Measurements of the thermal expansion of six optical materials, from room temperature to 250°C

Abstract
Coefficients of linear thermal expansion are reported in the range from room temperature to 250°C for six optical materials: Polytran potassium chloride and Polytran calcium fluoride—Harshaw; chemical-vapor-deposited (CVD) zinc selenide and zinc sulfide—Raytheon; single-crystal germanium—Eagle-Picher; and lithium niobate—Harshaw. For the last named, an anisotropic crystal, thermal expansion was measured both parallel and perpendicular to the c axis. Curves are given to illustrate the expansion behavior of the materials over the 60–500-K range.