EXTENSION OF THE NIST SPECTRAL POWER AND IRRADIANCE RESPONSIVITY CALIBRATIONS TO 2.5 MICROMETERS

A spectral comparator facility for spectral power and irradiance responsivity calibrations in the 950 nm to 2500 nm wavelength range has been developed at NIST for routine and low-uncertainty calibrations. A regular-monochromator based source was used instead of tunable laser-based sources to make the spectral scans fast, while an integrating sphere with a few lasers at fixed wavelengths is used as an irradiance source. Sphere-input extended-InGaAs and low noise-equivalent-power (NEP) pyroelectric transfer standard radiometers have been developed to realize the spectral power and irradiance responsivity scales. Extended-InGaAs working-standard radiometers have also been developed to hold and to disseminate the new scales. Calibration procedures for both the scale realizations and transfer have been developed. Expanded uncertainties of less than 1.5 % (k=2) were performed for the extended responsivity scales.