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Ultrahigh Sensitivity Detection System for Far Infrared Spectrophotometers

Volume 27, Number 2 (April 1973) Page 135-136

Poteet, W.M.; Feltham, R.D.

The problems of detection in far infrared grating spectrophotometers can generally be related to several factors: (1) low intensity of available radiation from the source, (2) energy loss due to the filters which are necessary for blocking of unwanted radiation, (3) only a narrow band of energy (the resolution width) available to the detector in a given time increment, (4) inefficiencies in the optical train, and (5) detector characteristics such as sensitivity to incident radiation and inherent noise fluctuations. Some of these problems can be solved in part by careful design of filters and optics. However, even in the case of a nearly perfect optical train the detector sensitivity becomes the limiting factor, and large improvements can be made only by cooling the detector to low temperatures and reducing the background radiation seen by the detector. The low temperature germanium bolometer detector developed by Low1 is several hundred to several thousand time more sensitive than uncooled detectors, depending on the incident background level, and, properly coupled to the spectrophotometer optical train, offers the possibility of greatly enhancing the performance of far infrared instruments.