s networks onlyuse a very small number of transparent switches), and the trafficdemand does notcurrently justify theuse of transparentswitches that are cost effective at very high bit rates,it is possible that atsome point in the futuretransparent switches may be deployed in the network. Based on thisassumption, this paper explores the technology issues and challenges that are associated with3D MEMS-based switch fabrics. These fabrics offer the most viable approach to makesingle-stage switch fabrics with large portcounts that can be used for thedeployment of transparent switches in the network.Figure illustrates the four different node architectures that can comprise a core optical1network. The first architecture shows a fixed patch panel. Fixed patch panels located betweenWDM systems with transponders are currently being replaced by opaque (OEO) switchingnodes (with electrical switch fabrics) as shown in architectureof Figure (b). This is an1 opaque network architecture, as the optical signal undergoes OEO conversions [2]. The thirdarchitecture shows a transparent (OOO) switch between WDM systems with transpondersthat iscomplemented by an OEO switch for drop traffic. This is once again an opaquenetwork architecture, as the optical signal undergoes OEO conversions at the WDM | Protein-energy malnutrition (PEM) is common in connection with chronic disease and is associated with increased morbidity and mortality. Because the risk of PEM is related to the degree of illness, the causal connections between malnutrition and a poorer prognosis are complex. It cannot automatically be inferred that nutritional support will improve the clinical course of patients with wasting disorders. We reviewed studies of the treatment of PEM in cases of chronic obstructive pulmonary disease, chronic heart failure, stroke, dementia, rehabilitation after hip fracture, chronic renal failure, rheumatoid arthritis, and multiple disorders in the elderly. Several methodologic problems are associated with nutrition treatment studies in chronically ill patients. These problems include no generally accepted definition of PEM, uncertain patient compliance with supplementation, and a wide range of outcome variables. Avail-able treatment studies indicate that dietary supplements, either alone or in combination with hormonal treatment, may have positive effects when given to patients with manifest PEM or to patients at risk of developing PEM. In chronic obstructive pulmonary disease, nutritional treatment may improve respiratory function. Nutritional therapy of elderly women after hip fractures may speed up the rehabilitation process. When administered to elderly patients with multiple disorders, diet therapy may improve functional capacity. The data regarding nutritional treatment of the conditions mentioned above is still inconclusive. There is still a great need for randomized controlled long-term studies of the effects of defined nutritional intervention programs in chronically ill and frail elderly with a focus on determining clinically relevant outcomes. | eng_Latn | 7,665 |
An MoTe2 saturable absorber (SA) was fabricated for mid-infrared laser operations. By using this type of home-made SA as a Q-switcher for an in-band pumped Er:YAG laser, stable pulse trains with an average output power of 1.14 W were obtained at an absorbed pump power of 10.51 W. The Q-switched pulse envelope had a repetition rate of 41.59 kHz and its pulse duration was measured to be 1.048 µs, corresponding to a pulse energy of 27.4 µJ and a peak power of 26.14 W. | Molybdenum telluride (MoTe2) has attracted renewed interest owing to their versatile applications, such as transistors, logic circuits, photovoltaic cells, photodetectors, sensors, and lasers. We demonstrate an all-optically tunable microfiber knot resonator (MKR) overlaid with MoTe2 nanosheets. The optical transmitted power (OTP), resonance wavelength, and extinction ratio of the MoTe2 coated MKR can be tuned using external incidence pump lasers (405, 450, and 660 nm). MKR with MoTe2 nanosheets has strong absorption in the visible regime and enhanced light–matter interaction, resulting in enhanced tuning efficiency. Assisted by thermo-optic effect and photon generated carriers, the intensity and the wavelength of the MKR can be simultaneously tuned. The tuning efficiencies of the OTP, resonance wavelength, and extinction ratio of the MKR are up to 0.5 dB/mW, 7.52 pm/mW, and 0.16 dB/mW, respectively. The response time is measured to be ∼3 ms. Theoretical simulations are performed for the MKR with and without MoTe2, which agree well with the experimental results. The advantages of this device are all-optical tuning, easy fabrication, all-fiber content, high tuning efficiency, and fast response. This all-optical tunable MKR can find applications in all-optical circuitry, all-optical modulator, multi-dimensionally tunable optical devices, etc. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,666 |
We report our initial results on certain aspects of the fabrication of opto-electronic devices based on nonlinear optical organic polymers. In particular, we report the fabrication of rib waveguides in the high-temperature structural polymer PBI, measurement of the third-order nonlinear optical susceptibility in a side-chain biphenyl liquid-crystal polymer, and the determination that the origin of the response is thermal. In addition, we describe the design of a narrowband electro-optic tunable notch filter and report the results of device modeling calculations to determine the expected performance. | A scheme for a five volt V(pi) ) nonlinear optical (NLO) polymer optoelectronic (OE) device is presented with the potential to realize an interaction length that is about an order of magnitude shorter than conventional five volt V(pi) ) NLO polymer OE devices. It utilizes available NLO polymer materials for the core layer and a conductive polymer material for the cladding layers. Since the cladding layer material is more conductive than the core material, most of the applied poling and modulation voltages is dropped across the core layer, rendering a more efficient device. Using an NLO polymer material with electrooptic (EO) coefficients of say 22 pm/V, it is feasible to demonstrate < 2 mm OE devices operating at TTL voltage levels. These small device sizes could lead to use within electronic multichip modules. In addition, since the majority of the poling voltage is dropped across the core layer, less voltage is required so that in-situ poling becomes possible.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | We demonstrate a peak transmission efficiency of −2.4dB between a standard optical fiber and a nanophotonic waveguide using a mechanically compliant polymer interface. We find a 1.5dB penalty over a 100nm bandwidth and all polarizations. | eng_Latn | 7,667 |
Light emitting diodes (LEDs) are excellent candidates for the applications requiring low noise light sources with wavelengths ranging from 200 nm to 900 nm. These applications include the detection of fluorescence from protein molecules excited with the ultraviolet (UV) light (200-300nm) for identifying miniscule amounts of hazardous biological pathogens. The detection system including the light source must exhibit low noise and high stability over tens of minutes. In comparison with xenon, tungsten halogen lamps, lasers, and other conventional UV sources, UV LEDs are more stable, have lower noise, are smaller, cheaper, and easier to use. We report on the low frequency fluctuations of the current and light intensity of LEDs (fabricated by SET, Inc.) with wavelengths ranging from 265nm to 340nm. The results are compared with the noise properties of the halogen lamps and other commercially available LEDs with the wavelengths of 375nm, 505nm and 740nm. We show that the LEDs fabricated by Sensor Electronic technology, Inc. are suitable for studying steady state and time-varying UV fluorescence of biological materials. The correlation coefficient between the current and light intensity fluctuations varies with the LED current and load resistance. This dependence is explained in terms of the contributions to the 1/f noise from the active region and from the LED series resistance. The noise level could be reduced by operating the LEDs at a certain optimum current level and by using a large external series resistance (in the current source driving mode). | The influence of the reflection coefficient of cleaved facets from a double heterostructure laser on the l/f noise in light output is investigated. The experimental noise results are obtained by partially embedding the laser in Canada balsam, resulting in a decrease of the reflection coefficient, and by evaporating an aluminum coating, which results in a fully reflecting facet. These experimental results are shown to be in full agreement with an extension of existing models proposed by Fronen and Vandamme (l988). The 1/f noise arising from fluctuations in the refractive index is calculated, and it is concluded that this noise is negligible compared to the bulk noise in semiconductor lasers. > | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 7,668 |
This paper describes the design, modeling, construction, and testing of a low-cost and compact (80 mm×50 mm) 1×5 wavelength-selective switch. The core beam-deflecting element of the switch is a nematic liquid crystal on silicon spatial light modulator. The switch is designed for coarse wavelength-division multiplexing wavelengths in order to bring the benefit of a low-cost, compact, and robust switching design toward the customer end in the access network. During the system development stage, a single optomechanical assembly was designed and prototyped using the three-dimensional printing technology. The experimental results show an insertion loss of −13.8±1.4 dB and a worst-case scenario crosstalk level of −24.8 dB. Approaches for enhancing the performance of the switch are analyzed and discussed. | High-resolution optical filters and wavelength selective switches are the essential components in the current and next-generation dynamic optical networks. A high-resolution programmable filter for telecom application is proposed and experimentally demonstrated based on a 4 k phase-only liquid crystal on silicon (LCoS) spatial light modulator. The tuning resolution, bandwidth, and power attenuation for each wavelength channel can be modulated independently by remote software control. For each channel, the center wavelength is tuned in the step of 7.5 $ \pm$ 1 pm and the 3 dB bandwidth achieves from 10 GHz to 3 THz. Furthermore, by multi-casting hologram design techniques for an LCoS, the power attenuation is adjusted from 0 dB to 30 dB with the step of 0.1 dB. The insertion loss is less than 6 dB across the entire C -band and 1.8 dB of it can be further improved by adopting an LCoS chip with smaller reflection loss. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,669 |
We numerically investigate the scaling behavior of midinfrared filaments at extremely high input energies. It is shown that, given sufficient power, kilometer-scale, low-loss atmospheric filamentation is attainable by prechirping the pulse. Fully resolved four-dimensional ($xyzt$) simulations show that, while in a spatially imperfect beam the modulation instability can lead to multiple hot-spot formation, the individual filaments are still stabilized by the recently proposed mechanism that relies on the temporal walk-off of short-wavelength radiation. | We have identified major paradigm shifts relative to near-IR filamentation when high power multiple terawatt laser pulses are propagated at mid-IR and long-IR wavelengths within key atmospheric transmission windows. Individual filaments at near-IR (800 nm) wavelengths typically persist only over tens of centimeters, despite the whole beam supporting them being sustained over about a Rayleigh range. In the important mid-IR atmospheric window (3.2 - 4 μm) optical carrier wave self-steepening (carrier shocks) tend to dominate and modify the onset of long range filaments. These shocks generate bursts of higher harmonic dispersive waves that constrain the intensity growth of the filament to well below the traditional ionization limit, making long range low loss propagation possible. For long wavelength pulses in the 8-12 μm atmospheric transmission window, many-electron dephasing collisions from separate gas species act to dynamically suppress the traditional Kerr self-focusing lens and leads to a new type of whole beam self-trapping over multiple Rayleigh ranges. This prediction is key, since strong linear diffraction at these wavelengths are the major limitation and normally requires large launch beam apertures. We will present simulation results that predict multiple Rayleigh range propagation paths for whole beam self-trapping and will also discuss some recent efforts to extend the HITRAN linear atmospheric transmission/refractive index database to include nonlinear responses of important atmospheric molecular constituents. | Channel Hot Carrier (CHC) degradation on uniaxially strained pMOS and nMOS samples with different S/D materials has been analyzed. The results show that the CHC damage is larger in the strained samples in comparison with the unstrained devices, and increases with the temperature. | eng_Latn | 7,670 |
A compact time-resolved near-IR fluorescence imager was constructed to obtain lifetime and intensity images of DNA sequencing slab gels. The scanner consisted of a microscope body with f/1.2 relay optics onto which was mounted a pulsed diode laser (repetition rate 80 MHz, lasing wavelength 680 nm, average power 5 mW), filtering optics, and a large photoactive area (diameter 500 microns) single-photon avalanche diode that was actively quenched to provide a large dynamic operating range. The time-resolved data were processed using electronics configured in a conventional time-correlated single-photon-counting format with all of the counting hardware situated on a PC card resident on the computer bus. The microscope head produced a timing response of 450 ps (fwhm) in a scanning mode, allowing the measurement of subnano-second lifetimes. The time-resolved microscope head was placed in an automated DNA sequencer and translated across a 21-cm-wide gel plate in approximately 6 s (scan rate 3.5 cm/s) with an accumulation time per pixel of 10 ms. The sampling frequency was 0.17 Hz (duty cycle 0.0017), sufficient to prevent signal aliasing during the electrophoresis separation. Software (written in Visual Basic) allowed acquisition of both the intensity image and lifetime analysis of DNA bands migrating through the gel in real time. Using a dual-labeling (IRD700 and Cy5.5 labeling dyes)/two-lane sequencing strategy, we successfully read 670 bases of a control M13mp18 ssDNA template using lifetime identification. Comparison of the reconstructed sequence with the known sequence of the phage indicated the number of miscalls was only 2, producing an error rate of approximately 0.3% (identification accuracy 99.7%). The lifetimes were calculated using maximum likelihood estimators and allowed on-line determinations with high precision, even when short integration times were used to construct the decay profiles. Comparison of the lifetime base calling to a single-dye/four-lane sequencing strategy indicated similar results in terms of miscalls, but reduced insertion and deletion errors using lifetime identification methods, improving the overall read accuracy. | Frequency domain fluorescence lifetime imaging is a powerful technique that enables the observation of subtle changes in the molecular environment of a fluorescent probe. This technique works by measuring the phase delay between the optical emission and excitation of fluorophores as a function of modulation frequency. However, high-resolution measurements are time consuming, as the excitation modulation frequency must be swept, and faster low-resolution measurements at a single frequency are prone to large errors. Here, we present a low cost optical system for applications in real-time confocal lifetime imaging, which measures the phase vs. frequency spectrum without sweeping. Deemed Lifetime Imaging using Frequency-multiplexed Excitation (LIFE), this technique uses a digitally-synthesized radio frequency comb to drive an acousto-optic deflector, operated in a cat's-eye configuration, to produce a single laser excitation beam modulated at multiple beat frequencies. We demonstrate simultaneous fluorescence lifetime measurements at 10 frequencies over a bandwidth of 48 MHz, enabling high speed frequency domain lifetime analysis of single- and multi-component sample mixtures. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 7,671 |
We extensively studied a cross-talk phenomenon that seriously deteriorates the high time-resolution of a multi-anode 16-channel linear array photo-multiplier tube (PMT); the dynode structures were modified to eliminate the cross-talk effect and to recover a time resolution of σ = 70 – 80 ps for single photons. The use of 16 anode signals of the modified PMT enabled us to attain σ = 12 ps for a small TOF counter of Cherenkov radiation. | We demonstrate diffraction limited multiphoton imaging in a massively parallel, fully addressable time-resolved multi-beam multiphoton microscope capable of producing fluorescence lifetime images with sub-50ps temporal resolution. This imaging platform offers a significant improvement in acquisition speed over single-beam laser scanning FLIM by a factor of 64 without compromising in either the temporal or spatial resolutions of the system. We demonstrate FLIM acquisition at 500 ms with live cells expressing green fluorescent protein. The applicability of the technique to imaging protein-protein interactions in live cells is exemplified by observation of time-dependent FRET between the epidermal growth factor receptor (EGFR) and the adapter protein Grb2 following stimulation with the receptor ligand. Furthermore, ligand-dependent association of HER2-HER3 receptor tyrosine kinases was observed on a similar timescale and involved the internalisation and accumulation or receptor heterodimers within endosomes. These data demonstrate the broad applicability of this novel FLIM technique to the spatio-temporal dynamics of protein-protein interaction. | Coherent optical modems have been implemented that provide low cost 40 Gb/s connections over any optical line that can support 10 Gb/s transmission. CMOS signal processing allows performance substantially independent of PMD and optical dispersion. | eng_Latn | 7,672 |
2.3 dB of amplitude squeezing has been observed in a semiconductor laser with light injection from a single-mode semiconductor laser to one of the longitudinal modes of the slave laser. The slave laser operates as a semiconductor laser amplifier and oscillates at the injected mode, which differs from the free-running oscillation modes. | An injection-locking-based pump recovery system for phase-sensitively amplified links is proposed and studied experimentally. Measurements with 10 Gbaud DQPSK signals show penalty-free recovery of 0.8 GHz FWHM bandwidth pump with 63 dB overall amplification. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 7,673 |
With the ongoing steady traffic increase in the Internet, the wavelength usage of the supporting optical networks is a critical network efficiency parameter. Therefore, this paper suggests a way how to efficiently and economically achieve this goal in the context of optical burst switching, a very promising technology that has been proposed to overcome the shortcomings of conventional WDM deployment, such as lack of fine bandwidth granularity in wavelength routing and electronic speed bottlenecks in the presence of bursty traffic. In order to mitigate the burst loss and achieve high network efficiency we adapt the loss-less paradigm defined by Coutelen et al. (2010), i.e., the CAROBS framework. In classical OBS networks, the streamline effect ensures a very low level of contention, i.e., efficient transmission, hence we define a routing guided only by the streamline effect. The resulting routing problem is formulated as an optimization model which is solved using a decomposition technique to increase the scalability of the solution process. | Increase of bandwidth demand in data networks, driven by the continuous growth of the Internet and the increase of bandwidth greedy applications, raise the issue of how to support all the bandwidth requirements in the near future. Three optical switching paradigms have been defined and are being investigated: Optical Circuit Switching (OCS); Optical Packet Switching (OPS); and Optical Burst Switching (OBS). Among these paradigms, OBS is seen as the most appropriate solution today. However, OBS suffers from high burst loss as a result of contention in the bufferless mode of operation. This issue was investigated by Coutelen et al., 2009 who proposed the loss-free CAROBS framework whereby signal convertors of the optical signal to the electrical domain ensure electrical buffering. Convertors increase the network price which must be minimized to reduce the installation and operating costs of the CAROBS framework. ::: An analysis capturing convertor requirements, with respect to the number of merging flows and CAROBS node offered load, was carried out. We demonstrated the convertor location significance, which led to an additional investigation of the shared wavelength convertors scenario. Shared wavelength convertors significantly decrease the number of required convertors and show great promise for CAROBS. Based on this study we can design a CAROBS network to contain a combination of simple and complex nodes that include none or some convertors respectively, a vital feature of network throughput efficiency and cost. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,674 |
We propose and demonstrate an all-optical scheme of phase noise reduction using optical nonlinearity and dispersion/conversion delay. This scheme is capable of reducing the standard deviation of phase noise with low frequency component (e.g., laser phase noise) by a factor of ~ 4 without degrading the data signal. The EVM can be reduced from 31% to 11% for ~500 MHz phase noise bandwidth on 20-Gbaud QPSK input. | We propose and demonstrate tunable homodyne detection using nonlinear optical signal processing to automatically lock a “local” pump laser to an incoming 20-to-40-Gbaud QPSK data signal. Open eyes are obtained for both in-phase and quadrature components of the signal after ~200km transmission over SMF-28 and DCF fibers. The BER performance of the proposed homodyne detection scheme is also compared with the conventional intradyne receiver. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 7,675 |
We present the theory for an experimental verification of a new technique to combine multiple microwave signals populating a wide spectrum into a single, small band for further relay or processing. The method is an extension of well-known RF-over-fiber downconversion techniques but with multiple local oscillators (LOs) to translate widely spaced signals to intermediate frequencies that are within a single, narrower, spectral band. One dual-drive Mach–Zehnder modulator is used as two parallel phase modulators with the LOs presented to one RF drive and the signals to the other. This parallel arrangement adds, rather than multiplies, the LO tones and signals, eliminating a number of cross-modulation spurs that could otherwise make it very difficult to receive only the signals of interest. We verify the link’s performance by downconverting two widely spaced $K$ -band signals to $C$ -band while simultaneously relaying an existing $C$ -band signal on the same link and demodulating all three signals. | We present a new intensity-modulated analog optical link architecture in which a pulsed optical carrier replaces the standard low-noise continuous-wave laser. Through a time-domain analysis of the sampled link architecture, we show that the link performance metrics reduce to those of a conventional analog optical link in the absence of photodiode nonlinearity. Experimental measurements of the link gain and third-order nonlinearity are presented, emphasizing the link performance as a function of received photocurrent. The work presented here demonstrates that the performance of sampled analog optical links rivals that of the conventional architecture, even in the presence of significant photodiode nonlinearity. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,676 |
We present a new class of single-photon devices for counting of both visible and infrared photons. Our superconducting single-photon detectors (SSPDs) are characterized by the intrinsic quantum efficiency (QE) reaching up to 100%, above 10 GHz counting rate, and negligible dark counts. The detection mechanism is based on the photon-induced hotspot formation and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-wide superconducting stripe. The devices are fabricated from 3.5-nm-thick NbN films and operate at 4.2 K, well below the NbN superconducting transition temperature. Various continuous and pulsed laser sources in the wavelength range from 0.4 μm up to >3 μm were implemented in our experiments, enabling us to determine the detector QE in the photon-counting mode, response time, and jitter. For our best 3.5-nm-thick, 10×10 μm2-area devices, QE was found to reach almost 100% for any wavelength shorter than about 800 nm. For longer-wavelength (infrared) radiation, QE decreased exponentially with the photon wavelength increase. Time-resolved measurements of our SSPDs showed that the system-limited detector response pulse width was below 150 ps. The system jitter was measured to be 35 ps. In terms of the counting rate, jitter, and dark counts, the NbN SSPDs significantly outperform their semiconductor counterparts. Already identifeid and implemented applications of our devices range from noninvasive testing of semiconductor VLSI circuits to free-space quantum communications and quantum cryptography.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | We report our studies on the performance of new NbN ultrathin-film superconducting single-photon detectors (SSPDs). Our SSPDs exhibit experimentally measured quantum efficiencies from ~ 5% at wavelength λ = 1550 nm up to ~10% at λ = 405 nm, with exponential, activation-energy-type spectral sensitivity dependence in the 0.4-μm - 3-μm wavelength range. Using a variable optical delay setup, we have shown that our NbN SSPDs can resolve optical photons with a counting rate up to 10 GHz, presently limited by the read-out electronics. The measured device jitter was below 35 ps under optimum biasing conditions. The extremely high photon counting rate, together with relatively high (especially for λ > 1 μm) quantum efficiency, low jitter, and very low dark counts, make NbN SSPDs very promising for free-space communications and quantum cryptography. | We report our studies on the performance of new NbN ultrathin-film superconducting single-photon detectors (SSPDs). Our SSPDs exhibit experimentally measured quantum efficiencies from ~ 5% at wavelength λ = 1550 nm up to ~10% at λ = 405 nm, with exponential, activation-energy-type spectral sensitivity dependence in the 0.4-μm - 3-μm wavelength range. Using a variable optical delay setup, we have shown that our NbN SSPDs can resolve optical photons with a counting rate up to 10 GHz, presently limited by the read-out electronics. The measured device jitter was below 35 ps under optimum biasing conditions. The extremely high photon counting rate, together with relatively high (especially for λ > 1 μm) quantum efficiency, low jitter, and very low dark counts, make NbN SSPDs very promising for free-space communications and quantum cryptography. | eng_Latn | 7,677 |
The superiority of parabolic-index fibers over step-index fibers in delivering high-beam-quality light out of incoherently combined lasers is demonstrated numerically and experimentally. By utilizing the tapered fused bundle-combining approach and connecting it with delivery fiber, we point to an efficient, rugged, all-glass, integrated, and nearly brightness-preserving device that is capable of transmitting high-quality output beams. | The importance of average power scaling of fiber lasers (FL) is well known. However, power scaling is strongly limited by factors such as thermal load, and non-linear effects. An alternative path for reaching high powers utilizes the stimulated Raman scattering mechanism, and harnesses its power and brightness enhancement potential to reach high average power, high brightness FL. kW scale Raman FLs have been demonstrated, however they are in core-pumping configurations, meaning that they require an a-priori existing brighter kW laser that acts as their pump modules. There have been only a few publications of Raman FLs where the generated signal has a higher brightness than the pump source at levels of ≥100W, the highest, being at 250W. Here we report a strictly all-fiber clad pumped Raman FL with a CW power output of 800 W with a conversion efficiency of 80%. To the best of our knowledge this is the highest power and highest efficiency Raman FL demonstrated in any configuration allowing brightness enhancement (i.e clad pumped or graded index fiber, excluding step-index core pumped), thus being the first kW-class Raman FL with brightness enhancement. This result was achieved with a specially designed triple-clad fiber (TCF). The core was 25 μm, 0.065 NA, and the inner cladding was 45 μm 0.22NA. The choice of the small inner clad allows obtaining sufficient Raman gain without requiring too long a fiber, as well as being compatible with the waist size of the pump source fiber. In addition this diameter complies with the inner-clad/core ratio which prevents generation of a 2nd Stokes laser beam. Two fiber Bragg gratings at 1120 nm written onto the TCF, were employed as the oscillator’s reflectors. The cavity was pumped by a lower beam-quality source with an M2 of ~8 at 1070 nm. The Raman signal generated in the core, at the first Stokes wavelength of 1120 nm, showed an improved beam-quality in relation to the pump. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,678 |
We propose to combine multiple laser beams into a single diffraction-limited beam by beam self-focusing (collapse) in a Kerr medium. Beams with total power above critical are first combined in the near field and then propagated in the optical fiber/waveguide with Kerr nonlinearity. Random fluctuations during propagation eventually trigger a strong self-focusing event and produce a diffraction-limited beam carrying the critical power. | We obtain, for the first time, an analytic theory of the forward stimulated Brillouin scattering instability of a spatially and temporally incoherent laser beam, that controls the transition between statistical equilibrium and non-equilibrium (unstable) self-focusing regimes of beam propagation. The stability boundary may be used as a comprehensive guide for inertial confinement fusion designs. Well into the stable regime, an analytic expression for the angular diffusion coefficient is obtained, which provides an essential correction to a geometric optic approximation for beam propagation. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 7,679 |
In this paper, we demonstrate the implementation of a widely tunable microwave signal generator based on a dual-polarization fiber grating laser. The laser contains two strong, wavelength-matched Bragg gratings photoinscribed in an Er-doped fiber and emits two polarization modes when pumped with a 980 nm laser diode. By beating the two modes, a microwave signal with a signal-to-noise ratio over 60 dB can be obtained. For a free running laser the fluctuations in intensity and frequency of the microwave signal are ±1 dB and ±5 kHz, respectively, and the noise level is about -40 dBc/Hz at 1 kHz. The frequency can be continuously tuned from 1.8 to 15.1 GHz, by transversely loading the laser cavity and changing the intracavity birefringence by use of a piezoelectric transducer-based mechanical device. The measured response time rate of tuning is about 90 MHz/μs and the intensity fluctuation at different frequencies is less than ±1.5 dB. The frequency fluctuation under loading is controlled within 1 MHz by introducing an electrical feedback. | Dual-frequency fiber lasers (DFFL) are shown to provide high purity beat notes for microwave signal generation and distribution. We study the stabilization of the beat from DFB DFFLs by using optical frequency-shifted feedback loop containing an electro-optic modulator (EOM). As a proof-of-principle of the method efficiency, a stabilized beat note with a phase noise level of –104 dBc/Hz at 1 kHz from a 1 GHz carrier, and of –90 dBc/Hz at 1 kHz from a 10 GHz carrier, is demonstrated when the EOM is driven by a synthesizer. Furthermore, the scheme is extended to a self-referenced scheme: a hybrid opto-electronic oscillator is obtained when the delayed DFFL beat note itself drives the EOM. Low-frequency phase noise is reduced by about 20 dB. Applications are discussed. | Single-mode operation at 4.4 THz is obtained from distributed-feedback quantum-cascade lasers with complex-coupling metallic gratings. The emission shows a stable side-mode suppression of more than 20 dB at all injection currents and operating temperatures | eng_Latn | 7,680 |
A package for a DFB (distributed feedback) laser with integrated optical isolator is described. The design is based on a modular set-up: a laser module provided with a short ferruled pigtail is combined with an optical isolator module with the device fiber pigtail. Laser feedback due to reflections in the isolator module is avoided by slanting the collimated beam through the isolator. An advantage of the design is that both modules can be tested separately. Tests in a 2.5-Gb/s system show that proper data transmission is maintained over a 100-km fiber link despite a deliberately imposed back-reflection at a level of 10%. A bit error rate of 10/sup -10/ at 10% laser feedback is obtained for -31 dBm detector power. > | The multiplication of fibre optic networks during the years 1980 to 2000 has led to the development of specific packaging designs for laser modules, e.g. butterfly or TO-can coaxial packages. Since the beginning of years 2000, it has become necessary for packaging designers to deal with new requirements in term of module size, cost, thermal and electrical performances, particularly concerning the HF design. From these new requirements, new quasi-standards have appeared: TO-based TOSAs, XMD, and so on... However, these solutions are still based on traditional technologies : die soldering, 3D active alignment, Kovar packages, laser welding, single-chip devices, discrete micro-optics., unsuitable for mass production at very low cost. ::: Today, the challenge for optoelectronic industry is thus to achieve a mutation of the packaging and assembly concepts, similar to the one the microlelectronic industry has done thirty years ago, by introducing advanced packaging technologies in order to address emerging markets and need, such as FTTx and Very Short Reach optical links, at the targeted costs. This will be also done by pushing ahead the integration of several optical function on the same chip or optical board. ::: Some of these emerging technologies, such as optical MCM (Multi Chip Module), passive alignment, new materials for thermal management, flip-chip hybridisation, are key concepts to manage this next step and are reviewed in this paper. ::: These concepts have already been applied in some industrial products and should spread in the next years. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,681 |
Monolithic integration of InP-based materials on Si will allow lasers as well as optical amplifiers operating at 1.55µm to be efficiently included in photonic integrated circuits. We demonstrate here oxide-free heteroepitaxial bonding of InP-clad GaInAs quantum wells to Si, with an atomic-plane-thick reconstruction across the InP-Si interface. The wells photoluminescence emitted-wavelength demonstrates no shift after bonding. Several InP surface activation procedures have been investigated. This bonding approach is compatible with guiding designs including a nanostructuration, thus enabling specific designs associated to desirable optical functions. | An heteroepitaxial bonded III-Von Si nanopatterned waveguide is demonstrating a wavelength selective behavior thanks to a super-periodicity added to its sub-wavelength, below band-gap, structuration. Effective Medium Theory has been implemented for modal effective index determination, allowing a quick and nevertheless detailed investigation of the role of a large number of geometrical parameters. Such nanostructured waveguides offer the versatility for designing complex geometries required for hybrid advanced optical functions on silicon. | Background ::: Serum calcium (Ca) and inorganic phosphate (Pi) concentrations and calcium-phosphate product (CPP) levels are positively associated with worse outcomes in patients with chronic kidney disease, but there are few data for Pi or Ca and none for CPP in patients with chronic heart failure (CHF). | eng_Latn | 7,682 |
Optical networks are becoming a reality as the physical layer of high-performance telecommunication networks. The deployment of wavelength-division multiplexing (WDM) technology allows the extended exploitation of installed fibers now facing an increasing traffic capacity demand. Performances of such systems can be degraded by wide variations of the optical channel power following propagation in the network. Therefore a tilt control of optical amplifiers in WDM networks and dynamic channel power regulation and equalisation in cross-connected nodes is necessary. An important tool for the system designer is the variable optical attenuator (VOA). We present the design and the realization of newly developed VOAs using the ASOC technology. This technology refers to the fabrication of integrated optics components in silicon-on-insulator (SOI) material. The device is based on the light absorption by the free-carriers that are injected in the core of a rib waveguide from a p-i-n diode. The devices incorporate horizontally and vertically tapered waveguides for minimum fiber coupling loss. The p-i-n diode for carrier injection into the active region of the rib waveguide was optimised in order to enhance the attenuation. One major advantage of the ASOC technology is the possibility of monolithic integration of many integrated optics devices on one chip. In the light of this the paper illustrates the result of characterisation of multichannel VOAs. | A new type of Si guided‐wave electro‐optic modulator is proposed and analyzed. The modulator makes use of the impact‐ionization mechanism for carrier generation, and the carrier‐dispersion effect for electro‐optic conversion. Both electrical and wave propagation properties of the modulator were examined by a two‐dimensional device simulator and a three‐dimensional waveguide simulator, respectively. Numerical estimates of phase modulation due to refractive‐index change and intensity modulation due to optical absorption and radiation loss were obtained. One of important features of the prospected modulator is speed. The simulated turn‐on and turn‐off time of the modulator was less than 1 ns. GHz modulation is, therefore, possible for this class of modulators with device structure and doping profiles optimized for fiber coupling. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,683 |
We describe a microlaser longitudinally pumped by a laser diode with maximum 4W of cw power at 808 nm. Microlaser generates Q-switched laser pulses obtained by using a saturable absorber (Cr 4+ : YAG) in the laser resonator. Laser resonator is shorter than 20-mm. Pump radiation is focused with an opt ical collimation/focusing system. The optical-to- optical efficiency of the laser system is maximum when the dimensions of the pumped Nd: YAG rod volumes are dimensions comparable with those of the fundamental mode. Quasi- continuously pumped with 1.5W, the microlaser generates pulses with 13μJ energy, 2 ns pulse width, and 900 Hz, repetition rate, at 1064 nm wavelength. | Solid-State Laser Engineering is written from an industrialperspective and discusses in detail the characteristics, design, construction and practical problems of solid-statelasers. Emphasis is placed on engineering and practicalconsiderations, with a phenomenological treatment usingmodelsbeing preferred to abstract mathematical derivations.This new edition has been updated and revised to includeimportant developments, concepts and technologies that haveemerged since the publication of the first edition. | Efficient laser-diode pumped Cr, Yb:YAG self-Q-switched laser by bonding Yb:YAG crystal to enhance inversion population have been demonstrated for the first time. Average output power of 1 W and optical-to-optical efficiency of 18.5% have been achieved. | eng_Latn | 7,684 |
A terrestrial free-space optical communications network facility, named IN-orbit and Networked Optical ground stations ::: experimental Verification Advanced testbed (INNOVA) is introduced. Many demonstrations have been conducted to ::: verify the usability of sophisticated optical communications equipment in orbit. However, the influence of terrestrial ::: weather conditions remains as an issue to be solved. One potential solution is site diversity, where several ground ::: stations are used. In such systems, implementing direct high-speed optical communications links for transmission of data ::: from satellites to terrestrial sites requires that links can be established even in the presence of clouds and rain. NICT is ::: developing a terrestrial free-space optical communications network called INNOVA for future airborne and satellitebased ::: optical communications projects. Several ground stations and environmental monitoring stations around Japan are ::: being used to explore the site diversity concept. This paper describes the terrestrial free-space optical communications ::: network facility, the monitoring stations around Japan for free-space laser communications, and potential research at ::: NICT. | Our current and future Free Space Optical (FSO) designs and performance will be presented; Acquisition, Tracking, and Pointing (ATP) will be a key focus along with the size, weight and power (SWaP) of our existing ground systems and our design targets for space applications. Without gimbals, Rislet prisms, steering mirrors, or off-optical-z-axis sensing, and with only five static non-moving optical elements, we simply move an optical fiber in the focal plane to track the input and output beam angles over the entire wide range pointing field in both azimuth and elevation. Our optical design uses only five statically mounted elements. Fine pointing accuracies are sustained over the entire field without the use of coarse pointing and control systems. The impacts on SWaP are significant, and greatly simplify the packaging and ATP control systems. Our bi-directional ground-links have operated from 1 to 10 Gbps with link distances from 1 to 10 km. The primary ground systems that were delivered had ATP fields of 10o or 30o in both azimuth and elevation. For the 30o system, the pointing resolution is 470 nano-radian, while the 10o system provides 147 nano-radian pointing resolution. We also discuss the performance of our ground links and anticipated performance for various space applications. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,685 |
We experimentally investigate the dynamics of a three-section monolithically integrated semiconductor laser (MISL). The MISL is designed and fabricated by ourselves, which is composed of a distributed feedback (DFB) laser section, a phase (P) section and an amplifier (A) section with lengths of 220 µm, 240 µm, and 320 µm, respectively. Two types of intermittent chaos states named as TC1 and TC2 have been observed. For TC1, the intermittent behavior is characterized by the chaotic state interrupting the stable state. As for TC2, the intermittent behavior is characterized by the chaotic state interrupting the period two state. The evolution route of the dynamical state in the MISL is analyzed. | Influences of external optical injection on the nonlinear dynamics of a three-section monolithically integrated semiconductor laser (MISL) are investigated experimentally. The results show that, for the solitary three-section MISL, diversely dynamical states including the stable state as well as the so-called period-one, period-two, multi-period, and chaotic states can be observed through adjusting the currents of the gain section ( $I_{G}$ ) and the phase section ( $I_{P}$ ). However, the chaotic operation region of the solitary MISL in the parameter space of $I_{G}$ and $I_{P}$ is very small and found to exist when $21.28~\textrm {mA} mA and $31~\textrm {mA} mA. After introducing an external optical injection, the MISL originally operating at other dynamical states can always be driven into chaotic state under suitable injection strength and frequency detuning, and a relatively large $I_{G}$ will be helpful for obtaining broad and continuous chaotic regions in the parameter space of injection strength and frequency detuning. | Although field-collected recordings typically contain multiple simultaneously vocalizing birds of different species, acoustic species classification in this setting has received little study so far. This work formulates the problem of classifying the set of species present in an audio recording using the multi-instance multi-label (MIML) framework for machine learning, and proposes a MIML bag generator for audio, i.e., an algorithm which transforms an input audio signal into a bag-of-instances representation suitable for use with MIML classifiers. The proposed representation uses a 2D time-frequency segmentation of the audio signal, which can separate bird sounds that overlap in time. Experiments using audio data containing 13 species collected with unattended omnidirectional microphones in the H. J. Andrews Experimental Forest demonstrate that the proposed methods achieve high accuracy (96.1% true positives/negatives). Automated detection of bird species occurrence using MIML has many potential applications, particularly in long-term monitoring of remote sites, species distribution modeling, and conservation planning. | eng_Latn | 7,686 |
A multi-lamination micromixer for time resolved infrared spectroscopy, optimized by fluid simulations is characterized for different flow rates. Using four instead of two lamination layers yields a reduction of the diffusion length and decreases mixing time significantly. Measurement results prove the ultrafast mixing performance of this micromixer (<1 ms for aqueous solutions). This device operates in a wide range of flow rates without performance drop illustrated by the linear relation between the mixing time and the flow rate. A new custom chip holder provides easy chip handling and higher pressure durability. | X-ray Free-Electron Lasers (XFELs) offer a unique opportunity to study the structural dynamics of proteins on a femtosecond time-scale. To realize the full potential of XFEL sources for studying time-resolved biomolecular processes however, requires the optimization and development of devices that can both act as a trigger and a delivery mechanism for the system of interest. Here we present numerical simulations and actual devices exploring the conditions required for the development of successful mixing and injection devices for tracking the molecular dynamics of proteins in solution on micro to nanosecond timescales using XFELs. The mechanism for combining reagents employs a threefold combination of pico-liter volumes, lamination and serpentine mixing. Focusing and delivering the sample in solution is achieved using the Gas Dynamic Virtual Nozzle (GDVN), which was specifically developed to produce a micrometer diameter, in-vacuum liquid jet. We explore the influence of parameters such as flow rate and gas pressure on the mixing time and jet stability, and explore the formation of rapid homogeneously mixed jets for ‘mix-and-inject’ liquid scattering experiments at Synchrotron and XFEL facilities. | Perfect Quantum Cloning Machines (QCM) would allow to use quantum nonlocality for arbitrary fast signaling. However perfect QCM cannot exist. We derive a bound on the fidelity of QCM compatible with the no-signaling constraint. This bound equals the fidelity of the Bu\v{z}ek-Hillery QCM. | eng_Latn | 7,687 |
A method of finding the time dependent resistances and inductances in the discharges in pulsed gas lasers is described in this work. According to this method the waveforms of the laser circuit voltages are digitized and their first and second derivatives are calculated. These are substituted into the differential equations governing the behavior of the system and relationships among the resistances and inductances are formed for every time. Using relationships from a sequence of four very closed adjacent time instants and considering that during this short time interval the resistances and inductances are varied linearly, their values can be found for this particular time interval. Repeating the same procedure for other time intervals and scanning the entire time region of the discharge, the time histories of the resistances and inductances of the discharges are revealed. These show strong variations in the "formation phase" of the discharge (first 50 nsec). Specifically the resistances drop rapidly (first 10 nsec) from very high values to low values, while the inductances increase to high values and subsequently decrease, forming an abrupt high peak. The steep drop of the resistances is due to the electron avalanche multiplication, while the peak of the inductances is due to the centripetal magnetic forces (Laplace forces), which cause a temporary constriction of the plasma. In the "main phase" of the discharge the resistances present a damping oscillation with the same frequency as the voltages, while the inductances present light fluctuations around constant values. > | A new method of finding the time histories of the resistance and inductance of a discharge in the laser chamber of a pulsed gas laser is described. This method exploits simultaneously the voltage across the laser channel and the flowing current in the laser discharge while the knowledge of the entire circuit is not required. The mathematical model used is simple and the results show strong variations of the resistance and inductance during the formation phase of the discharge while in the main phase these quantities fluctuate around constant values. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,688 |
The design, construction, and operation of a stratospheric Rayleigh lidar system is outlined. The lidar system was designed to operate as a Doppler lidar; however, for the first stage of the project it was set up to operate in a manner similar to a more conventional stratospheric Rayleigh lidar. This system includes a number of unique design features, including a high-pulse-repetition-frequency laser and the use of a single 1-m-diameter telescope for transmission of the laser pulse and reception of the backscattered light. An associated high-speed rotating shutter system switches the optical system from the transmission to the reception mode. The system was operated at Adelaide, Australia (35° S, 138° E). Scattering ratio and temperature profiles are calculated for data collected during the period from 10 March 1992 to 11 May 1993. The scattering ratio profiles clearly show the reduction in the scattering from the stratospheric aerosol layer. This is due to the removal of the aerosol injected by the eruption of Mt. Pinatubo. The measured relative density profiles show very good agreement with the Cospar international reference atmosphere model densities, as do the temperature profiles calculated from these. | The main working mode of high energy laser system is to focus the transmitting laser beam on target under the condition that the target is tracked in closed loop by fine tracking module, so that it can be damaged or invalidated. Therefore, in order to achieve this effect, an optical device of common aperture is designed for high energy laser system. The emitting system of this device consists of an off-axis two-trans primary telescope module, a Galileo transmission telescope module used in focusing and a beam feeding module composed of dichroic mirror, fast mirror and other optical elements; at the same time, the receiving system of this device consists of the same off-axis two-trans primary telescope module, an imaging module used in fine tracking and the same beam feeding module. Taking incoherent combination laser in space as incident ray, we use optical design software in both sequential mode and non-sequential mode to design and simulate this device. The simulation results show that the distribution of spot at 0.5km~5km is obtained after the laser is modulated by different focusing quantities in the focusing telescope module, and the RMS value of laser wave front is better than λ/20 for emitting system. In addition, the performance of an imaging optical system composed of the primary telescope module and the fine tracking imaging module approach the diffraction limit after optimizing, and the system transfer function is greater than 0.6 at 70lp/mm. Such results in this paper confirm that the structure of this optical transceiver possesses reasonable structure and reliable performance, which meets the requirements of engineering application for high energy laser system. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 7,689 |
We report a novel optoacoustic (OA) cell construction which has improved small absorption measurement capability from 10−9 cm−1 to 10−10 cm−1. The new OA cell is ideally suitable for use with planar output lasers, e.g., diode lasers. Now optoacoustic spectroscopy can be extended to include the effects of low temperatures, electric fields, and magnetic field effects. | An improved spectrophone for measurements of laser absorption in gases has been tested. The device employs a fiber-optic interferometer, wound into a cylindrical shape, as the acoustic sensor. Performance of the device was evaluated by measuring the absorption of 3.39 μm HeNe laser radiation in a calibrated mixture of methane in Argon. Results indicate a minimum detectable absorption capability of 2x10-7cm-1 W/√ MHz , although a background signal 30 dBV above the noise limited performance. We report an improvement in sensitivity several orders of magnitude above the first fiber-optic spectrophone.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,690 |
Er doped III-nitride semiconductors are a major field of research aiming to achieve photonic devices with multiple functionalities in photonic integrated circuits (PICs), which are not possible with either Er doped silica glasses or narrow band gap semiconductors like InGaAsP. Emitters and optical amplifiers based on Er doped GaN/InGaN operating at 1.54 μm are expected to be electrically pumped, integratable, temperature insensitive and have high signal gain with low noise. These properties are very attractive for next generation optical network systems where multiple amplification steps are required. We will discuss here the metal organic chemical vapor deposition (MOCVD) growth of Er doped GaN/InGaN epilayers. Further, we report on the fabrication of chip size current injected 1.54 μm emitters and optical amplifiers by heterogeneously integrating MOCVD grown Er doped GaN/InGaN with 365 nm nitride light-emitting diodes. The emitted intensity at 1.54 μm varied almost linearly with input forward current. The feasibility of electrically pumped optical amplifiers for PICs with the advantages of both semiconductor optical amplifiers and Er-doped fiber amplifiers will also be discussed. | The authors report on the excitation dynamics of the photoluminescence (PL) emission of Er doped GaN thin films synthesized by metal organic chemical vapor deposition. Using the frequency tripled output from a Ti:sapphire laser, the authors obtained PL spectra covering the ultraviolet (UV) to the infrared regions. In the UV, a dominant band edge emission at 3.23eV was observed at room temperature; this is redshifted by 0.19eV from the band edge emission of undoped GaN. An activation energy of 191meV was obtained from the thermal quenching of the integrated intensity of the 1.54μm emission line. This value coincides with the redshift of the band edge emission and is assigned to the ErGa-VN complex level. | Background ::: Serum calcium (Ca) and inorganic phosphate (Pi) concentrations and calcium-phosphate product (CPP) levels are positively associated with worse outcomes in patients with chronic kidney disease, but there are few data for Pi or Ca and none for CPP in patients with chronic heart failure (CHF). | eng_Latn | 7,691 |
DWDM transport networks are evolving towards dynamic setup/rerouting of optical connections. This paper quantifies the impact of optical node architecture and traffic variability on the network blocking probability and transponder count requirements. | This paper presents a synopsis of ongoing research in the field of resource allocation in dynamic optical networks. This type of networks are envisioned to serve connections with random arrival and holding times and with fast connection setup requirements. Based on this, we model resource allocation as a mechanism that includes network control functions for routing and spectrum assignment (RSA), connection admission control (CAC) and grade of service (GoS) control. The goal is to efficiently assign spectrum resources to connections so as to attain optimum performance. For that, the network is modelled as a stochastic loss system subject to spectrum continuity and contiguity constraints. The theory of Markov decision processes (MDP) is then applied to formulate an algorithm that performs fast, adaptive and state-dependent RSA, CAC and GoS control. The proposed algorithm can easily be integrated with existing protocols for fast connection setup. Moreover, we discuss the cost efficiency of selected network implementations which are based on basic, colorless and colorless and directionless optical nodes. | Coherent optical OFDM systems offer a straight-forward approach to address high spectral efficiency. Non-linear impairments set limits to the maximum spectral efficiency. The limiting effects are explored by simulations, calibrated from published experimental results. | eng_Latn | 7,692 |
Volumetric thermal gratings were created in liquid and gaseous media and were used to efficiently deflect laser beams. In gaseous media, a low-input energy requirement and high switching efficiency make this type of switch a good candidate for a practical device. The switch is scalable to large apertures and has low insertion loss. | The beam propagation method (BPM) was used to study a 4/spl times/4 active switch with electro-optical effects in a titanium diffused lithium niobate (LiNbO/sub 3/:Ti) based directional coupler, and the results were used to develop the design. This design is capable of de-multiplexing wavelengths from two groups, 1100 nm to 1300 nm and 1500 nm to 1600 nm. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,693 |
The effective simulation technique of multipath interference in optical line consisting of different types of single-mode fibers, such as dispersion management lines, is proposed. The proposed technique also valid for analysis multipath interference in optical lines with distributed Raman amplification. The simulation technique is validated by comparison with exact solutions for lines without and with distributed Raman amplifier.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. | We discuss the importance of distributed amplification for high-speed soliton communication systems through numerical simulations by considering the distributed gain provided by stimulated Raman scattering or erbium dopants. Hybrid amplification schemes are also considered. At a bit rate of 40 Gb/s, the use of distributed amplification is found to improve the transmission distance (deduced from the Q parameter) by a factor of up to three for Raman amplification and >5 for erbium dopants, compared with the case of lumped amplifiers. The increase in transmission distance is by a factor of about two for 80-Gb/s soliton systems when dense dispersion management is used. | A combined Raman elastic-backscatter lidar has been developed. A XeCl excimer laser is used as the radiation source. Inelastic Raman backscatter signals are spectrally separated from the elastic signal with a filter or grating polychromator. Raman channels can be chosen to register signals from CO2, O2, N2, and H2O. Algorithms for the calculation of the water-vapor mixing ratio from the Raman signals and the particle extinction and backscatter coefficients from both elastic and inelastic backscatter signals are given. Nighttime measurements of the vertical humidity distribution up to the tropopause and of particle extinction, backscatter, and lidar ratio profiles in the boundary layer, in high-altitude water and ice clouds, and in the stratospheric aerosol layer are presented. Daytime boundary-layer measurements of moisture and particle extinction are made possible by the improved daylight suppression of the grating polychromator. Test measurements of the CO2 mixing ratio indicate the problems for the Raman lidar technique in monitoring other trace gases than water vapor. | eng_Latn | 7,694 |
In this paper the performance of a digital quadrature PWM modulator for switched-mode wideband transmitters is evaluated. The purpose of the evaluation is to analyze the impact of the modulator parameter settings on the signal band quantization noise and on the average power efficiency of the complete digital transmitter. Considering a realistic setup at GHz range, the performance conditions for an accurate operation are studied as well. According to the results a higher average transmitter efficiency can be expected for a 10 MHz LTE signal excitation when compared with a similar modulator structure utilizing ΣΔ modulation. | Single-ended (monopolar) and push-pull (bipolar) power amplifiers (PAs) are based upon complementary class-D PAs. The radio-frequency pulse-width modulation (RFPWM) waveform is produced in software and downloaded to a programmable-waveform generator. The PAs operate at 500 kHz and produce peak outputs of 100 W (monopolar) and 187 W (bipolar) with 85-percent efficiency. These amplifiers exhibit excellent linearity; IM products for single-tone AM and two-tone signals are about 40 dB below the desired sidebands. High efficiency is maintained over a dynamic range of 13 to 15 dB. This results in average efficiencies of 84 percent for signals with peak-to-average ratios up to 6 dB and 80 percent for a peak-to-average ratio of 10 dB. RFPWM also produces a clean output spectrum in which the spurious products are well removed from the desired signal. | We report nearly complete preservation of “spin memory” between optical absorption and photoluminescence under excitation >0.2 eV above the band gap in nanometer GaSe slabs. | eng_Latn | 7,695 |
A whispering gallery mode (WGM) semiconductor laser with a convex disk cavity operating at room temperature in the middle-IR range (λ = 2.4 μm) has been created for the first time. The convex cavity was formed by etching in a specially selected CrO3-HF-H2O mixture. The room-temperature emission spectra have been measured. The laser generates WGMs at room temperature in a pulsed regime. | We report the first demonstration of a cw room-temperature mid-IR microlaser. This 2.7-μm optically-pumped (diode, 980 nm) microlaser is based on a high-Q Er-doped ZBLAN spherical microresonator and has a threshold power of 140 μW. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,696 |
A novel mode-selective optical packet switching, based on mode-multiplexers/demultiplexers and multi-port optical micro-electro-mechanical systems (MEMS) switches, has been proposed and experimentally demonstrated. The experimental demonstration was performed using the LP(01), LP(11a) and LP(11b) modes of a 30-km long mode-division multiplexed few-mode fiber link, utilizing 40 Gb/s, 16-QAM signals. | Mode-division multiplexing (MDM), which allows different guided modes of a few-mode fiber to carry different signals, is a new technology being actively pursued worldwide to increase the signal-carrying capacity of a fiber. For the development of the MDM technology, many mode-controlling devices are needed, such as mode converters, mode (de)multiplexers, mode filters, and mode-selective switches. Among the various technologies available for the implementation of such devices, the polymer waveguide technology offers many distinct advantages. This paper presents a review of polymer waveguide devices for MDM applications, which include grating-based mode converters, 3D mode (de)multiplexers, graphene-based mode filters, and thermo-optic mode-selective switches. | MEMS technology offers some unique product opportunities for optical networking applications. One of the critical factors that determine the commercial success of any optical MEMS components is the cost for packaging and optical fiber alignment. Small form factor MEMS components such as protection switches and variable optical attenuators require the integration of optical fibers and lenses with the MEMS silicon chip itself. This work uses a MEMS 2 × 2 optical switch as a test vehicle to demonstrate a fiber optic lens design, specifically engineered for use with the micromachined silicon chip, that enables the use of passive fiber optic lens alignment to significantly reduce component assembly cost. | eng_Latn | 7,697 |
We demonstrate the tunable continuous-wave (CW) terahertz generator based on the λ/4 phase-shifted 1.3 μm dual-mode laser diode (DML) and travelling-wave photodiode (TWPD). The DML and TWPD operate as an optical beat source and terahertz photomixer, respectively. The laser diodes (LDs) operating at the 1.3 μm have more suitable characteristics as optical beat sources than the LDs operating at 1.55 μm because of their high efficiency and better thermal stability. The micro-heaters are integrated on top of each DFB LD for mode beat frequency tuning. The fabricated DML was continuously tuned from 230 GHz to 1485 GHz by increasing the temperature of each DFB section independently via integrated micro-heaters. The high-speed TWPD with an InGaAs absorber was designed and fabricated to efficiently generate the photomixing terahertz CW. A complementary log-periodic antenna was integrated with the TWPD to radiate the generated terahertz wave with minimum reflection in the wide frequency range. The terahertz characteristics of the tunable CW terahertz generator based on the DML and TWPD were measured in a fiber-coupled, homodyne terahertz photomixing system. Our results of the tunable CW terahertz generator show the feasibility of a compact and highly efficient CW terahertz spectrometer and imager. | Phase correlation leading to self-pulsation (SP) in semiconductor distributed Bragg reflector (DBR) lasers is investigated experimentally and theoretically. Under proper biasing conditions, the laser oscillates with three main modes and we observe that each two-modes beating provides SP with identical spectral linewidth. Under the same operating conditions, the measured spectral linewidths of the beating modes are much larger than the linewidth of the self-pulsating signal. These results demonstrate the natural occurrence of passive mode-locking (PML) and phase correlation in semiconductor DBR lasers. A model based on multimode coupled-wave rate equations, including four-wave mixing (FWM), is developed to describe PML and SP in the gain region of the laser cavity. This model demonstrates that the existence of phase correlation between longitudinal modes is due to FWM. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,698 |
Spectral properties of silicon subwavelength grating waveguides are simulated in 3D with eigenmode expansion and the impact of the number of included modes is investigated. Simulation results are validated against measurements. | While current optical communication networks efficiently carry and process huge amounts of digital information over large and medium distances, silicon photonics technology has the capacity to meet the ceaselessly increasing demand for bandwidth via energy efficient, inexpensive and mass producible short range optical interconnects. In this context, handling electrical-to-optical data conversion through compact and high speed electro-optical modulators is of paramount importance. To tackle these challenges, we combine the attractive properties of slow light propagation in a nanostructured periodic waveguide together with a high speed semiconductor pn diode, and demonstrate a highly efficient and mass manufacturable 500 µm-long silicon electro-optical device, exhibiting error free modulation up to 20 Gbit/s. These results, supported by modulation rate capabilities reaching 40 Gbit/s, pave a foreseeable way towards dense, low power and ultra fast integrated networks-on-chip for future chip-scale high performance computing systems. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 7,699 |
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