Absolute cryogenic radiometer for high accuracy optical radiant power measurement in a wide spectral range

An absolute cryogenic radiometer(ACR) with a detachable optical window was designed and built for high accuracy optical radiant power measurement and photodetector spectral responsivity calibration. The ACR receiver is an electroplated pure copper cavity with a 50-μm-thick wall and inner surface coated with a specular black polymer material mixed with highly dispersible carbon nanotubes. The absorptivity of the cavity receivers was evaluated to be ≥0.9999 in the 250 nm–16 μm wavelength range and ≥0.99995 in 500 nm–16 μm. The cavity receiver works at the temperature of ～5.2 K with nanowatt-level noise-equivalent power. The relative standard uncertainty is 0.041% for the measurement of ～100 μW optical radiant power(250 nm–16 μm) and 0.015% for～1 m W(500 nm–16 μm).     

基于可调谐飞秒激光的光学特性测量装置

随着激光技术的快速发展,激光光源在光谱辐射和光学特性测量中得到了广泛的应用。与传统的灯光源相比,激光光源具有高功率、宽光谱和极低的波长不确定度等优点。建立了一套基于宽波段可调谐激光光源的光电探测器响应定标装置,其中激光光源的光谱覆盖范围为190 nm～4000 nm,激光脉冲宽度约130 fs,重复频率约80 MHz。为了避免高峰值功率脉冲光对探测器定标的影响并提高测量的线性度,利用光纤的固有特性成功研制了一种可将脉冲光转换成连续光的转换器。同时基于激光光源搭建了一套激光准直和扩束光路,在波长λ=550 nm时得到了非均匀性为0.29%的单色均匀辐射场。该单色均匀辐射场在高精度的探测器定标应用中具有重要的作用,围绕其搭建的定标测量装置在计量领域具有一定的参考价值。