Pyroelectric and other infrared detection devices with thin films

Abstract

An infrared detection device, e.g. for the 8 to 14 micrometer waveband, comprises a Langmuir-Blodgett or other very thin film (10) having pyroelectric or other temperature-dependent characteristics. At least one detector element having opposite electrical conductors (21 and 22) is formed in the film (10). The film (10) which may have a support layer (15) is mostly free of contact with a mount arrangement (25) which supports the film (10) in a very low thermally-conductive manner. In accordance with the present invention, the film (10) is very thin, but very efficient absorption of the radiation (31) is obtained in the following manner: the facing surface (26) of the mount arrangement (25) is reflective for the radiation (31); the sum of the optical thicknesses of the film (10), of any support layer (15) and (d) of a gap (28) forming the multiple layer detector-element structure along the radiation path to the reflector (26) is approximately one quarter of a selected wavelength (e.g. 9.6 micrometers) in the range to be detected; and the conductors (21 and 22) each comprise a resistive layer providing a sufficient resistance per square (Z1 and Z2, e.g. of twice the characteristic impedance of free space) as to absorb a substantial proportion of the incident radiation (31) and reflected radiation (32) in the wavelength range. Spaced supporting elements (252) below the film (10) can support the film (10) over the reflector (26) with a well-defined small gap (28) and carry an electrical connection to the second conductor(s) (22) below the film.