Accumulation and decay processes in photodarkening of amorphous chalcogenide

Accumulation and decay processes in photodarkening of amorphous chalcogenide have been investigated by measuring photoinduced transient optical absorption of amorphous As2Se3 and As2S3. From the measurements, we observed accumulation of the photoinduced effect for an illumination of repeated pulsed laser. After stopping the illumination, a decay of the photoinduced change and the saturation of the decay were observed, which is related to transient photodarkening and durable photodarkening, respectively. The difference of the two types of photodarkening clearly observed in the repeated experimental procedure composed of illuminated and non-illuminated period and the temperature dependence. From the measurements of the photoinduced absorption spectra, a peak located at the energy higher than the optical gap was observed in the spectra during and after stopping illumination.