Mid-infrared trap detector technology based on cryogenic integrating sphere

To meet the requirements of mid-wave infrared radiation measurement and calibration, the micro integrating sphere and mid-infrared detector were integrated in cryogenic environment. Several samples used to make the inner cavity surface of the integrating sphere were verified and compared. Through the measurement of broad-spectrum reflectivity, characteristic spectrum reflectivity, bidirectional reflectance distribution function (BRDF), laser confocal microscope, scanning electron microscope (SEM) and other micro-surface morphologies, the inner cavity surface fabrication process suitable for making the mid-infrared integrating sphere was obtained. The BRDF test results show that it is close to the Lambert reflection surface. The spectral and electrical properties of the integrating sphere detector sample were tested. The spectral band of the sample after surface roughening treatment and evaporation of metal reflection film has good adaptability, the light intensity attenuation ratio is 0.067 4, and the reflectivity of the inner cavity wall of integrating sphere is 96.4% by calculation. At the same time, the introduction of the cryogenic integrating sphere reduces the noise of the detector chip from 3.5×10⁻¹² A·Hz^−1/2 to 1.0×10⁻¹² A·Hz^−1/2.