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。

Spectral Irradiance Responsivity Calibration Using Tunable Lasers

The spectral irradiance(radiance)responsivity of the detector is one of the most important parameters.Traditional spectral calibration is realized by using a broadband lamp and monochromator.The newly built facility using a laser and detector to calibrate the spectral responsivity,with the measurement uncertainty dramatically reduced.First,the facility couples tunable laser into an integrating sphere to generate a laser Lambert source.Then using standard trap detectors which can be traced back to cryogenic radiometer and an aperture with the known area,the spectral irradiance responsivity from 400 to 900 nm can be calibrated.The research is focused on four aspects:(1)Since the standard detector is calibrated at separate laser wavelengths by the cryogenic radiometer,the spectral responsivity at any other wavelengths must be interpolated.Compared with the direct measurement method using the spectral responsivity facility,the results show that the quantum efficiency difference using numerical interpolation is less than 0.074% from 400 to 900 nm.(2)In order to reduce the influence due to the laser power drift,the integrated charge method and a monitor detector are used.The charges of the standard detector and the detector under test are measured with the standard deviation of the repetition smaller than 0.1%.(3)The laser power when the standard detector is traced to cryogenic radiometer is totally different from that when the standard detector is used to transfer the spectral irradiance responsivity.Beam addition method is adopted to test the linearity of the detectors.Measurement results show that the nonlinearity correction is less than 0.025% when the current of the detector is varied from 0.2 mA to 3 nA.(4)The responsivity uniformity of the detector is measured to evaluate the uncertainty due to the difference between irradiance mode and power mode.The nonuniformity in an area of 5 mm in diameter is less than 0.03%.The uncertainty of the spectral irradiance responsivity facility from 400 to 900 nm is 0.14%~0.074%(k=1).The spectral irradiance responsivity of the detector measured by the new facility and lamp-monochromator facility is compared.Results show that the two facilities show good agreement from 400 to 900 nm.The difference between the two methods is within the uncertainty of the lamp-monochromator facility.