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41.
Supradeepa V. R. Long C. M. Leaird D. E. Weiner A. M. 《Photonics Technology Letters, IEEE》2010,22(3):155-157
42.
Weiner J.S. Lee J.S. Leven A. Baeyens Y. Houtsma V. Georgiou G. Yang Yang Frackoviak J. Tate A. Reyes R. Kopf R.F. Wei-Jer Sung Weimann N.G. Young-Kai Chen 《Solid-State Circuits, IEEE Journal of》2004,39(10):1720-1723
Return-to-zero differential phase-shift keying applications require a differential amplifier with high bandwidth, high gain, low noise, and good input impedance match. In this paper, we describe an InGaAs-InP heterostructure bipolar transistor differential transimpedance amplifier with high bandwidth of 47 GHz and high gain of 56 dB-/spl Omega/. The input-referred current noise is less than 35 pA//spl radic/Hz over the measurement range up to 40 GHz. 相似文献
43.
We report transmission of ~60-fs and ~245-fs pulses, respectively, over 42-m and 2.5-km fiber links which consist of standard single-mode fibers (SMF) concatenated with dispersion-compensating fibers (DCF). The experiments using very short pulses (~60 fs) over a short fiber length (~42 m) demonstrate the ability to achieve simultaneous dispersion and dispersion slope compensation using this technique. Femtosecond spectral interferometry measurements of this 42-m link show that its residual dispersion slope is approximately six times lower than that of the dispersion-shifted fiber. Finally, to demonstrate that the dispersion-limited propagation distance is proportional to the cube of the pulsewidth, we transmit ~245-fs pulses over a 2.5-km SMF-DCF link and achieve comparable pulse restoration as with the shorter fiber experiments 相似文献
44.
Programmable shaping of femtosecond optical pulses by use of128-element liquid crystal phase modulator 总被引:3,自引:0,他引:3
Weiner A.M. Leaird D.E. Patel J.S. Wullert J.R. II 《Quantum Electronics, IEEE Journal of》1992,28(4):908-920
Programmable shaping of femtosecond pulses by using a 128-element liquid crystal modulator to manipulate the phases of optical frequency components which are spatially dispersed within a grating-and-lens pulse shaping apparatus is described. This apparatus makes possible gray-level control of the spectral phases and allows modification of the pulse shape on a millisecond time scale under electronic control. Refinements in the design of the multielement modulator result in pulse shaping fidelity comparable to that which can be achieved with microlithographically fabricated masks. Several examples of pulse shaping operation, including pulse position modulation, programmable pulse compression, and adjustable cubic phase distortion, are described 相似文献
45.
George Seibel Peter Kollman Scott Weiner U.Chandra Singh 《Telematics and Informatics》1985,2(4):307-310
Improving the understanding of complex molecular systems is an important and interesting use of supercomputers. Computer simulation currently plays, and will continue to play, a vital role in research in this area by acting as a guide to site-specific mutagenesis. This study explains simulations of complex molecules. 相似文献
46.
Brubaker R.M. Yi Ding Nolte D.D. Melloch M.R. Weiner A.M. 《Quantum Electronics, IEEE Journal of》1997,33(12):2150-2158
The diffraction of 100-fs pulses from the static gratings of photorefractive quantum wells (QWs) produces diffracted pulses that are nearly transform-limited, despite the strong dispersion near the quantum-confined excitonic transitions. This quality makes the QW's candidates for use in femtosecond pulse shaping, although the currently limited bandwidth of the quantum-confined excitonic transitions broadens the diffracted pulses. Femtosecond electric-field cross correlation and spectral interferometry techniques completely characterize the low-intensity pulses diffracted from stand-alone photorefractive QWs, and from QWs placed inside a Fourier-domain femtosecond pulse shaper 相似文献
47.
We demonstrate full characterization of femtosecond pulse distortion induced by all-order polarization mode dispersion (PMD) at selected polarization states via second-harmonic generation (SHG) frequency-resolved optical gating (FROG) measurements at an average power of under 28 nW. By applying the inverse of the measured spectral phase via a programmable pulse shaper, we compress the distorted pulses from more than 3 ps to nearly bandwidth-limited durations of less than 500 fs. Our results show that SHG FROG measurements performed by using fiber-pigtailed aperiodically poled lithium niobate waveguides can serve as a robust and sensitive tool for characterization of PMD-induced spectral phase. 相似文献
48.
In this survey recent results about q-analogues of some classical theorems in extremal set theory are collected. They are related to determining the chromatic number of the q-analogues of Kneser graphs. For the proof one needs results on the number of 0-secant subspaces of point sets, so in the second part of the paper recent results on the structure of point sets having few 0-secant subspaces are discussed. Our attention is focussed on the planar case, where various stability results are given. 相似文献
49.
We report a structural characterization using X-ray absorption spectroscopy of the molybdenum site of Escherichia coli YedY, a novel oxidoreductase related to be the sulfite oxidase family of molybdenum enzymes. We find that the enzyme can exist in Mo(V) and Mo(IV) oxidation states but cannot be readily oxidized to the Mo(VI) form. Mo(V) YedY has molybdenum coordination similar to that of sulfite oxidase, with one Mo═O at 1.71 ?, three Mo-S at 2.39 ?, and one Mo-OH at 2.09 ?, which elongates to 2.20 ? upon reduction to Mo(IV), indicating Mo-OH(2) coordination. The Mo(V) enzyme also possesses a long Mo-O coordination at 2.64 ?, which may be due to oxygen coordination by Asn-45 O(δ), with Mo-O(δ) approximately trans to the Mo═O group. A comparison with sulfite oxidase indicates that YedY possesses a much more uniform Mo-S coordination, with a maximum permitted deviation of less than 0.05 ?. Our results indicate that the YedY active site shows considerable similarity to but also important differences from that of reduced forms of sulfite oxidase. 相似文献
50.
A dispersion law for virtually imaged phased-array spectral dispersers based on paraxial wave theory
We derive the spectral dispersion law for the virtually imaged phased array (VIPA) based on paraxial wave theory using the Fresnel diffraction analysis. The validity of the dispersion law is verified by comparison with experiments. This spectral dispersion law is compared to a previous law based on plane wave theory. At small incident angles where the VIPA provides its largest spectral dispersion, the paraxial wave law provides a much better fit to the data than the plane wave law does. 相似文献