Development, applications, and future of infrared upconversion

Infrared upconversion is a technique that converts linearly polarized infrared photons to photons of higher frequency. The technique can be applied advantageously to the detection of IR radiation because the upconverted signal can be detected by photon-counting devices available for the visible spectral region. In addition, unlike presently available IR detectors, an upconversion device can provide sensitivity to IR radiation without the need for cryogenic cooling. Infrared upconversion was first demonstrated in 1961. By 1974, approximately 100% quantum conversion efficiency and a bandwidth of 1.81 microns had been attained. Photometric detection of IR radiation from various astronomical objects had also been demonstrated. Research is presently under way on the application of upconversion to astronomical spectroscopy and to imaging. The major drawback to the upconversion technique is the sheer bulk of the apparatus involved. It is anticipated that this problem can be overcome by applying the developing technology of integrated optics.