To meet the growing need for calibrated detector at long-infrared wavelengths, we are reporting on a laser-based absolute spectral responsivity scale of the detector in the long-infrared spectral region. The high-accuracy cryogenic radiometer (HACR) is a cryogenic electrical substitution radiometer that serves as a primary standard for optical power measurements. We measured the transfer standard HgCdTe/sphere detectors at 9.28μm, 9.62μm, 10.26μm and 10.60μm, respectively. The experimental results show that the extended uncertainty of optical power measurement was less than 0.30%～0.42% (k = 2); The extended uncertainty of the absolute spectral responsivity measurement has been analyzed to be 0.80%～1.02% (k = 2).
The detection efficiency calibration of single-photon avalanche detectors is presented. The detection efficiency is determined from the measurement of the photon count rate and incoming photon flux traceable to reference standard detectors, and corrected by afterpulse probability and dead time. We describe the measurement facilities and the reference standard detectors used, as well as the traceability chain of the measurements to the primary standard detector. As an example, the measurement uncertainty components are determined and analyzed in detail and the obtained combined standard measurement uncertainty is <0.5% at 633nm and 1550nm.
Cryogenic radiometer is considered as the international benchmark for optical power measurement, which requires the core light radiation receiving device (cavity) has high absorption coefficient over 0.9999 at presented. In this paper, we have developed a new cavity are made of oxygen-free high-conductivity copper (OFHC) cylinder and coated with nickel-phosphorus (NiP) black paint. The cavity absorptance has been experimentally evaluated at different black paints and different structures. The result shows that the inclined bottom cylindrical cavity blackened with nickel-phosphorus black paint achieves an absorptance up to 0.9999964±0.000005; The most significant improvements in uncertainty arise from the enhanced characteristics of the cryogenic radiometer including its higher cavity absorptance and reduced non-equivalence effects.