FTIR测量的宽波数范围发射光谱强度校正

针对采用FTIR方法在宽波数范围内测得不同样品的发射光谱在强度上难以做定量比较的困难,提出了一种简便可行的校正方案,即通过计算发射谱仪器函数来进行强度校正;对其可行性、限制因素及注意事项进行了详细讨论.以一组覆盖宽波数范围的样品为例用此方案测量校正了室温下测得的光荧光谱,并对校正前后的结果进行了比对分析,获得了与实际符合的结论.结果表明采用FTIR测量方法并结合适当的校正方案可以获得宽波数范围内的有效发光强度信息.     

抑制甚长波红外传感器光谱响应非线性效应的研究

甚长波红外传感器响应光谱测量的过程中,探测器以及前置放大器均工作于线性工作区是必要的,否则由傅里叶变换光谱仪(FTIR)测得的响应光谱,在某些情况下仪器信号会发生饱和,从而引起响应光谱畸变,直接影响测试结果以及后续的分析工作.文中对利用FTIR测量光电探测器响应光谱时,光谱仪信号的饱和问题进行研究,改进了常规测试方法,提高了测试准确度.     

半导体二极管

发展了一种红外发光二极管(IRED)辐射波长和强度的积分式(非分光)测试技术。它采用两只不同光谱响应的光电探测器,一只探测器的相对光谱响应在足够宽光谱范围内修正成常数,另一只探测器电按要求用滤光器修正。辐射强度可由相对光谱响应为常数的探测器测量;通过对测得的两个光探测器光电流之比与波长关系的数据进行处理,可以快速获得 IRED的辐射波长。以 MCS-51单片机和上述两个光电探测器及它们的有关电路组成了一台样机实现这个原理。仪器具有高速实时,稳定性好及智能化的优点。参5     

集成光电探测器绝对光谱响应度的研制

分析了光电探测器的结构及光谱响应度的测试原理,基于LabVIEW图形化软件,研制了一套0.2～1.1 μm的光电探测器绝对光谱响应度测试装置.本系统采用单光路小光点标准替代法进行测量,系统组成灵活并可扩展,配合自行研制的驱动电路和采样保持电路,可以满足不同器件的需要.采用本系统对上海技物所研制的多种集成光电探测器的绝对光谱响应度进行测试,测试结果表明了系统的可行性.     

光伏探测器响应非线性的机理分析

随着光伏探测器在傅里叶变换红外(FTIR)光谱探测领域的广泛应用，光伏型器件的响应非线性现象逐渐成为影响FTIR光谱反演精度的关键问题。文章对光伏探测器的响应非线性进行研究，首先，总结了光伏探测器的一般原理与等效电路；然后，对导致探测器出现响应非线性的内部效应与外部因素进行分析；最后，总结了内外因素之间的关联，并在结论中给出了对探测器进行非线性校正的工作方向。这对揭示半导体器件对不同通量辐射的响应规律、对于改善研究光伏探测器的非线性问题以及提高FTIR光谱探测精度具有重要的意义。     

红外激光辐照下光电探测器光谱响应度的研究

响应度R是反映探测器性能的一项重要指标.当光电探测器被激光损伤后,其响应度R将会下降.文中探讨了强激光对光电探测器的损伤机理,对不同功率密度强激光作用下探测器的光谱进行了测量,研究了探测器在强激光辐照下探测器响应度变化规律.对光电对抗以及光电探测器的抗激光损伤研究具有一定的参考价值.     

TGS和LiTaO_3探测器可见区和近红外区光谱响应的测量

国产TGS(硫酸三甘肽)和LiTaO_3(钽酸锂)探测器是近两年研制成功的热释电探测器。可用于可见、近红外和远红外的分光测量。为了精确地探测和研究辐射源的光潜能量分布,必须知道所用探测器的光谱响应,所以光谱响应是探测器的重要性能指标之一。探测器光谱响应的测量,一般多以热电偶作为无选择性探测器进行比较测量。但由于热电偶的光谱响应对所有波长并不都是常数,其相对光谱响应如图1所示,所以对比法测量有不足之处。本测量采用标准辐射源法直接测量和计算了TGS和LiTaO_3探测器在可见区和近红外区的光谱响应,并附带测量了光电倍增管和硅光电池的光谱响应,以资比较。     

硅陷阱探测器在325～980nm波段的绝对光谱响应率和量子效率测定

为获得硅陷阱光电探测器在325～980 nm区间的绝 对光谱响应率和量子效率,采用低温辐射计对这一波段内的11个波长点处的 绝对光谱响应率 进 行了测量,其不确定度优于0.05%;利用Geist的经典量子效率模 型对硅 陷阱探测器的内量子效率进行了模拟,并与实验得出的内量子效率进行了比较 。 结果显示:在325～980nm 波段的中间部分,理论计算与实验测 得值 相对偏差小于0.03%。     

高能激光测量中的光强探测器面响应校正方法

为了降低光强探测器面响应非均匀性对高能激光惯性约束聚变(ICF)装置近场参数测量的影响,提出了一种高能激光近场参数测量中的光强探测器面响应非均匀性校正方法.理论方面推导了基于高能激光近场空域评价因子的多点线性定标校正模型,并设计及搭建了高均匀性线性输出的光强探测器面响应非均匀性自动校正装置.为了验证所提方法的有效性,对某型号科学级CCD的面响应非均匀性进行校正,探测器面响应调制度由1.42降至1.08,对比度由0.014降至0.004,相比两点定标方法,采用文中所提方法校正后光强探测器的均匀性大幅提高.结果 表明,该方法可为高能激光ICF装置参数测量中的光强探测器面响应均匀性校正提供一种有效的技术手段.     

光电成像系统的绝对光谱响应效率测量及分析

为了准确测量光电成像系统的绝对光谱响应效率,采用光学系统光能量传递公式以及图像传感器的物理模型,得到了光电成像系统绝对光谱响应效率的计算公式,在此基础上设计了基于积分球、多光谱发光二极管光源、标准探测器及透射式平行光管的光电成像系统绝对光谱响应效率测量装置,并对光谱响应效率已知的可见光数字相机进行实验测量和分析。结果表明,在380nm~1100nm波长范围内测量装置测得的可见光数字相机的绝对光谱响应效率与标准值具有较好的一致性,最大相对误差为1.7%,各波长点的测量不确定度在置信概率为95%时均小于0.2%,满足一般的测量要求。该装置能够准确地对光电成像系统的绝对光谱效应效率进行测量。     

Transit-time limited high-frequency response characteristics of MSMphotodetectors

A simplified, but useful, one-dimensional transit-time limited frequency domain current response model of MSM photodetectors is presented. The model includes the effects of unequal velocities and lifetimes governing the lateral transport of photogenerated holes and electrons in the absorption layer. Normalized frequency response curves depicting the amplitude and phase versus the frequency are presented using the transit-time ratio as a parameter. The usefulness of the analytical response amplitude curves for the extraction of hole and electron transit times has been demonstrated by regressively fitting them with the measured results obtained from practical MSM photodetectors     

Ultraviolet photodetectors based on natural diamond

Ultraviolet photodetectors based on natural 2a diamond are fabricated and examined. From the capacitance-voltage characteristics and capacitance spectra, it is found that the ac conductivity of photodetectors is purely capacitive and that the capacitance of the samples is determined by their geometry. The dynamic range of the photodetectors is found to be no less than 10⁴. The measured photosensitivity spectra and current-power characteristics bear evidence of the high sensitivity and selectivity of the photodetectors in the UV region, which favor their application for the detection of weak radiation signals, including detection during day-time.     

特殊图案透明欧姆接触微结构提高谐振腔增强型光探测器的响应性能

为解决谐振腔增强型(RCE)光探测器的耦合效率和响应速率的矛盾,提出了采用特殊图案透明欧姆接触的微结构及其制备工艺方案,从而使得在器件入光面积不变的情况下,欧姆接触部分的总面积显著减小,在不影响器件量子效率的前提下达到减小电容、提高响应速率的目的。在台面面积为50μm×50μm的情况下,获得了18 GHz的响应带宽。研制的谐振腔增强型光探测器的响应速率得到了显著的提高。     

Performance of Partial Response CPM in the Presence of Adjacent Channel Interference and Gaussian Noise

Partial response continuous phase modulation (CPM) schemes have found wide acceptance because of their compact spectra and comparable performance with other traditional modulation schemes. Although optimum receivers are complex, simple suboptimum receivers are found to yield very good performance in special cases. Performance of such modulation schemes is of interest in a multiple user environment where adjacent channels are spaced closely to improve the system capacity. This paper presents the performance of partial response CPM in the presence of adjacent channel interference and Gaussian noise. The meansquare crosstalk in CPM systems employing MSK-type receivers is formulated. Based on this formulation, a number of modulation schemes employing different receiver filters are analyzed for their ACI rejection. Comparison of results proves that receiver filters, in addition to the spectral occupancy of the signal, play an important role in deciding the crosstalk. The error performance of various schemes evaluated using simulation technique is compared, and it is found that in the presence of adjacent channel interference, certain schemes perform better than minimum shift keying (MSK). The results of the simulation further prove the inadequacy of Gaussian assumption for the adjacent channel interference. It is seen that judicious choice of modulation scheme and receiver filter can result in better spectrum utilization.     

Analysis and spectral characteristics of a spread-spectrumtechnique for conducted EMI suppression

Frequency modulation (FM) and random switching methods have been used for reducing conducted electromagnetic interference (EMI) in power converters. Limited theoretical studies and comparisons of these schemes, however, are available. In this paper, a detailed analysis and the spectral characteristics of a random carrier-frequency (RCF) technique for suppressing conducted EMI in an offline switched-mode power supply are presented. The analysis provides a theoretical platform for studying the characteristics of this random switching scheme. The level of randomness is defined for the RCF scheme and varied in the converter example so that the effects on the power spectra can be demonstrated. Theoretical predictions of the spectral characteristics of this scheme are confirmed with measurements. The RCF scheme has been compared with the standard constant-frequency pulsewidth modulation (PWM) scheme and the FM scheme. Comparisons of their spectral performance show that the RCF scheme has better conducted EMI suppression than the FM and standard PWM schemes     

基于K-均值聚类和传统递归最小二乘法的高光谱图像无损压缩

针对基于预测的高光谱图像无损压缩算法压缩比低的问题,该文将聚类算法与高光谱图像预测压缩算法相结合,提出一种基于K-均值聚类和传统递归最小二乘法的高光谱图像无损压缩算法。首先,对高光谱图像按光谱矢量进行K-均值聚类以提升同类光谱矢量间的相似度。然后,对每一聚类群分别使用传统递归最小二乘法进行预测,消除高光谱图像的空间冗余和谱间冗余。最后,对预测误差图像进行算术编码,完成高光谱图像压缩过程。对AVIRIS 2006高光谱数据进行仿真实验,所提算法对16位校正图像、16位未校正图像和12位未校正图像分别取得了4.63倍,2.82倍和4.77倍的压缩比,优于同类型已报道的各种算法。     

Optimization of high-speed metal-semiconductor-metal photodetectors

Circular-aperture Metal-Semiconductor-Metal (MSM) photodetectors have been fabricated in order to decrease the device capacitance. The frequency-response of the MSM photodetectors has been calculated using a first-order approximation. The design of the circular-aperture detectors and conventional square-aperture detectors has been optimized using this approximation. The largest 3 dB bandwidths are obtained with 33 fingers for the circular detectors and 29 for the square detectors. These numbers do not change regardless of the size of the MSM photodetectors     

AlxZn1-xO合金MSM光电探测器的研究

在Si衬底上磁控溅射制备AlxZn1-xO(AZO)合金薄膜,在其上真空蒸发Ni/Au叉指电极获得金属-半导体-金属(MSM)结构光电探测器.采用UV-Vis-Nir分光光度计测量AZO系列薄膜的光吸收特性,观察到AZO 合金薄膜的光学吸收带边随Al含量增加明显蓝移.测试AZO探测器的电流电压特性、时间特性和响应光谱发...     

20 GHz bandwidth InGaAs photodetector for long-wavelength microwave optical links

InGaAs photodetectors have been fabricated having a packaged RC plus transit-time-limited bandwidth of 20 GHz and a fibre-coupled responsivity of 0.55 A/W. Using a directly modulated InGaAsP diode laser, the photodetector optical frequency response was measured 3 dB flat to 17 GHz, the bandwidth limit of the laser.     

Growth and characterization of n-type InP/InGaAs quantum well infrared photodetectors for response at 8.93 µm

We present experimental results on the growth and characterization of n-type InGaAs/InP quantum-well intersubband photodetectors for use at 8.93 μm. High-quality InGaAs/InP multiple quantum wells were grown by gas source molecular beam expitaxy, and then characterized by double-crystal x-ray diffraction and cross-sectional transmission electron microscopy. Based upon the structural parameters determined by these methods, the photocurrent response spectra were simulated using a six-band effective bond-orbital model. The theoretical results are in excellent agreement with experimental data. Additional important device characteristics such as dark current, spectral response, and absolute responsivity are also presented.