Density Matrix Treatments Of The Four Level System For Photodarkening Kinetics In Amorphous AS2S3

Recently, photoinduced effects such as photodarkening in amorphous chalcogenide thip ,films have received renewed attention, because of their potential applications in phase conjugation kl), optical holography (2) and other related optical devices.(3) In this work, the density matrix formalism is adapted to explain the complicated time and intensity dependent nonlinear optical absorption changes in amorphous chalcogenide AS2S3 thin films.