Intensity-dependent transient photodarkening in visible and far infrared absorption spectra of As50Se50 thin film

We report intensity-dependent transient photodarkening (TPD) in As50Se50 thin film when illuminated with sub-bandgap light of wavelength 671 nm. TPD is always accompanied by concurrent changes in the far infrared absorption spectrum and points out the structural units associated with such changes. Strikingly TPD and its kinetics show an exponential dependence on the pump beam intensity and we foresee that light intensity can be used as an effective tool to control such processes.