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Spectral responsivity calibrations of two different types of pyroelectric radiometers have been made in the infrared
region up to 14 μm in power mode using three different calibration facilities at NIST. One pyroelectric radiometer is a
temperature-controlled low noise-equivalent-power (NEP) single-element pyroelectric radiometer with an active area of
5 mm in diameter. The other radiometer is a prototype using the same type of pyroeletric detector with dome-input
optics, which was designed to increase absorptance and to minimize spectral structures to obtain a constant spectral
responsivity. Three calibration facilities at NIST were used to conduct direct and indirect responsivity calibrations tied to
absolute scales in the infrared spectral regime. We report the calibration results for the single-element pyroelectric
radiometer using a new Infrared Spectral Comparator Facility (IRSCF) for direct calibration. Also, a combined method
using the Fourier Transform Infrared Spectrophotometry (FTIS) facility and single wavelength laser tie-points are
described to calibrated standard detectors with an indirect approach. For the dome-input pyroelectric radiometer, the
results obtained from another direct calibration method using a circular variable filter (CVF) spectrometer and the FTIS
are also presented. The inter-comparison of different calibration methods enables us to improve the responsivity
uncertainty performed by the different facilities. For both radiometers, consistent results of the spectral power
responsivity have been obtained applying different methods from 1.5 μm to 14 μm with responsivity uncertainties
between 1 % and 2 % (k = 2). Relevant characterization results, such as spatial uniformity, linearity, and angular
dependence of responsivity, are shown. Validation of the spectral responsivity calibrations, uncertainty sources, and
improvements for each method will also be discussed.
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