A transmission polarizer for the near infra-red is described, which is small and compact and can be mounted on a spectrometer without alteration of the existing optical system. It employs a pile of self-supporting selenium films, each approximately 4 microns thick. The advantages which such a polarizer possesses over other forms are pointed out, and the factors affecting the design of the pile are briefly discussed. The method of preparing the Se films is described in detail. The percentage polarization, measured by crossing two similar piles, is better than 94 percent with 5 films, and better than 98 percent with 6 films in each pile, over the spectral region 2–14 μ; the maximum transmission is 47 percent of the incident radiation.
No absorption bands of selenium could be detected between 1 and 14 μ using a much thicker layer (52 microns).
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