溯源至低温辐射计的硅陷阱探测器紫外波段绝对光谱响应度测量（英文）

介绍了溯源至低温辐射计的紫外绝对光谱响应度测量装置,对硅陷阱探测器在三个激光波长点进行了绝对光谱响应度校准实验.测量了硅陷阱探测器的空间均匀性和非线性系数,分析了影响测量准确度的各不确定度分量.实验表明:硅陷阱探测器在紫外波段266、325、379nm三个激光波长点处的绝对光谱响应度测量扩展不确定度分别为0.19%、0.14%、0.11%,可作为紫外波段光辐射功率基准保持和传递的标准探测器,用于提高紫外波段光谱辐射度的校准能力.     

硅陷阱探测器在350—1064 nm波段的绝对光谱响应度定标

介绍了利用钛宝石可调谐激光器、倍频器和单波长激光器作为光源,在24个波长分立点定标了三个硅陷阱探测器的绝对光谱响应度,解决了红外激光的精确定位与调整、窗口透过率模拟定标等关键技术.结果显示：在激光波长为412—800nm时,三个陷阱探测器定标的不确定度约低于0.05％;当激光波长大于800nm以及低于355nm时,获得的陷阱探测器的定标不确定度约低于0.065％.硅陷阱探测器可以作为空间各类遥感器在350—1064nm波段定标的传递标准探测器. 关键词： 陷阱探测器 低温辐射计 光谱响应度 辐射定标     

硅陷阱探测器绝对光谱响应率校准实验研究

以Ar^＋Kr^＋激光器、He—Ne激光器和半导体泵浦激光器作为光源,利用激光稳功率装置以及闭环机械制冷型低温辐射计,校准了硅陷阱探测器的绝对光谱响应率。在硅探测器的光谱响应范围400-1100nm内,选择476．1nm、488nm、514．7nm、521nm、568nm、632．8nm、647．1nm、1064nm共8条谱线进行了实验研究。实验数据表明,绝对光谱响应率的测量不确定度为可见光波段优于0．02％,1064nm波长点优于0．03％。     

可见-近红外(488～944 nm)基于低温辐射计的高精度光辐射绝对定标研究

报道了可见-近红外波段(488～944nm)基于低温辐射计的光谱辐射功率定标和标准传递实验和研究,并对测量结果的各个不确定因素进行了测量和分析。首先低温辐射计采用电替代方法测量单个波长激光绝对光功率,测量不确定度低于0．016％。然后利用低温辐射计定标作为标准传递探测器的硅陷阱探测器,从而建立可见-近红外波段陷阱探测器的绝对光谱响应率标准,其不确定度小于0．028％。结果证明了在此波段以探测器为基础建立和传递高精度光辐射标准的合理性和可行性。     

低温辐射计紫外探测器光谱响应度测试技术研究北大核心CSCD

通过研制真空多光路切换组件,结合Y型真空比较通道、探测器真空舱,在保证超高真空环境的前提下,实现激光、紫外连续可调单色光以及真空紫外单色光3个光路的快速切换,从而以低温辐射计为基准,以紫外增强硅陷阱探测器为传递标准,实现波长115 nm~400 nm紫外探测器绝对光谱响应度的测量,实验验证绝对光谱响应度测量不确定度在115 nm~230 nm可达到0.8%~1.5%(k=2),在230 nm~400 nm可达到0.5%~1.0%(k=2)。     

不确定度优于0.035%的绝对光谱响应率标准探测器

讨论了由无窗硅光电二极管构成的反射式陷阱探测器的设计方案和工作原理 ,通过实验测试证明它具有良好的线性、空间响应均匀性、偏振非敏感性和稳定性。在可见波段的7个激光波长上（488nm-786nm),通过低温辐射计标定了陷阱探测器的绝对光谱响应率,不确定度小于0.035%,比现有的标准辐射源的精度提高了约2个量级,证明其可以作为高精度的绝对光谱响应率标准探测器。     

绝对辐射计溯源至低温辐射计实验测试

开展了绝对辐射计溯源至低温辐射计的计量技术研究。选用激光作为光源,采用光斑非全覆盖绝对辐射计接收面的辐射功率模式进行校准实验。利用溯源至低温辐射计的陷阱探测器作为标准器定标激光器功率,然后通过替代法将量值传递至绝对辐射计。通过绝对辐射计光阑面积校准,实现激光功率与绝对辐射计测量辐照度的转化。通过对陷阱探测器的校准、绝对辐射计锥腔不同位置空间响应均匀性、锥腔的波长选择性等特性的分析,对实验所用绝对辐射计校准不确定度进行了详细评估,得到的校准不确定度为0.86%(包含因子k=2)。     

基于可调谐激光的光谱辐射照度响应度定标

探测器的光谱辐射照(亮)度响应度是辐射定标中最重要的参数之一。传统的光谱辐射定标采用宽谱段光源和单色仪装置测量,新建的激光辐射测量装置采用激光和探测器测量,可以大大降低测量的不确定度。该装置首先将可调谐激光耦合进入积分球生成均匀的朗伯体单色光源,然后采用低温辐射计量传的标准陷阱探测器和面积已知的光阑,进行400～900 nm探测器的光谱辐射照度响应度标定。研究主要集中在四个方面：(1) 低温辐射计仅在某些分立激光波长定标标准探测器,其他激光波长下的光谱响应度必须进行插值,通过对比光谱响应度直接测量方法推导的陷阱探测器量子吸收效率,可以计算插值在其他波长带来的光谱响应度偏差,结果表明400～900 nm数据插值算法的总体偏差小于0.074%;(2) 实验采用电荷积分法测量标准探测器和被测探测器的电荷信号,并采用监视探测器消除激光功率起伏以降低激光功率稳定性的影响,测量重复性优于0.1%;(3) 针对标准探测器在向低温辐射计溯源和进行光谱辐射照度响应度量传时的激光功率差异,采用激光双光路叠加法测量探测器不同波长下的非线性系数,分析标准探测器光谱非线性带来的测量不确定度,在450,632.8和850 nm波长下,当探测器电流从0.2 mA变到3 nA时的非线性修正小于1.000 25;(4) 针对标准探测器定标时的功率模式和量传时的辐射照度模式差异,采用二维电控位移平台测量探测器的均匀性并进行修正,测量得到的标准探测器中心直径5 mm的非均匀性小于0.03%。最终采用可调谐激光辐射照度响应度测量装置,可以实现400～900 nm辐射照度响应度测量不确定度0.14%～0.074%(k=1)。实验对比了激光辐照度响应度装置和标准灯-单色仪装置两种方法测量的探测器的光谱辐射照度响应度。测量结果表明两种装置在400～900 nm的响应度标定近似等价,测量偏差全部位于标准灯-单色仪装置的测量不确定度范围内, 验证了激光辐照度响应度测量装置的实用性。     

基于低温辐射计的InGaAs陷阱探测器高精度光辐射定标研究

介绍了以InGaAs陷阱探测器作为传递探测器,基于低温辐射计的高精度光辐射定标和标准传递实验与研究。在红外(944-1589nm)三个波长初步给出了InGaAs陷阱探测器绝对光谱响应率定标结果。InGaAs陷阱探测器绝对光谱响应率的联合不确定最大为0.655%,最小为0.026%。     

用卤钨灯对激光诱导击穿光谱探测系统进行绝对效率标定（英文）

基于辐射度学理论搭建了用于激光诱导击穿光谱探测系统的绝对效率标定装置.用卤钨灯配备紫外玻璃滤光片和熔融石英漫射片作为标定的标准光源,标定了配备Czerny-Turner型紫外波段光谱仪的激光诱导等离子体光谱探测系统.测得了系统在310~385nm波长范围内的绝对光谱响应,不确定度小于7%(在标准偏差为2的条件下).绝对效率标定可为激光诱导击穿光谱探测系统硬件评估提供一种手段.     

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.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

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.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.