FILTERS FOR THE FAR INFRARED REGION

Abstract

“Reststrahlen reflectivities of several specimens of alkali halides and other crystals, which are used as reflection-type filters, were measured or remeasured in detail in the far-infrared region. Polyethylene films having finely divided materials imbedded, have strong absorptions at their lattice-vibration wavelengths, mostly in the far-infrared region. The materials in the polyethylene included sullides and oxides of cadmium, zinc and other metals. The transmission increases rapidly at the longer wave side. It is, therefore, possible to make transmission filters which absorb fairly broad wavelength intervals, and to vary the center and the breadth of these intervals by changing the mixtures of the powders. Data for both types of filters will be presented.”