Comparison of QWIP to HgCdTe detectors for gas imaging

This paper discusses the performance difference of two long-wave (8 to 12 microns) cooled infrared focal plane arrays applied to spectral imaging, one using a HgCdTe detector array and the other using a QWIP detector array. QWIP detectors tend to have a much narrower spectral response than HgCdTe detectors, therefore applications can be limited. For applications for the detection of specific gases, such that the signature of the gas absorption is within the narrower band, the QWIP can be a viable alternative to HgCdTe detectors. Such is the case for detection of sulfurhexafluoride (SF6). In this paper we compare the performance of two different imaging spectrometers where one has a cooled HgCeTe detector array and the other has a cooled QWIP detector array. The gases used in this comparison were sulfurhexafluoride (SF6), 1,1- difloroethane, and 1,1,3 trichloroethane. Figures of merit that will be compared are the noise equivalent spectral radiance (NESR), and visibility. Both detectors have 340 x 256 pixel elements in the array. A paper written comparing HgCdTe and QWIP dual band detectors by Arnold Goldberg et. al. discussed the difference between the two detector materials. To our knowledge, a comparison of a broadband (HgCdTe) and narrow band (QWIP) detector as applied to spectral imaging of gases has never been done before.