Responsivity calibration methods for 365-nm irradiance meters

Two detector-based responsivity calibration methods have been compared at the National Institute of Standards and Technology for ultraviolet irradiance meters in the 365-nm spectral region. Both methods are based on an electrical substitution high-accuracy cryogenic radiometer, but utilize different facilities and transfer standards. One facility is a monochromator-based spectral-power responsivity measuring system utilizing an aperture-scanning method, while the second is a tunable-laser and integrating-sphere source system using a light-trapping silicon transfer detector with a known aperture area. The first reported comparison of these two fundamentally different methods agreed to 1%-2% near the peak and long wavelength side of the bandpass curves which is comparable to their expanded (k=2) uncertainties.