Evaluation of optical radiation detectors in the range from 0.8 μm to 20 μm at the NIST infrared spectral calibration facility

Analysis of multiple factors affecting the uncertainty of the absolute spectral responsivity of optical radiation detectors is presented. This includes both the validation of the radiometric scale of the infrared reference detectors and the scale transfer process to the unit under test. Reference detectors include a low NEP pyroelectric detector, an InSb detector, and a sphere-input extended InGaAs detector. While all three types of reference detectors were calibrated independently, less than 0.5 % mismatch of spectral responsivities was observed in the spectrally overlapping regions. We provide a performance evaluation of the NIST IR Detector Calibration Facility, which was designed for testing optical radiation detectors in both radiant power and irradiance measurement modes. This facility utilizes a high throughput monochromator with interchangeable diffraction gratings. Depending on the spectral range, a blackbody at 1100 degrees C, or a quartz halogen lamp with about a 10(-4) long-term relative output variation was used as a radiation source. In order to minimize the uncertainty budget for calibration data, specific attention was given to the profile of the incident beam, the precise positioning of detectors, and the influence of atmospheric absorption. In addition to the spectral responsivity calibration of detectors, the facility allows precise mapping of detector active area for spatial non-uniformity of response. Typical calibration uncertainties that can be achieved are about 1 % and 2.5 % (k=2) in the radiant power and irradiance modes, respectively. Examples for responsivity calibrations of different detectors are presented.