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Linear and non-linear optical properties of thin films from the system As-S-Se♣

J. TASSEVA1,* , R. TODOROV1, K. PETKOV1

Affiliation

  1. Central Laboratory of Photoprocesses “Acad. J. Malinowski”, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 109, 1113 Sofia, Bulgaria

Abstract

Results from a study of the photodarkening effect in amorphous As-S-Se thin films, after exposure to light, are reported. Thin films with thicknesses of 50 to 1000 nm and of different compositions were deposited by thermal vacuum evaporation. Spectrophotometric measurements were carried out in the spectral region 400-2000 nm. An “envelope” method or a triple method (for very thin films) was used to determine the thickness, refractive index and extinction coefficient of the films. The optical constants of the films from the system As-S-Se were found to be thickness-independent. It was observed that an increase in the Se/(S+Se) ratio leads to a linear increase in the refractive index, n, at λ = 1.55 μm, and to a linear decrease in the optical band-gap for the systems with As contents of 28, 33 and 40 at. %. After light exposure, an increase in n and a decrease in the film’s thickness, d were observed. Predictions for the non-linear absorption and index of refraction were made..

Keywords

Thin films, Chalcogenide glasses, Optical properties, Nonlinear refractive index.

Submitted at: Nov. 5, 2008
Accepted at: Sept. 9, 2009

Citation

J. TASSEVA, R. TODOROV, K. PETKOV, Linear and non-linear optical properties of thin films from the system As-S-Se♣, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 9, pp. 1257-1260 (2009)