An apparatus designed and built to measure the infrared refractive index of an optical material as a function of wavelength and temperature is described. The values obtained for the thermal change in refractive index of a Si–As–Te glass, a Ge–Sb–Se glass, As2S2 glass, and Kodak Irtran 4 are presented. Treatment of these data and literature values for other ir optical materials from a molar refraction standpoint, were used to establish an empirical relationship for predicting unknown ΔN/ΔT°C values of new optical materials. Measured values range from +300 × 10−5/°C for covalent single crystal germanium to −235 × 10−6/°C for ionic polycrystalline KRS–5.
© 1967 Optical Society of AmericaFull Article | PDF Article