一种新型电校准光辐射探测器特性的研究

对一种新型电校准辐射计的面响应不均匀性、线性和绝对响应度等特性进行了研究。在０．７～７５０μＷ范围内测得其线性度优于０．５％。面响应不均匀性的测量是利用小的激光光斑在探测器的灵敏面进行二维扫描。在探测器的主要灵敏面内,相对响应度与到探测器中心的距离表现为二次曲面关系。本对不同光斑大小、光束横截面上不同功率分布以及光斑入射到探测器表面的不同位置引起的测量误差进行了分析和研究。给出了是否需要修正的判据和需要修正时所应采用的修正方法,这种方法也适用于其它类型的电校准辐射计,利用该修正方法可以显降低测量不确定度。实验考查了面响应不均匀性的影响,实验结果证明了修正方法的正确性。     

发光二极管(LED)国家光度标准的研究

用变角光度测量装置建立LED光度标准的方法,LED光强度测量不确定度为3.9%,LED光通量测量不确定度为4.8%.     

陷阱探测器面响应均匀性的测量

对陷阱探测器的面响应均匀性进行了测量。在主要灵敏面内 ,面响应均匀性测量结果的重复性达到 4×10 -5。给出了对 S1337、S12 2 7等 4种不同硅光电二极管构成的陷阱探测器的面响应均匀性的测量结果。测量结果表明 ,不同类型探测器之间面响应不均匀性存在显著差异 ,其中 S1337构成的陷阱探测器的面响应均匀性最好。正确选择合适类型探测器 ,对保持和传递低温辐射计达到的很低的不确定度非常重要。     

发光二极管（LED）国家光度标准的研究

用变角光度测量装置建立LED光度标准的方法，LED光强度测量不确定度为3．9％，LED光能量测量不确定度为4．8％。     

用全滤色片法进行光探测器相对光谱响应的修正

色玻璃全滤色片法是进行光探测器相对光谱响应修正的常用方法。本文讨论该法所用的滤光器在平行光垂直照明和漫射光照明两种情形下的最优设计问题,给出滤光器在漫射光照明下探头相对光谱响应的计算模型。实验结果与理论计算符合得很好。     

激光散斑去除效果定量分析

自行研制的外部导入宽可调谐激光的积分球光源中为了提高光辐射场的均匀性和稳定性,采用球内旋转漫射板方法去除激光相干性产生的散斑.为了定量评价退相干效果和漫射板旋转速率之间的关系,使用响应度均匀性经过校正的CCD对积分球出口成像,计算不同积分时间,不同转速条件下的散斑对比度.实验结果表明,漫射板只需在很低的速率下旋转就能完全去除散斑噪声.漫射板不旋转时,散斑对比度约为30%;散斑完全去除时,对比度降为5%.     

线型光束感烟滤光片的校准方法及合理性分析

线型光束感烟滤光片的校准主要包括减光值、正反面误差、均匀性和稳定性。以双光束紫外、可见、近红外分光光度计为测量设备,在800~1 000 nm的范围内测定滤光片的光谱透射比并计算出相应的减光值。结合光源的光谱功率分布和探测器的光谱响应度,分析了滤光片光谱透射比非"中性"对测量结果的影响。提出了以积分法计算减光值,降低测量结果不确定度的方法。     

基于低温辐射计的光探测器响应度基准

基于低温辐射计建立了一系列激光波长上光探测器响应度测量基准。进行了基准装置性能的研究,应用光辐射有效加热功率检验方法进行了不确定度评估。在氦氖、氩氪离子以及钛蓝宝石激光器的10个波长上测量了作为标准探测器的陷阱探测器的响应度。在氦氖、氩氪离子激光波长测量结果的不确定度达到0.8×10^-4,在钛蓝宝石激光器达到1.1×10^-4。对标准探测器的面响应均匀性、非线性、偏振响应、角度响应等特性对响应度测量结果的影响进行了研究。     

陷光探测器偏振响应特性的研究

偏振响应特性是反映光探测器质量的重要参数。陷光探测器(陷光二极管)是低温辐射计的传递探测器。中对陷光探测器的偏振响应特性进行了测量研究，并提出了对它的数值表述方法。探测器偏振响应特性的测量结果的不确定度达到0．005％。测量结果表明，不同的反射型陷光探测器的偏振响应特性相差很大，在光辐射测量中不容忽视。     

InP 层对正面及背面入光 PIN 探测器响应度影响研究

InP盖层对光的吸收及入射光在探测器多界面间的多次反射,使InP层对InGaAs/InPPIN探测器的响应度产生了很大的影响。本文测量了正面和背面入光PIN探测器的响应度,并与测量的InP晶片透射率及模拟的透射率进行比较,分析了InP层对正面及背面入光PIN探测器响应度的影响。结果表明,随着InP层厚度的增加,响应度峰与峰的间隔Δλ不断减小,波形越来越密集。所以正面入光探测器的响应度起伏比较明显,且随着InP层厚度的增加,响应度极值对应的波长发生红移。背面入光探测器的响应度非常密集而成为准连续的带状。     

Uncertainty evaluation for the spectroradiometric measurement of the averaged light-emitting diode intensity

An uncertainty evaluation is presented for the spectroradiometric measurement of the averaged LED intensity (ALI), which is a standardized photometric quantity of LEDs introduced by the Commission Internationale de l'Eclairage. Using a spectral irradiance standard lamp as a calibration source for the spectroradiometer, 12 uncertainty components are sorted out and their propagation formulated with correlations between the components taken into account. The procedure of uncertainty evaluation is demonstrated for four LED samples of different colors; red, green, blue, and white. The relative uncertainties of the ALI of the test samples are determined to be in a range from 4.1% to 5.5% (k=2), but most of their dominant uncertainty components turn out to be systematic and correlated. In conclusion, correlations between the uncertainty components critically affect the overall uncertainty of the LED measurement using a spectroradiometer.     

Some Effects of Temporal Coherence on the First Order Statistics of Speckle

Moments and the first order probability density function of the intensity in a speckle pattern are considered as a function of the spectral bandwidth of the incident light. It is shown that the standard deviation of the intensity generally depends on the surface roughness of the diffuser, and on the position of measurement in the far field. Numerical results are given for a diffuser with a Gaussian distribution of surface height limited by a circular aperture. Exact and approximate forms of the probability density function are discussed. The analysis applies when the fluctuations in optical path are greater than the maximum wavelength incident.     

Interpolation of the spectral responsivity of silicon photodetectors in the near ultraviolet

We improve the methods used to interpolate the responsivity of unbiased silicon photodetectors in the near-ultraviolet region. This improvement is achieved by the derivation of an interpolation function for the quantum yield of silicon and by consideration of this function in the interpolation of the internal quantum efficiency of photodiodes. The calculated quantum-yield and spectral-responsivity values are compared with measurement results obtained by the study of a silicon trap detector and with values reported by other research groups. The comparisons show agreement with a standard deviation of 0.4% between our measured and modeled values for both the quantum yield and the spectral responsivity within the wavelength region from 260 to 400 nm. The proposed methods thus extend the predictability of the spectral responsivity of silicon photodetectors to the wavelength region from 260 to 950 nm. Furthermore, an explanation is proposed for the change in the spectral responsivity of silicon photodiodes that is due to UV radiation. In our improved quantum efficiency model the spectral change can be accounted for completely by the adjustment of just one parameter, i.e., the collection efficiency near the SiO(2)/Si interface.     

Graphene–Ruthenium Complex Hybrid Photodetectors with Ultrahigh Photoresponsivity

The maximum responsivity of a pure monolayer graphene‐based photodetector is currently less than 10 mA W^?1 because of small optical absorption and short recombination lifetime. Here, a graphene hybrid photodetector functionalized with a photoactive ruthenium complex that shows an ultrahigh responsivity of ≈1 × 10⁵ A W^?1 and a photoconductive gain of ≈3 × 10⁶ under incident optical intensity of the order of sub‐milliwatts is reported. This responsivity is two orders of magnitude higher than the precedent best performance of graphene‐based photodetectors under a similar incident light intensity. Upon functionalization with a 4‐nm‐thick ruthenium complex, monolayer graphene‐based photodetectors exhibit pronounced n‐type doping effect due to electron transfer via the metal?ligand charge transfer (MLCT) from the ruthenium complex to graphene. The ultrahigh responsivity is attributed to the long lifetime and high mobility of the photoexcited charge carriers. This approach is highly promising for improving the responsivity of graphene‐based photodetectors.     

基于成像球光强测量系统的光学设计

提出一种新的快速测量空间光强分布的方法,完成基于该方法测量系统的光学系统设计,并对光学系统的关键器件进行设计.利用Matlab编程和Solidworks三维建模得到自由曲面反射镜面型,Zemax光学软件设计优化得到双高斯物镜.光线追踪仿真软件LightTools对测量系统进行模拟仿真,验证系统的可行性,并对该构架下测量系统最小角分辨率和动态范围的关键性能指标进行分析.结果表明,设计的基于成像球的测量系统可实现空间光强分布测量.     

Differential spectral responsivity measurement of photovoltaic detectors with a light-emitting-diode-based integrating sphere source

We present an experimental realization of differential spectral responsivity measurement by using a light-emitting diode (LED)-based integrating sphere source. The spectral irradiance responsivity is measured by a Lambertian-like radiation field with a diameter of 40 mm at the peak wavelengths of the 35 selectable LEDs covering a range from 280 to 1550 nm. The systematic errors and uncertainties due to lock-in detection, spatial irradiance distribution, and reflection from the test detector are experimentally corrected or considered. In addition, we implemented a numerical procedure to correct the error due to the broad spectral bandwidth of the LEDs. The overall uncertainty of the DSR measurement is evaluated to be 2.2% (k = 2) for Si detectors. To demonstrate its application, we present the measurement results of two Si photovoltaic detectors at different bias irradiance levels up to 120 mW/cm(2).     

Uniform theory of the Talbot effect with partially coherent light illumination

A uniform formulation for the self-imaging of gratings with any kind of partially coherent illumination is developed in terms of the cross mutual spectral density of the partial coherence theory. The formulation includes the time diffractive intensity distribution and the averaged diffractive intensity distribution at self-imaging distances and can be applied to both continuous and temporal illuminations with any kind of spectra. It is found that the averaged intensity distribution is related only to the intensity spectrum of illumination. The continuous polychromatic illumination and the ultrashort laser pulses with or without frequency chirp are then studied by a numerical stimulation. It is shown that the ultrashort laser pulse and the continuous polychromatic illuminations have similar averaged self-image distributions. Thus the Talbot effect may help in the study of the temporal and spectral characteristics of ultrashort laser pulses. An experiment with an LED is given, as well.     

Determining the irradiance signal from an asymmetric source with directional detectors: application to calibrations of radiometers with diffusers

The energy transfer integral between radiating rectangular and detecting circular parallel plates having nonideal angular characteristics is solved for modeling the distance dependence of the irradiance signal. The equation derived for the irradiance signal, which is called the modified inverse-square law, depends on the position, shape, size, and angular characteristics of the light source and the detector. We apply the new model equation to the calibration of a spectroradiometer to determine accurately the distance offsets, which fix the positions of the effective receiving apertures of diffusers used in the entrance optics of spectroradiometers. Earlier measurement results, e.g., for solar UV irradiance, may include uncorrected effects and can be corrected reliably as diffuser offsets and other correction factors are determined with the modified inverse-square law. Simplifications of the modified inverse-square law for analyzing the distance offsets and the correction factors are studied. Simplified equations for the diffuser offset analysis may be used without losing the accuracy when the cosine response of the diffuser is reasonably good. However, for diffusers whose angular responsivities deviate much from the cosinusoidal angular responsivity, large approximation errors in the diffuser offset values may appear if the angular effects are not properly taken into account.     

Atomically Thin Oxyhalide Solar‐Blind Photodetectors

2D wide‐bandgap semiconductors demonstrate great potential in fabricating solar‐blind ultraviolet (SBUV) photodetectors. However, the low responsivity of 2D solar‐blind photodetectors still limits their practical applications. Here, high‐responsivity solar‐blind photodetectors are achieved based on 2D bismuth oxychloride (BiOCl) flakes. The 2D BiOCl photodetectors exhibit a responsivity up to 35.7 A W^?1 and a specific detectivity of 2.2 × 10¹⁰ Jones under 250 nm illumination with 17.8 µW cm^?2 power density. In particular, the enhanced photodetective performances are demonstrated in BiOCl photodetectors with increasing ambient temperature. Surprisingly, their responsivity can reach 2060 A W^?1 at 450 K under solar‐blind light illumination, maybe owing to the formation of defective BiOCl grains evidenced by in situ transmission electron microscopy. The high responsivity throughout the solar‐blind range indicates that 2D BiOCl is a promising candidate for SBUV detection.     

Low-noise solar-blind photodetectors based on LaAlO3 single crystal with transparent indium-tin-oxide electrode as detection window

The low-noise solar-blind photodetectors of indium-tin-oxide/LaAlO(3)/Ag (ITO/LAO/Ag) have been fabricated based on the properties of LAO bandgap excitation and the transparent conductance of ITO thin film. The ITO thin films are epitaxially grown on LAO wafers as the electrodes and detection windows of the photodetectors. The photodetectors have low noise and excellent electromagnetic shielding. The influence of the thickness of ITO thin films on the responsivity of the photodetectors has been studied. The photocurrent responsivity can reach 10.3 mA/W under the irradiation of 200-220 nm for a photodetector with 5 nm thick ITO film. The noise current is 1 pA order magnitude under the sunlight at midday. The experiment results suggest that ITO/LAO/Ag is one of the promising structures for the solar-blind deep-ultraviolet photodetectors.