激光窄脉冲信号探测电路的设计与接收

在激光反射层析成像雷达系统中,激光脉宽越窄,系统的成像分辨率越高。而高带宽、无失真的探测接收电路设计起来较为困难。详细分析了雪崩光电二极管(Avalanche Photodiode,APD)模型及其主要性能参数,并选择了合适的探测器。然后对前置放大电路、主放大电路和可控增益放大电路进行了较为详细的分析,并设计了合适的电路结构。GHz级微弱光电信号在被接收时很容易受到外部噪声的干扰,这会导致接收波形产生畸变。采用电磁辐射屏蔽方法消除了干扰,最终无失真地探测和接收到了1 ns窄脉冲激光信号,满足了激光反射层析成像雷达系统的0.15 m成像精度要求。     

光纤喇曼测温系统中APD增益稳定的研究

分布式光纤测温系统采用APD雪崩光电二极管作为接收器件,它的稳定性对后级的信号处理及系统主要技术指标起着决定性的影响.APD的增益受温度波动影响较大.对APD增益进行了分析,针对分布式光纤测温系统中喇曼光信号极微弱和强噪声的特点,设计了一温控系统和一反馈偏压补偿系统.实验证明温控温度波动小于0.1℃,测试输出电压波动小于0.5 mV,完全满足分布式光纤测温系统对APD增益稳定的高要求.     

机载脉冲式激光测距机接收电路的设计

采用硅雪崩管作为光电传感器,将光背景噪声或被测目标漫反射激光转变为微弱电压脉冲,经过两级低噪声可变增益放大器AD603放大后,信号变为幅度较大的电压脉冲,由可编程逻辑器件处理器在单位时间内收集脉冲个数,通过D/A转换电路驱动高压模块改变APD的偏压,最终设计出机载脉冲式激光测距机灵敏度高的闭环负反馈微弱激光接收电路     

Parametric manufacturing yield modeling of GaAs/AlGaAs multiplequantum well avalanche photodiodes

GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiodes (APD's) are of interest as an ultra-low noise image capture mechanism for high-definition systems. Since literally millions of these devices must be fabricated for imaging arrays, it is critical to evaluate potential performance variations of individual devices in light of the realities of semiconductor manufacturing. Specifically, even in a defect-free manufacturing environment, random variations in the fabrication process will lead to varying levels of device performance, Accurate device performance prediction requires precise characterization of these variations. This paper presents a systematic methodology for modeling the parametric performance of GaAs MQW APD's. The approach described requires a model of the probability distribution of each of the relevant process variables, as well as a second model to account for the correlation between this measured process data and device performance metrics. The availability of these models enables the computation of the joint probability density function required for predicting performance using the Jacobian transformation method. The resulting density function can then be numerically integrated to determine parametric yield. Since they have demonstrated the capability of highly accurate function approximation and mapping of complex, nonlinear data sets, neural networks are proposed as the preferred tool for generating the models described above. In applying this methodology to MQW APD's, it is shown that using a small number of test devices with varying active diameters, barrier and well widths, and doping concentrations enables prediction of the expected performance variation of APD gain and noise in larger populations of devices. This approach compares favorably with Monte Carlo techniques and allows device yield prediction prior to high volume manufacturing in order to evaluate the impact of both design decisions and process capability     

高灵敏度的光子偏振激光雷达系统

在空间目标探测中,由于远距离、小目标的特点,回波信号十分微弱,传统的激光雷达不能很好地探测如此微弱的信号。而且现在空间目标探测不仅需要距离信息,还希望获得目标的强度、偏振等更加多维的信息。提出了基于Gm-APD单光子灵敏度探测器的四路光子偏振探测系统,以Gm-APD探测器的泊松概率响应模型为基础,推导了回波微弱信号的强度解算公式,通过四路的强度解算出回波信号的偏振信息,在实验室搭建了四路Gm-APD光子偏振探测系统的原理样机,并介绍了四路Gm-APD光子斯托克斯参量的探测实验。在平均每个脉冲回波能量为7.7810-19 J的情况下,获得3.95%的线偏振误差和5.84%的椭圆偏振误差的探测结果。     

Gain-bandwidth-limited response in long-wavelength avalanche photodiodes

The gain-bandwidth(GB)-limited response of In0.53Ga0.47As/ InP heterostructure avalanche photodiodes (APD's) and related devices used in long-wavelength digital optical receivers is calculated. We find that these diodes, as currently designed, are useful at bit ratesB lsim 2Gbit/s when employed in conjunction with high-sensitivity optical receivers. Response at higher bit rates may be obtained depending on the details of device design. On the other hand, use of poor-quality receivers that require moderate-to-high values of optimum gain can significantly degrade the performance of heterostructure APD's at high bit rates due to GB limitations. We also show that APD receiver bandwidth can be expressed in terms of the sensitivity obtained using the receiver in conjunction with a p-i-n photodiode. It is found that the response speed of optimized receivers is lowest for an APD effective ionization rate ratio ofk = 0.5.     

雪崩光电二极管恒虚警率控制在激光成像系统中的应用

雪崩光电二极管以其接收灵敏度高，响应速度快等优点，常用于扫描式激光成像系统中，由于雪崩光电二极管的工作电压随背景和温度的变化而变化，因此正确设置其工作偏压，对充分发挥接收系统的探测灵敏度是重要的。主要讨论采用恒虚警率控制法自动设置雪崩光电二极管的偏压，调整噪声门限以获得光电接收系统最佳工作状态。     

Modeling of two-dimensional gain profiles for InP-InGaAs avalanchephotodiodes with a stochastic approach

The two-dimensional (2-D) gain profiles for separate absorption, grading, charge and multiplication (SAGCM) InP-InGaAs avalanche photodiodes (APD's) have been modeled with a stochastic approach. To consider the influence of the curved diffusion edge on the electric field within the periphery region, equations are derived from the cylindrical Poisson's equation. The electric field profiles are computed at various APD radii and the electric field in the multiplication layer is reduced significantly for APD's with a partial charge sheet in the periphery. It is demonstrated by the modeled 2-D gain profiles that the premature edge breakdown can be effectively suppressed for such devices. The modeled 2-D gain profiles for APD's with a partial charge sheet incorporated in the periphery are in good agreement with the experimental results. The results and the uniformity issue of the 2-D gain profiles are discussed. The effect of using curved diffusion interfaces instead of a steep mesa step is also explored; this suggests that the fabrication of a charge sheet mesa step may complicate the gain uniformity issue. From our analyses, we find that the uncertainty and the symmetry of both patterning the charge sheet mesa structure and controlling the diffusion interface between the p⁺ InP top layer and the n^- InP multiplication layer are most likely to affect the uniformity and the symmetry of the 2-D gain profiles for the SAGCM InP-InGaAs APD's     

碲镉汞光子计数型线性雪崩探测器(特邀)

单光子计数技术在弱信号探测和时间测距中具有重大的应用前景。自从20世纪70年代可见光的光子计数系统研发以来,国际上该领域内的研发小组在不断地发展完善光子计数技术,充分放大光子信号,以降低电子设备的读出噪声。电子倍增电荷耦合器件(Electron Multiplying Charge Coupled Devices, EMCCDs)具有更高的量子效率,可替代传统的可见光光子计数系统,但较大的雪崩噪声阻碍了倍增下入射光子数的准确获取。碲镉汞线性雪崩器件(HgCdTe APD)的过剩噪声因子接近1,几乎无过剩噪声;相对于盖革模式的雪崩器件,没有死时间和后脉冲,不需要淬灭电路,具有超高动态范围,光谱响应范围宽且可调,探测效率和误计数率可独立优化,开辟了红外波段光子计数成像的新应用领域,在天文探测、激光雷达、自由空间通信等应用中具有重要价值。美国雷神(Raytheon)公司和DRS技术公司、法国CEA/LETI实验室和Lynred公司、英国Leonardo公司先后实现了碲镉汞线性雪崩探测器的单光子计数。文中总结了欧美国家在碲镉汞光子计数型线性雪崩探测器研究方面的技术路线和研究现状,分析了吸收倍增...     

PIN avalanche photodiodes model for circuit simulation

A circuit model of PIN avalanche photodiodes (APD's) based on the carrier rate equations for circuit simulation is presented. This model is for dc, ac, and transient analysis. As an example, an In_0.53 Ga_0.47As-InP PIN APD is simulated     

激光脉冲弱小回波信号提取方法研究

在激光红外复合制导中,主动激光雷达可以提供探测目标的距离信息,并与红外探测方式实现光电互补,有助于提高复杂战场环境下精确制导的准确率。激光测距时,准确的回波位置检测是确保测距精度的关键。而信噪化是决定精度和作用距离的关键。为了提升脉冲回波信号的信噪比,本文提出了一种结合自相关滤波算法与改进的奇异值分解方法的微弱脉冲提取方法,并分别采用仿真数据和实际采集的脉冲激光回波信号进行去噪实验,实验结果表明,本文所提出的方法能够有效地提升回波信号的信噪比,有助于提高激光测距的精度。     

低抖动准分子激光放大器光源的研究

为了获得低抖动的准分子激光放大器光源,设计了一种以氢闸流管作为高压开关的低抖动准分子激光放大器系统。利用抖动小于4 ns的闸流管触发电路来触发导通氢闸流管,从外部触发信号到准分子光信号之间有一定的延时时间。研究了以氢闸流管作为高压开关的准分子激光放电回路,外部控制信号发生电路产生外部充电信号和出光信号,转换电路将外部充电信号和出光信号转换成固定脉宽的光信号,在实现低抖动出光前,准分子激光放大器系统热平衡过程中会有一定的出光延时漂移现象。讨论了激光运行重复率、激光运行电压和气体状态在热平衡过程中对稳定延迟时间大小的影响。实验表明,在相同运行电压下,稳定延迟时间随着激光运行重复频率的提高而增大;运行电压越高,稳定延迟时间上升的幅度越大。气体恶化后,光脉冲稳定延迟时间变小。激光运行电压和重复频率越高,延时漂移时间越大。在温漂一定时间后,准分子激光放大器内部系统达到热平衡,以外部触发信号为基准,准分子光脉冲信号实现在5、10、15 Hz重复频率下的5 ns内低抖动出光。     

32×32面阵InGaAs Gm-APD激光主动成像实验

近十年来,由于盖革模式APD焦平面探测器在探测灵敏度、空间分辨率和距离分辨率等方面的优势,使得面阵APD激光主动成像技术成为国际上的研究热点。考虑到大气传输特性,InGaAs材料或者HgCdTe材料的面阵APD探测器成为研制首选。在国内自研InGaAs材料的3232像元Gm-APD基础上,搭建了一套1 570 nm激光主动成像实验平台,在成像帧频1 kHz、单脉冲能量2 mJ条件下,获得了外场3.9 km目标的轮廓像,在720 m处能获得目标的清晰表面结构距离像。通过该外场实验,证实了国内自研的面阵Gm-APD探测器性能良好,能够演示外场激光主动成像功能。实验结果表明,1 570 nm面阵APD激光成像雷达成像性能良好,能够实现远距离目标遥感探测,为未来实际应用奠定了良好的研究基础。     

APD单光子探测的电路设计

在气体分析领域,由于分子密度的减小,拉曼技术很难获得足够强的信号,为提高检测灵敏度,利用雪崩光电二极管设计了单光子探测器,来检测微弱的拉曼光。系统围绕APD设计了三个主要模块：偏置/测试电源、温控模块、信号调理。测试了系统的暗计数率,并用标准气校验了系统的准确度。实验结果表明：标准差最大为0.905,按总量程计算可得重复性相对偏差为0.905%,而非线性误差取最大引用误差0.13%。其多次测量结果的线性度很好,能够用于线性检测。     

Avalanche photodiodes with separate absorption and multiplication regions grown by metalorganic vapor deposition

InP/InGaAs avalanche photodiodes with separate absorption and multiplication regions (SAM APD's) have been fabricated from wafers grown by atmospheric-pressure metalorganic chemical vapor deposition. These APD's exhibit low dark current and good quantum efficiency. The pulse response exhibits the two-component response typical of the SAM-APD structure. The slow component is 6 ns and the fast component is 100 ps.     

高功率光纤激光器反向光放大和损伤特性数值分析

利用速率方程模型对主振荡?功率放大器结构的1 μm波段掺镱（Yb）高功率光纤激光器中存在连续波反向信号光时的功率特性进行了理论分析,结果显示反向信号光功率会被高功率激光放大器所明显放大,10 kW级的光纤激光器中,100 W的反向信号经过放大器后功率会被放大至kW量级;与此同时,反向信号放大过程对反转粒子数的消耗会导致激光器的正向输出功率的严重下降。另外,反向信号放大也会导致放大器输出端的激光功率过强,加剧泵浦吸收和受激发射过程,增加该处的热负载、导致温度大幅上升100 ℃以上,对稳定性产生潜在影响。反向信号导致振荡器提供的正向种子光功率波动和下降时,正向信号不能充分饱和有源光纤中的增益,会进一步加强反向信号在主放大级中的放大作用,进而对系统造成更严重的影响。提高正向种子光功率、增强正向信号对激光增益的饱和作用,有助于抑制反向信号的放大过程,但需综合考虑种子源稳定性、热负载、热致模式不稳定和受激拉曼散射等因素合理选择种子光功率。     

InGaAs/InP盖革模式雪崩焦平面阵列的研制

设计制作了一种由InGaAs/InP雪崩光电二极管阵列与时间计数型CMOS读出电路组成的8×8阵列规格盖革模式雪崩焦平面阵列(GM APD FPA).雪崩光电二极管采用SAGCM结构,在盖革模式下工作具有单光子探测灵敏度;时间计数型CMOS读出电路在每个单元获取光子飞行时间,实现纳秒级的时间分辨率,并完成雪崩淬灭功能.测试结果表明,倒装混合集成的GM APD FPA器件暗计数率(DCR)均值为32.5 kHz,单光子探测效率(PDE)均值为19.5％,单元时间抖动为465 ps,实现了光脉冲时间信息的探测,验证了盖革模式雪崩焦平面阵列技术及其在三维成像中应用的可行性.     

输出高重复频率脉冲列的D型双包层掺Yb3+光纤放大器

利用5 m长的D型双包层掺Yb3 光纤,采用声光调制锁模信号系统,实验上成功研制出输出320 MHz的高重复频率脉冲列的光纤放大器,得到了20 dB的增益输出,输出激光波长1064 nm,输出平均功率1.02 W,该光纤放大器可作为空间激光通信系统发射源.整个实验系统装置由作为信号源的特高重频脉冲列激光器、作为放大环节的光纤放大器和绿光倍频三个部分组成,另外对光纤放大器自激振荡谱线的各影响因素做了一些相关的实验研究,并对结果进行了分析讨论,提出了改进措施.     

The effect of nonuniform gain on the multiplication noise of InP/InGaAsP/ InGaAs avalanche photodiodes

We have investigated the effect of spatial gain uniformity on the multiplication noise of InP/InGaAsP/InGaAs avalanche photodiodes (APD's) with separate absorption, "grading," and multiplication regions. APD's with localized regions of high gain exhibit higher excess noise factors and poorer Performance in lightwave receivers than those with uniform gain.     

1.06μm注入锁定增益开关半导体激光器特性分析与功率放大研究

报道了1.06 m增益开关半导体激光器的详细特性分析和功率放大研究。用高频正弦信号调制中心波长1.06 m的F-P腔半导体激光器得到脉宽约为100 ps、平均功率约为20 mW,重频从500 MHz到2 GHz连续可调的稳定短脉冲激光输出。采用注入锁定改善增益开关半导体激光器的输出特性。研究和分析了调制信号的频率、功率和偏置电流的大小以及注入锁定的功率、温度对激光器输出特性的影响。将该激光器作为种子,用108 W的抽运光进行两级全光纤功率放大得到了82 W的高功率输出,光光转换效率达到76%。