Absolute linearity measurements on a PbSe detector in the infrared

The non-linearity characteristics of a commercially available thin-film photoconductive PbSe detection system were experimentally investigated in the infrared using the NPL detector linearity of response characterisation facility. The non-linearity of this detector was shown to be significant, even for relatively low values of radiant power incident on the active area of the detector. The deviation from linearity was shown to be a function of the detector area being illuminated, as well as the wavelength of the incident radiation. The plot of the linearity factor as a function of photon irradiance was shown to exhibit only a weak dependence on the wavelength of radiation illuminating the detector, as well as the area of the spot being illuminated, thus confirming that the linearity factor is a function of photon irradiance. This behaviour is similar to that observed previously in thin-film photoconductive HgCdTe detectors.