Infrared - detector and infra-red controlled device

摘要

An infrared detector for operation at a cryogenic temperature has a photoconductive element (10) supported by a mounting substrate (26) which is formed as a sandwich comprising at least two superimposed thin layers (27, 28) of a material of high thermal diffusivity separated by a layer (29) of bonding cement which is sufficiently thin to leave the thermal properties of the substrate (27) substantially unaffected. The substrate (27) is very rapidly cooled by suitable cooling means (20), such as an open cycle Joule-Thompson mini-cooler (17), but its sandwich construction (27, 28, 29) reduces the incidence of electrical noise induced in the photoconductive element (10) thereby enabling increased performance. The element (10) may be epitaxially grown on a gallium arsenide layer (27).