Optical constants of far infrared materials 3: plastics

Room temperature optical constants of plastic materials have been measured over the 50-350-cm(-1) spectral range. The materials reported include high density polyethylene, TPX, Aclar, Kapton, Surlyn, and Mylar. All except TPX are available in sheet form and exhibit birefringence as a consequence of stretching during the manufacturing process. Only the average of the two sets of optical constants is reported for each material. The refractive index was calculated from the channeled spectrum as observed in reflection from the sample, while the absorption coefficient was determined, in all cases but polyethylene, from a transmission measurement.