Analysis of some optical parameters of the glasses of the system Bi x (As 2 S 3 ) 100‐x

With the aim of characterizing the optical properties of the glasses from the system Bi x (As 2 S 3 ) 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 E g . 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 E e , 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 di‐Domenico dispersion analysis. Among the others, the effective oscillator energy E 0 and the strength parameter of interband optical transitions E d 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 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)