Optical constants of tin selenide single crystals in the transparency region

(Received 5 November 1990, revised 29 January 1991, accepted 20 February 1991)

Abstract
The transmittance, T, and reflectance, R, of single crystals of SnSe were measured at normal incidence. The refractive index, n, was measured by the prism method in the transparency region. Measurements were performed at room temperature using plane-polarised light with the plane of polarisation parallel to either the a- or b-crystallographic axis, both of which lie in the plane of cleavage. The extinction coefficient k was calculated from the absorption coefficient. The real and imaginary parts of the complex dielectric constant ( ) as well as the reflectance and its phase change ( ) were calculated from the values of n and k. It was shown that SnSe single crystals exhibit birefringence. Assuming that SnSe binding is partly ionic and partly covalent, the optical constants were satisfactorily fitted to the model of single effective oscillator.