Abstract
Employing a sensitive variable angle interference technique the changes in thickness Δl/l and in refractive index Δn/n accompanying the photo‐induced shift of the optical absorption edge toward longer wavelengths were determined in evaporated As2S3 films. The irreversible heat or light‐induced structural change was found to be associated with a decrease in thickness Δl/l=0.011±0.001 and an increase in refractive index Δn/n=0.045±0.005. Changes of l and n associated with the reversible photodarkening effect were found to be less than 0.2 and 0.5 percent, respectively.