Realization of the spectral responsivity scale based on an absolute cryogenic radiometer

We present the concept of and the procedure for realizing the primary scale of the spectral responsivity based on an absolute cryogenic radiometer at the Korea Research Institute of Standards and Science (KRISS). A detailed error and uncertainty analysis is performed by calibrating the standard detectors in the wavelength range from 300 nm to 1000 nm. The relative expanded uncertainty of the spectral responsivity calibration for a Si trap detector is 0.06% at 632.8 nm and 0.4% for other wavelengths (k = 2). The calibration results are validated by comparing with the results from a theoretical model of quantum efficiency for a transmission-type trap detector.