Synthesis and reconstruction of computer generated holograms by a double pass technique on a twisted nematic-based liquid crystal spatial light modulator

Achieving phase only modulation from a spatial light modulator (SLM) is useful for many optical processing tasks. In this paper, we demonstrate a simple method of decoupling phase and amplitude modulation in a twisted nematic liquid crystal (TNLC) SLM using a double pass technique. A Jones calculus model is developed which matches our experimental data.     

干涉测量用半导体激光器驱动电源

设计了一种可调制的高稳定度半导体激光器驱动电路。该电路的直流稳定度高达1.5×10-5，输出电流在0～200mA内连续可调，长时间工作（12h以上）电流变化小于1μA；在直流基础上注入100kHz～300kHz的调制电流，其调制深度为0～100mA连续可调，可实现在激光干涉测量中对光波频率和光波强度的调制。将该电路驱动的光栅外腔半导体激光器和辅助温度控制电路应用于光干涉测量技术中，得到了功率稳定、波长单一的激光输出，解决了激光器的跳模现象，完成了对远距离微小振动（纳米量级）的测量。     

自启动的非归零/归零码和光电时钟信号发生器及码型转换

采用双波长注入一包含伪随机码发生器与相位调制器的光电振荡器可以同时得到非归零(NRZ)码,归零(RZ)码以及光,电时钟信号输出。该方案使用了光域耦合的双环路结构,在不增加有源器件的条件下实现边模抑制。相位调制器用于反馈调制并同时实现占空比可调的非归零码到归零码的转换。双波长的注入排除了编码信号在振荡器中引入的非时钟频率成分。实验给出了10 Gb/s工作速率下的结果,得到了抖动为637 fs的光信号输出。转换得到的归零码信号占空比约为33%。输出电时钟信号的相位噪声在频偏10 kHz处为-109 dBc/Hz,边模抑制比为58 dB。     

可调谐二极管激光吸收光谱法测量气体温度

研究了一种新型的非接触式测温技术——可调谐二极管激光吸收光谱(TDLAS)测温技术。介绍了温度测量及调制吸收光谱技术原理,分析了调制幅度对气体温度测量的影响。优选了氧气吸收谱线对13163.78 cm-1和13164.18 cm-1,在搭建的高温实验系统上,实现了气体温度和浓度的同时测量。通过分析实测波形获得了谱线13164.18 cm-1在823~1323 K温度范围内的碰撞展宽系数和温度指数。实验结果表明,在823~1323 K温度范围内,系统温度测量的线性误差为0.65%,最大波动为±15 K。     

利用法布里-珀罗腔抑制电光相位调制中的剩余幅度调制

激光经电光相位调制后,由于剩余幅度调制的存在造成调制边带幅度不相等。利用法布里-珀罗腔的透射特性和Pound-Drever-Hall技术对通过法布里-珀罗腔的调制光正、负一级边带的幅度产生不同的衰减,使得调制边带的幅度相等,从而实现对电光相位调制中剩余幅度调制的抑制。采用该方法,理论上计算了调制光经法布里-珀罗腔后的光外差光谱信号,获得锁定法布里-珀罗腔后调制边带幅度的不对称度较腔锁定前减小四个数量级。实验研究了调制光经法布里-珀罗腔透射的光外差光谱,结果表明将法布里-珀罗腔锁定于该透射光外差光谱中心零位时,对剩余幅度调制的抑制程度可达45 dB。     

基于振幅调制的超冷铯原子高分辨光缔合光谱的实验研究

基于振幅调制的超冷铯原子高分辨光谱的实验研究，用相对于铯分子6S_1/2+6P_3/2离解限红失谐的光缔合激光作用于磁光阱中超冷铯原子，观察到通过光缔合产生的激发态超冷分子.在实验中，为了得到高信号-噪声比的光缔合光谱，利用声光调制器对俘获光进行振幅调制，将探测到的超冷铯原子的荧光信号利用lock-in技术解调.同时利用密度矩阵方程系统地分析了实验结果.     

Steepest-descent method-based adaptive frequency domain equalizer in coherent optical orthogonal frequency division multiplexing with quadrature phase shift keying modulation

An adaptive frequency domain equalizer (A-FDE) in quadrature phase shift keying-coherent optical-orthogonal frequency division multiplexing (QPSK-CO-OFDM) system is proposed in this paper. A-FDE uses steepest descent method to search the optimal equalization parameters. And through applying the adaptive control factor (ACF) to monitor the state of A-FDE, the interference from phase noise (PN) and chromatic dispersion (CD) can be mitigated. The numerical simulation shows that the performance of A-FDE has a remarkable improvement on combating PN and CD comparing with the conventional decision-directed equalizer (DDE). And the A-FDE can achieve the forward-error-correction (FEC) threshold in noisier scenario. Furthermore, because the calculation of ACF only bases on valid data instead of pilot symbols (PSs), A-FDE has low PS overhead merit.     

On intensities of perturbed random measures on Hausdorff spaces

Abstract

This article studies classes of random measures on topological spaces perturbed by stochastic processes (a.k.a. modulated random measures). We render a rigorous construction of the stochastic integral of functions of two variables and showed that such an integral is a random measure. We establish a new Campbell-type formula that, along with a rigorous construction of modulation, leads to the intensity of a modulated random measure. Mathematical formalism of integral-driven random measures and their stochastic intensities find numerous applications in stochastic models, physics, astrophysics, and finance that we discuss throughout the article.     

Broadening-independent demodulation for wavelength modulation spectroscopy based on even-order harmonics

The line broadening of gas absorption spectrum is a significant but unknown factor in traditional demodulation of wavelength modulation spectroscopy, which is a kind of tunable diode laser absorption spectroscopy in weak absorption cases. In this paper, another signal demodulation method based on some simple algebraic operations with the amplitudes of the zero-, second-, and fourth-order harmonics was proposed. With this method the effect of spectrum broadening could be selfeliminated. That makes the amplitude of the demodulated signal is irrelevant to the broadening, and enables the direct and fast measurement without complex simulations and curve fittings in traditional method.     

Intermodulation of transverse magnetoresistance oscillations in structures with strong intersubband interaction

In the Shubnikov–de Haas oscillation spectrum of doped InAs/AlSb structures, high-amplitude peaks are established at combination frequencies. It is demonstrated that they are caused by a significant contribution of intersubband scattering to the processes of electron-electron interaction. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 32–38, December, 2008.