Abstract

Lead telluride (PbTe) and zinc selenide (ZnSe) are Important infrared coating materials. Their spectral characteristics are highly temperature dependence. The temperature coefficient of refractive index of PbTe is about -2.0 × 10^-3/K, that of ZnSe is about 4.8 × 10^-5/K. The central wavelength of the filters composed of PbTe and ZnSe usually shift toward longer wavelength with a decrease in temperature^[1]. Seeley et, al^[2] took advantage of negative temperature coefficient of PbTe to design filters which are relatively temperature-invariant. But for the most cases, it is difficult to manufacture temperature-invariant filters of PbTe and ZnSe.

© 1998 Optical Society of America