Analysis of some optical parameters of the glasses of the system Bix(As2S3)100-x

Abstract

With the aim of characterizing the optical properties of the glasses from the system Bix(As2S3)100-x, for x=0.5, 2 and 4 at.% Bi, their absorption coefficients and index of refraction were measured. The extrapolation of the linear parts of the absorption coefficient dispersion curve for the different sample thicknesses enabled the determination of the optical band gap Eg. Also, in view of the range of the values of the absorption coefficients for all three glasses, it was possible to determine the Urbach slope Ee, the width of the tails in the localized states of the optical gap.The results of the refractive index measurement were treated using the Wemple diDomenico dispersion analysis. Among the others, the effective oscillator energy E0 and the strength parameter of interband optical transitions Ed were determined, the latter being of special importance as it establishes the link with the other physical parameters of the material. In this way, it was possible to estimate the coordination number in the investigated glasses, which enabled the derivation of certain conclusions about the lattice modification caused by introducing Bi into the arsenic-sulfide matrix.