双区共腔双稳态激光器电注入下特性的计算机模拟

本文对双区共腔半导体双稳态激光器在电注入下的稳态及瞬态特性进行了计算机模拟,这种模型产生双稳和自脉动现象的机制是不均匀电注入本征可饱和吸收特性,我们研究了与可饱和吸收有关的几个参数r、ξ、J_1、J_2对双稳及自脉动现象的影响.     

半导体DH条形激光器的瞬态稳定性与稳态稳定性的关系

从实验上研究了GaAs-Al_xGa_(1-x)AsDH条形激光器的稳态束腰、束宽和激光功率随电流变化的规律与瞬态自脉动的关系。随着稳态注入电流的变化,激光器的垂直束腰位置都在镜面上,其束宽不变;不管水平束腰位置是否有变化,水平束腰宽有明显变化时,其瞬态往往出现自脉动,而出现自脉动的电流范围往往在光功率特性的A、B扭折之间。     

量子点激光器瞬态响应及调制特性分析

基于二能级系统建立量子点激光器的载流子-光子速率方程模型,分析量子点激光器的瞬态响应和调制特性,获得其动态特性.同时分析了注入电流对量子点激光器输出光子密度的影响,随着注入电流的增大,激光器光电延迟时间缩短,弛豫过程缩短,弛豫振荡频率增大,且输出光子峰值和稳态功率增加,适当增加注入电流可拓宽量子点激光器调制带宽.通过小信号调制分析,发现量子点激光器上限调制频率比普通激光器高一个数量级,证明了其具有良好的高频调制特性.     

注入锁定半导体激光器调制特性研究

通过速率方程建立外光注入半导体激光器的理论模型,在注入锁定条件下对其进行稳态及小信号分析,研究了注入光对调制特性的影响.结果表明,强光注入在一定程度上增大了谐振频率和调制带宽,但是抑制了响应增益,通过增大偏置电流加以补偿,才能获得理想的响应增益和带宽;并且外光注入大大降低了低频调制时的频率啁啾.     

主动镜结构Yb∶YAG激光器的热效应研究

以主动镜背冷结构Yb∶YAG为研究对象,借助有限元分析软件,并根据Yb∶YAG的三能级结构特点,系统分析比较了不同泵浦光特性和冷却条件下激光晶体内部稳态和瞬态下的温度及应力分布。分析结果表明,泵浦光的均匀性对激光晶体内部的温度梯度有较大影响,此外,同等泵浦和冷却条件下,瞬态下的温度梯度峰值大于稳态下的温度梯度峰值。分析结果对于固体激光器的设计有一定的借鉴作用。     

条型DH半导体激光器的稳态模型

通过对条型DH激光器光与物质相互作用的分析,建立了稳态模型。利用数值计算法得到了稳态解,用以说明激光器的电光特性曲线的非线性,以及近场漂移、远场变化及激射波长与注入电流的关系。     

共腔双区(CCTS)DH激光器的研究

本文综合报导对AIGaAs/GaAs、InGaAsP/InP共腔双区(CCTS)DH激光器的研究,结果表明CCTS激光器具有稳态和瞬态多功能特性,作为三端器件通过工作状态的选择可以控制激光器的“开”,“关”动作,和改善输出线性度,还可以控制产生微波调制光脉冲序列,尤其是具有模式稳定的光输出双稳态特性。文中对上述现象作了物理解释和半定量的理论分析。     

半导体双稳态激光器在光注入下的实验研究

本文报道了InGaAsP/InP 双区共腔脊形波导双稳激光器在外光注入下产生光-光双稳特性及光-光放大的实验结果,给出了器件在直流及脉冲工作时的光-光双稳特性,并对结果进行了初步分析.     

单腔双接触结构激光器双稳特性研究

本文从多纵模速率方程出发,在取定考虑有K选择的抛物带间吸收,增益系数的基础上,采用数值方法,对单腔双接触结构激光器的双稳特性的产生机理,以及影响它的两个最主要参数(即双稳区注入宽度和开关时间)的各种因素作了系统的分析. 稳态分析结果表明多纵模的工作状态将使双稳区注入宽度减少,而减少吸收区电注入或增大吸收区体积等可使双稳区注入宽度增大.瞬态分析结果表明,双稳开关过程可分为两个阶段,第一阶段谱宽大并伴有大幅度跳模;第二阶段占时较长,对双稳开关时间有较大影响,可通过加大增益区电注入来减少振荡衰减时间. 本工作为设计双稳器件,提高器件性能提供了基础.     

单端耦合QD-SOA波长转换特性研究

通过光场传输方程和电子跃迁速率方程,采用细化分段方法,解常微分方程组的四阶龙格-库塔法和求解非线性方程组的牛顿法,建立了针对动态输入信号的仿真模型。对基于单端耦合QD-SOA的交叉增益调制(XGM)波长转换器转换光增益、啁啾特性与有源区长度、输入光信号功率、注入电流之间的关系进行了研究。结果表明增大泵浦光、减小探测光、增大注入电流都可以增加转换光啁啾特性,通过增加有源区长度和后端面反射率可以有效提高转换光增益,而光增益随注入电流变化不大。     

Gain Control of Semiconductor Optical Amplifier Using a Bandpass Filter in a Feedback Loop

The authors present a simple configuration of a gain-clamped semiconductor optical amplifier (GC-SOA) based on automatic intensity control of a feedback light generated by amplified spontaneous emission, using a narrow bandwidth thin-film-tunable filter. Experimental results show that the proposed amplifier has good gain clamping characteristics and the feedback light dramatically reduces steady and transient gain variations. The feedback light operates satisfactorily with the channel's add-drop frequency up to 20.9 kHz. We also examined the performance of the GC-SOA by employing the feedback light at different wavelengths.     

Optimization of a-Si:H-based three-terminal three-color detectors

Three-terminal three-color n-SiC:H/a-Si:H-based TCO/PINIP/TCO/PIN/metal detectors are presented. Assemblies having different surface roughness of transparent conducting oxide (TCO) layers are compared with regard to the external steady-state characteristics and transient behavior. The roughness of the sputtered TCO surface can be modified by an etching treatment. With the selection of smooth or textured TCO surfaces, the wave propagation of light within the device is controlled. This design technique can be exploited to optimize the color separation and improve the reproducibility of spectral responsivities in the assemblies. The examined assemblies exhibit very selective spectral responsivity for the fundamental chromatic components (red-green-blue) and a linear photocurrent-generation rate relationship over more than five orders of magnitude of illumination intensity. Since the color detection of blue and green light is performed in the PINIP structure by bias switching, the transient current response of the PINIP structures is investigated. A reciprocal relationship between the delay time and illumination intensity is established. An optimum operation region for the switching voltages is determined with regard to the quality of color separation, dynamic range, and transient behavior     

A Paper-Based Wearable Photodetector for Simultaneous UV Intensity and Dosage Measurement

Photodetectors, which convert the light signal into other forms of signal, have been under the spotlight of research for many years because they are widely applied in monitoring, communication, and imaging. Most of the currently available photodetectors can output electrical signals to indicate the transient light intensity, while some display color change to reveal the absorbed light dosage. However, there is no device that can tell the transient light intensity and accumulated light dosage at the same time. Here, a paper-based wearable photodetector that can simultaneously measure transient light intensity and accumulated light dosage is reported. The phosphomolybdic acid/citric acid system, whose color change can be observed by the naked eye, is designed as the photochromic material to combine with photodetective materials (using 2D Sr₂Nb₃O₁₀ and ZnO nanoparticle as examples) on paper. Such paper-based photodetector fully utilizes natural hygroscopicity and softness of paper, showing decent flexibility. Its optoelectronic signal remains stable even after 1000 cycles of bending. To the best of one's knowledge, this is the first photodetector that can tell light intensity and dosage simultaneously. This work introduces a new type of wearable photodetector by structure design and material selection, shedding light on more novel works for convenient and practical photodetection.     

用于粒子场图像速度分析的新型光源装置

介绍了一种用于粒子图像速度分析（ＰＩＶ）的光源装置。利用该装置可在间得到一组相互平行的“光切面”，用于精确、快速地对复杂流场分布进行分析。     

Photoswitch based on bacteriorhodopsin Langmuir–Blodgett films

Langmuir–Blodgett (LB) films of bacteriorhodopsin (bR) without addition of lipids were deposited on indium tin oxide (ITO) conductive electrodes. A sandwich photocell with a juction structure of ITO/bR/electrolyte/ITO has been constructed in which the bR LB film was put into contact directly with an aqueous electrolyte immobilized in an agar gel. Under visible light irradiation a transient photocurrent due to a change in light intensity can be observedl showing the property of vision-imitative material. It can be used as a multiple optical switch, since it gives positive and negative transient photocurrnts during application and removal of light irradiation respectively and has a photoresponse repeatedly in the same direction when the light intensity increases or decreases stepwise. A photoalarm consisting of the bR photocell and an amplifier was set up by utilizing the switching function of the bR LB film.     

Quantum-confined field-effect light emitters: device physics andexperiments

Extended experimental results on three-terminal quantum-confined field-effect light emitters with current injection and field control of luminescent characteristics in the quantum-well structure are reported. By incorporating superlattice buffer layers (SLBLs), the quantum efficiency of the device is dramatically improved and equivalently nonradiative recombination processes are sufficiently suppressed at room temperature. The red-shift of the emission spectra by the quantum-confined Stark effect assures that the electric field is effectively applied to the quantum well. The experimental data on the transient responses of emission intensity to input voltage pulses show fairly good correspondences with theoretical prediction and previous photoluminescence experiments. The authors discuss the ultimate capability of high-speed switching and point that an optical pulse with a duration as short as 30 ps and involving more than 100 photons can be generated by scaling down the size of the device with 1% external efficiency     

Analysis of transient interband light modulation by ultrashortintersubband resonant light pulses in semiconductor quantum wells

We explore the transient characteristics of an interband resonant light modulation process by ultrashort intersubband resonant light pulses in semiconductor quantum wells (QW's). The modulation characteristics in a three-level semiconductor QW system, including the effects due to in-plane momentum, have been investigated by a numerical analysis of the coupled Bloch equations using a density-matrix approach. We have studied the effect of the carrier density and the nature of the intersubband coupling light on the transient absorption features of the interband light. The modulation process has been compared in doped and undoped QW's. The switching behavior of the strong interband light field in presence of a train of intersubband light pulses has also been discussed     

Space charge limitation on the response time of organic photodiodes

The dynamic response of an organic bulk heterojunction photodiode to small changes in applied bias or light intensity is investigated as function of the intensity of a constant background illumination by means of photoimpedance and transient photocurrent measurements. For bias voltages close to the open circuit voltage we find that the response timescale with the square root of the light intensity. The results can be quantitatively explained in terms of a space charge limitation on the photocurrent as predicted by Goodman and Rose (J. Appl. Phys. 42, 2823 (1971)). The relaxation time of the diode at open circuit corresponds to the lifetime of the slowest charge carrier in the diode. This relaxation time is determined by the dielectric constant and the smallest of the two carrier mobilities in the bulk heterojunction. This illustrates the importance of balanced carrier mobilities for obtaining diodes with fast response time at low bias for e.g. imaging arrays.     

助航灯具光强测试系统研究

针对助航灯具的发光特性,提出了一种测试助航灯具出射光强分布的方法。使用线阵CCD作为光电传感器,采集、获取各个方向灯具的光强信号,利用A/D芯片和USB接口芯片实现数据的转化和实时传输。通过改进的Delaunay三角剖分线算法和B样条曲线平滑处理算法的结合,提出了一种快速生成等光强曲线的算法,给出了Matlab软件获得等光强曲线的方法。通过对PAPI灯出射光强的测试及其等光强曲线的拟合,验证了该测试装置可以较好地实现光强测试,所提算法绘制的曲线平滑、速度快。     

Study of the dynamics of excited states in CdS and CuCl by transient grating techniques

Transient grating measurements on sample with an anisotropy or with multiple excited states are described. The general formula for the intensity of the diffracted light from a transient grating in a sample with an anisotropic diffusion coefficient is presented and is applied to CdS. A transient grating spectroscopic technique for a sample with multiple excited states is discussed in detail. In addition to these, the contribution of a population and a thermal grating to the observed signals is discussed.