Sensitive infrared working-standard detectors with large active area are needed to extend the signal dynamic range of the National Institute of Standards and Technology (NIST) pyroelectric transfer-standards used for infrared spectral power responsivity calibrations. Increased sensitivity is especially important for irradiance mode responsivity measurements. The noise equivalent power (NEP) of the NIST used pyroelectric transfer-standards is about 8 nW/Hz^¿, equal to a D*= 5.5 x 10^7 cm Hz^1/2 / W. A large-area photovoltaic HgCdTe (PV-MCT) detector was custom made for the 2.5 to 11 micrometers wavelength range using a 4-stage thermoelectric cooler. At least an order of magnitude lower NEP was expected than that of the pyroelectric transfer-standards to measure irradiance. The large detector area was produced with multiple p-n junctions. The periodical, multiple-junction structure produced a spatial non-uniformity in the detector response. The PV-MCT radiometer was characterized for spatial non-uniformity of response using different incident beam sizes to evaluate the uncertainty component caused by the spatial non-uniformity. The output voltage noise and also the current and voltage responsivities were evaluated at different signal gains and frequencies. The output voltage noise was decreased and the voltage responsivity was increased to lower the NEP of the radiometer. The uncertainty of the spectral power responsivity measurements was evaluated. It is recommended to use a bootstrap type trans-impedance amplifier along with a cold field-of-view limiter to improve the NEP of the PV-MCT radiometer.
current responsivity, infrared, low-NEP, PV-MCT, output noise, spectral responsivity, voltage responsivity, working standard detector
and Podobedov, V.
PV-MCT working standard radiometer, Proceedings of SPIE, Vol. 8355, Baltimore, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=911291
(Accessed October 1, 2023)