Sheet Infrared Transmission Polarizers

The production and properties of sheet infrared transmission polarizers of the parallel wire-grating type are discussed. These polarizers are produced by evaporation of a metal conductor on one side of the grooves of an infrared-transmitting plastic film echelette diffraction grating and were first described by Bird and Parrish in 1960. The principal advance in technique given here lies in the use of a commercially available plastic film grating (which is the critical component) and in the fabrication of film gratings of polyethylene which have fewer absorption bands. The degree of polarization is above 98% and the transmission is above 70% in most of the spectral region between 50 cm−1 and 600 cm−1. In the region from 600 cm−1 to 5000 cm−1, the degree of polarization is above 95%, but some plastic absorption bands limit the coverage.