Photodarkening process in amorphous chalcogenideMeasurements of transient photo-induced optical absorption

We have investigated on photodarkening process in amorphous (a-) As2Se3 and As2S3 by means of photoinduced transient optical absorption measurement. To measure a change of optical absorption in the absorption edge, we used specially designed optical cells which prepared melt-quenched amorphous films with thicknesses of 0.6 μm for a-As2Se3 and 1.5 μm for a-As2S3. From the measurements, we observed accumulation of the photoinduced effect for illumination of repeated pulsed laser and a decay of the photo-induced change after stopping the illumination. We discuss the photodarkening process based on the experimental results.