毫秒脉冲激光致硅光电二极管电学损伤的有限元分析及实验研究

为了研究毫秒脉冲激光致硅基PIN光电二极管电学损伤,基于热传导及弹塑性力学理论,在光电二极管内部材料各向同性并且P-I-N三层结构之间满足温度连续和热流平衡条件下,建立毫秒脉冲激光辐照硅基PIN光电二极管二维轴对称模型,采用有限元方法模拟分析了1064 nm Nd:YAG毫秒量级脉冲激光辐照硅基PIN光电二极管的温度场与应力场分布,并实验测量了硅基PIN光电二极管实验前后的电学参数.结果表明,激光辐照硅基PIN光电二极管时,温升使材料表面熔融、烧蚀,并且在空间上存在温度梯度变化,即激光辐照产生的热与应力使光敏面及硅晶格晶键损伤,最终造成光电探测器的探测性能下降.研究结果可为毫秒脉冲激光辐照硅基PIN光电二极管电学损伤机理奠定基础.     

硅光电二极管作为CsI(Tl)晶体读出元件的实验研究

报道了硅光电二极管作为CsI(Tl)晶体读出元件的实验研究.测量了日本Hamamatsu生产的两种硅光电二极管的读出性能,包括能量分辨率与偏压、成形时间、灵敏面积和晶体尺寸的关系.     

北京同步辐射装置软X光束线通量谱的绝对测量与计算

在北京同步辐射装置(BSRF)上用全吸收平行板充氙电离室作一级标准探测器,对硅光电二极管(AXUV—100)的效率在光子能量5—6.5keV进行了标定,建立了二级标准探测器;AXUV—100硅光电二极管在50eV-6keV有很好的线性响应,将其在硬X射线波段已标定的效率曲线外推到软X射线波段,并对BSRF3B1A和4B9B光束线在软X射线波段光子通量谱进行了初步地测量,测量结果与理论计算结果较为符合.在3B1A软X光学实验站,利用二级标准探测器对用于惯性约束聚变(ICF)的软X光探测器的灵敏度进行了标定,并取得了满意的结果.     

硅光电二极管的双光子响应

报道用连续光1.3μmInGaAsP半导体激光器探测硅光电二极管中的双光子响应(我们把倍频效应和双光子吸收统称为双光子响应).通过实验,证明在硅光电二极管中必然有倍频吸收引起的光电流存在.     

硅光电二极管光谱响应率的测量

本文介绍测量硅光电二极管光谱响应率的实验装置及测量方法,并总结了在测量中要注意的问题,为今后的实验研究提供了有益的经验.     

硅光电二极管激光损伤阈值随激光脉宽的变化

 对飞秒激光辐照下硅光电二极管损伤阈值进行了实验测量，对从1s到60fs不同脉宽激光辐照下硅光电二极管损伤阈值进行了讨论。实验数据表明，在1s到10ns脉宽范围内损伤所需能量密度近似而非严格地与脉宽的平方根成正比。信号分析表明硅光电二极管的损伤主要由热效应造成，而60fs激光辐照下的损伤阈值为0.1J/cm2，明显偏离普通温度分布预言的趋势。     

飞秒激光微构造硅光电二极管的光电响应

在一定条件SF6气体氛围中,硅可在飞秒激光辐照区产生m量级的尖峰结构。针对不同尖峰高度的微构造硅,在不同温度下退火,采用电子蒸发的方法在正反面分别镀上铝电极,制备出了飞秒激光微构造光电二极管,并测试了其光电响应。实验结果表明:飞秒激光微构造光电二极管的响应随微构造硅光电二极管的尖峰高度和退火温度的不同而不同。尖峰高度为3～4 m的样品在973 K温度退火30 min后,响应度可达0.55 A/W。即使在1100 nm波长处,这种新型的硅光电二极管的响应仍可高达0.4 A/W。     

基于FPGA的单光子雪崩光电二极管的标定系统

目前单光子雪崩光电二极管的标定系统主要是通过分立的通用测试仪器搭建而成。由于单光子雪崩光电二极管的工作模式存在多样化的特点,因此使用该方法搭建的标定系统具有缺乏兼容性、复杂度高、集成化程度低等不足。针对这些问题,本文发展了一种基于现场可编程门阵列的,可以兼容各种雪崩抑制模式的,高度集成化的多种材料体系器件兼容的单光子雪崩光电二极管标定系统。该系统使用现场可编程门阵列替代函数发生器、脉冲产生器和计数器等仪器设备,并利用现场可编程门阵列实现不同雪崩抑制模式下雪崩光电二极管的驱动电路和标定光源的智能切换,从而大幅提高了系统的兼容性和集成化程度,也进一步降低了系统的复杂度、提高了系统的稳定度。文中,我们利用该系统对工作在主动抑制模式的硅雪崩光电二极管和门控盖革模式的铟镓砷/铟磷雪崩光电二极管进行了标定实验。标定结果显示所标定的硅雪崩光电二极管的最大探测效率为49.82%,对应暗计数为1.41kHz;铟镓砷/铟磷雪崩光电二极管的最大探测效率为7.14%,对应暗计数为831 Hz,在探测效率为5%时,后脉冲的概率为5.84%。实验结果表明,我们为单光子雪崩光电二极管标定提供了一种便捷的一体化解决方案,提高了单光子雪崩光电二极管的标定效率和标定系统的实用化程度。     

光电耦合器的原理及应用

光电耦合器是一种光电结合的器件,它由两部分组成:输入端由发光器件组成;输出端由光接收器件组成.目前国内外的光电耦合器输入端大都使用发光二极管——砷化镓发光二极管,输出端大都使用硅光电二极管或硅光敏三极管,结构见图1.     

硅光电二极管光谱响应度的分析

从光电二极管的工作原理出发,对硅光电二极管的光谱响应度进行了论述.分析表明,入射光子的能量、材料的禁带宽度和吸收系数是光谱响应曲线具有波长选择性的主要原因.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.