高功率808nm InGaAsP—GaAs分别限制结构的半导体激光器

介绍了研究分别限制结构ＩｎＧａＡｓＰ－ＧａＡｓ半导体激光器所得到的最新成果。利用引进的俄国技术，基于量子阱结构的ＩｎＧａＡｓＰ－ＧａＡｓ激光器，可用短时间液相外延技术制造。在ＧａＡｓ衬底上制成的ＩｎＧａＡｓＰ－ＧａＡｓ分别限制结构的激光器，主要参数如下：发射波入λ＝８０８ｎｍ，阈值电流密度Ｊ＝３００Ａ／ｃｍ＾２，对于条宽ω＝１００μｍ的激光器，连续功率为１－２Ｗ。     

1．55μm InGaAsP／InP应变量子阱激光器的LP－MOCVD生长

本文首次报导了生长温度为５５０℃，以三甲基镓（ＴＭＧａ）和三甲基铟（ＴＭＩｎ）为Ⅲ族源，用低压金属有机物气相沉积（ＬＦＭＯＣＶＤ〕技术，高质量１．６２ｕｍ和１．３ｕｍＩｎＧａＡｓＰ及Ｉｎ０．５７Ｇａ０．４３Ａｓ０．９８Ｐ０．０４／Ｉｎ０．７３Ｇａ０．２７Ａｓ０．６Ｐ０．４量子阶结构的生长，并给出了１．５５ｕｍＧａＡｓＰ／ＩｎＰ分别限制应变量子阱结构激光器的生长条件，激光器于室温下脉冲激射，其阈值电流密度为２．４ｋＡ／ｃｍ２。     

垂直电子耦合InGaAs量子吉的光学特性

报导了ＩｎＧａＡｓ／ＧａＡｓ和ＩｎＧａＡｓ／ＡｌＧａＡｓ垂直耦合量子结在注入式激光器的制备工艺及其光致荧光谱，量热吸收谱和电致荧光谱的特性，该激光器的连续波波发光功率在室温下可达１Ｗ。     

单模光纤中Raman光放大

本文报道在单模光纤中，背向受激拉曼散射（ＢＳＲＳ）对通信光的光放大研究。所用泵浦源为声光０开关Ｎｄ￣（＋３）：ＹＡＧ激光器，工作波长１．０６４μｍ。信号源为ＩｎＧａＡｓＰ半导体激光器，工作波长１．３０μｍ。在１．３０μｍ处实现了Ｒａｍａｎ光放大，增益达１９．４ｄＢ以上，增益系数为２．３×１０￣（－１２）ｃｍ／ｗ。     

808nm准连续阵列半导体激光器

报道了８０８ｎｍ无铝ＩｎＧａＡｓＰ／ＧａＡｓ高功率连续阵列半导体激光器,在频率１００Ｈｚ,脉冲宽度２００μｓ,占空比达２０％时,单阵列条的输出光功率室温下达到３７Ｗ。     

晶片融合产生长波低阈值垂直腔激光器

日本ＮＴＴ光电实验室的研究人员演示了一种以双ＩｎＧａＡｓ／ＩｎＰ－ＧａＡｓ／ＡｌＡｓ分布布喇格反射器为基础的１．５５μｍ输出垂直腔表面发射激光器（ＶＣＳＥＬ）。靠晶片融合进行的设计，其不匹配位错密度低于ＩｎＰ／ＧａＡｓ界面上的异质外延生长。这种直径为２５μｍ的器件在２３℃时的阈值电流为８．８ｍＡ，阈值电压为２．１Ｖ。在１０ｍＡ时实验了１．５５μｍ发射，最大输出功率为７μｗ。研究人员希望通过优化底部反射率提高最大输出功率。他们指出，长波ＶＣＳＥ有许多优点，包括在晶片融合前便于作谐振腔波长试验，以及…     

高功率梯度折射率分别限制异质结构InGaAs/AlGaAs应变双量子阱激光器

采用金属有机化合物气相淀积（ Ｍ Ｏ Ｃ Ｖ Ｄ）方法成功地研制了具有两对梯度折射率（ Ｇ Ｒ Ｉ Ｎ）异质结结构的 Ｉｎ Ｇａ Ａｓ／ Ａｌ Ｇａ Ａｓ 应变双量子阱激光器。该激光器的波长为 ９７０～９８２ ｎｍ ,室温连续工作阈值电流密度为１４０ Ａ／ｃｍ ２, 工作在０．９ Ａ 时单面连续输出光功率为５２０ ｍ Ｗ , 工作在２．０ Ａ 时, 连续输出光功率为 １．４９ Ｗ , 最高功率可达 ２．４ Ｗ 。微分量子效率高达０．８３ Ｗ ／ Ａ。     

产生1．3μm辐射的InAsP量子势阱

产生１．３μｍ辐射的ＩｎＡｓＰ量子势阱日本Ｆｕｒｕｋａｗａ电气工业公司和光电技术研究公司合作研制成功１．３ｕｒｎ激光器。此激光器采用ＪｎＡｓＰ而不是采用ＧａｌｎＡｓＰ或ＧａｌｄｅＰ作为加载层量子势价结构中的激活区。与普通材料相比，ＩｎＡＳＰ结构的晶体...     

高功率梯度折射率分别限制异质结构InGaAs／AlGaAs应变双量子阱？…

采用金属有机化合物气相淀积（ＭＯＣＶＤ）方法成功地研制了具有两对梯度折射率（ＧＲＩＮ）异质结构的ＩｎＧａＡｓ／ＡｌＧａＡｓ应变双量子阱激光器。该器的波长为９７０－９８２ｎｍ,室温连续工作阈值电流密度为１４０Ａ／ｃｍ＾２,工作在０．９Ａ时单面连续输出光功率为５２０ｍＷ,工作在２．０时,连续输出光功率为１．４９Ｗ,最高功率可达２．４Ｗ,微分量子效率高达０．８３Ｗ／Ａ。     

SCH量子阱激光器的光学限制特性

通过对描述半导体激光器基本光波导方程的数值求解，分析了ＡｌＧａＡｓ／ＧａＡｓ分别限制量子阱激光器的光学限制特性，比较了不同缓变结构及多量子阱结构的光学限制因子。     

光A/D转换器中飞秒脉冲谱分割的Matlab仿真(英)

介绍了一种用于A/D转换的120 GS/s光采样时钟。讨论了生成这种采样时钟的方法,以及一种以其为基础的全光示波器。用Matlab实现飞秒激光脉冲谱分割以及复用的仿真,并进一步说明了用生成的光脉冲序列进行采样时需要考虑的问题。将Optisystem的仿真结果与Matlab的结果进行对比,并用Matlab计算的衰减率结果对Optisystem生成的采样光序列接行了优化。     

功率谱反演大气湍流随机相位屏采样方法的研究

从产生大气湍流随机相位屏的功率谱反演法原理出发,分析了均匀采样造成的随机相位屏大量低频信息泄漏的不足,提出利用非均匀采样方法对功率谱进行滤波产生随机相位屏.建立了非均匀采样模型,并分析比较了两种采样方法覆盖的采样频率范围和单边采样频率区域的湍流功率,理论证明了非均匀采样功率谱反演产生大气湍流随机相位屏的可行性和有效性.针对大气湍流的Kolmogorov谱,分别仿真计算了两种采样模型下功率谱反演生成的大气湍流随机相位屏.仿真结果表明,在不增加采样点和计算量条件下,非均匀采样方法生成的大气湍流随机相位屏具有丰富的低频和高频信息,有效改善了传统功率谱反演大气湍流随机相位屏时低频信息严重不足的缺陷.     

Integration of a Proposed All-Optical Analog-to-Digital Converter using Self-Frequency Shifting in Fiber and a Pulse-Shaping Technique

Integration of a proposed all-optical analog-to-digital (A/D) converter is described. To realize a high-speed and highthroughput system, optical A/D conversion has attracted much attention. A/D conversion generally consists of three processes of sampling, quantization and coding. Whereas an optical sampling technique has already been realized, there have been few investigations on the optical quantization and optical coding technique. We previously proposed an alloptical A/D converter which realizes both optical quantization and optical coding. In this paper, we integrate the proposed all-optical A/D converter to improve its performance and stability. We verify the operation of the integrated all-optical A/D converter composed of a short high nonlinear fiber, arrayed waveguide gratings and variable optical attenuators.     

Optical A/D Conversion by Time-Interweaved Sampling

A time-interweaved sampling scheme for optical A/D conversion is proposed, and to demonstrate this technique 2.5 GHz sine microwave signal is sampled at a rate of 16×2.5 GHz. 29dB signal-to-noise rate is acquired after processing the experimental data. In this paper we analyse the impacts of the imperfect optical sampling pulses, including the waveform, pulse width, and time jitter, and then discuss the way to improve the sampling precision.     

Beamforming with a reduced sampling rate

The beamforming process requires a high delay resolution to avoid the deteriorating effects of the delay quantization lobes on the image dynamic range and signal to noise ratio. Wideband transducers require delay resolutions in the order of 1/16 the signal period. If oversampling is used to achieve this timing resolution, a huge data volume has to be acquired and processed in real time. This is usually avoided by sampling just above the Nyquist rate and interpolating to achieve the required delay resolution. However this increases the hardware complexity. Baseband sampling has been alternatively proposed with sampling rates as low as the transducer frequency or even lower. This approach uses two A/D converters and processing chains for every channel, thus doubling the hardware requirements. Quadrature sampling can be used instead with a single A/D converter, but the sampling rate must be a multiple of four times the transducer frequency, decreasing the application flexibility. Furthermore, it produces relatively high errors in the detected envelope if wideband transducers are used. This work presents a new approach, the selective sampling technique (SST), which keeps the lowest sampling rate required by the imaging process or the signal bandwidth (whatever is larger) and, at the same time, provides a high delay resolution to keep the highest image dynamic range. The SST is based on a second order sampling process which, differently from the mentioned approaches, does not pose any constraints in the time interval between samples and produce lower errors in the detected envelope. The hardware requirements are low (a single A/D converter and processing chain for every transducer element), working at the lowest data rate compatible with the Nyquist criterion, thus reducing the data bandwidth. Furthermore, the sampling points can be also freely chosen, so that the SST simplify the usually required scan conversion process to a simple linear interpolation easily carried out by software in real-time.     

快速电信号的外电光采样测量系统

建立了小型适用的外电光采样系统,利用增益开关半导体激光器产生的皮秒超短光脉冲做为取样门,以LiTaO₃电光探头作为电场传感器,实现了对梳状波电脉冲波形的光学采样测量,测量结果与用采样示波器测量的结果相符.分析了系统的主要性能,获得了25ps的时间分辨率及20mV/√Hz的电压灵敏度.实验分析了电光探头对系统测量精度的影响.同时用该系统测量了共面微带传输线的传输特性.     

抽样法与灵敏度法k_(eff)不确定度量化

核反应堆的中子学模拟计算中,核数据的不确定度导致的积分量计算结果的不确定度,通常采用基于微扰理论的灵敏度与不确定度分析方法 (简称灵敏度法)量化.灵敏度分析法原则上只适用于线性模型,且一般输运计算程序难以直接进行灵敏度分析.而抽样法直接抽样核数据输入中子学计算程序进行计算,通过对计算结果的统计分析评估计算量的不确定度.抽样法易于实现、计算精确、且适用性强.在灵敏度分析与不确定度量化程序SURE中,增加了抽样法不确定度的量化功能.为将抽样法不确定度量化应用于复杂问题的模拟计算,需对其进行细致的考核.为此,选取简单的临界基准实验模型,分别采用灵敏度分析法和抽样法进行不确定度量化,得到了各核素各反应道核数据导致的k_(eff)计算不确定度.对比显示,两种方法的不确定度计算结果有很好的符合,验证了SURE程序抽样法功能的正确性.抽样法计算的k_(eff)符合正态分布,说明在一般核数据的不确定度范围内,k_(eff)与核数据近似成线性关系,利用灵敏度分析法评估k_(eff)计算值的不确定度是适用的.     

Modulation bandwidth and noise limit of photoconductive gates

The modulation bandwidth and noise limit of a photoconductive sampling gate are studied by reducing the parasitic capacitance and leakage current of the sampling circuit using an integrated junction field-effect transistor (JFET) source follower. The modulation bandwidth of the photoconductive sampling gate is limited by the external parasitic capacitance, and its efficiency is found to saturate at a laser gating power of about 1 mW. It is determined that the noise of the photoconductive sampling gate is dominated by the photovoltaic current due to the gating laser amplitude fluctuation. A minimum noise level of 4 nV Hz^–1/2 has been measured, and an enhancement in signal-to-noise ratio by a factor of >45 has been achieved after the integration of the source follower with the photoconductive sampling gate. The JFET source follower serves to increase the modulation bandwidth of the photoconductive sampling gate by about 15 times and buffer the charge of the measured signal using its extremely high gate input impedance. The performance of the photoconductive sampling gate in regard to invasiveness and gating efficiency has been optimized, while a picosecond temporal resolution has been maintained and the signal-to-noise performance has been enhanced using a gating laser power as low as 10 W.     

Waveform timing performance of a 5 GS/s fast pulse sampling module with DRS4

We first clarify timing issues of non-uniform sampling intervals regarding a 5 GS/s fast pulse sampling module with DRS4. A calibration strategy is proposed, and as a result, the waveform timing performance is improved to below 10 ps RMS. We then further evaluate waveform-timing performance of the module by comparing with a10 GS/s oscilloscope in a setup with plastic scintillators and fast PMTs. Different waveform timing algorithms are employed for analysis, and the module shows comparable timing performance with that of the oscilloscope.     

基于能量密度分布的辐射源粒子空间抽样方法研究

利用隐式蒙特卡罗方法模拟热辐射光子在物质中的输运过程时,物质辐射源粒子是需要细致处理的物理量.传统的物质辐射源粒子抽样方法是体平均抽样方法,对于大多数问题,这样处理不会带来大的偏差.但是对于一些辐射吸收截面大、单一网格内温差显著的问题,体平均抽样方法的计算结果偏差较大.分析了产生偏差原因,提出一种基于辐射能量密度分布的辐射源粒子空间位置抽样方法,并推导了相应的抽样公式以解决此类问题.数值实验表明,新方法计算结果明显优于原方法且与解析结果基本一致.