Photoinduced anisotropy in photobleached Ge-As-S films

Linear optical dichroism and birefringence induced by linearly polarized light were studied in the photobleached optically isotropic three-component Ge_xAs_40-xS₆₀ films. The anisotropy can be erased by nonpolarized or circularly polarized light. Multiple reorientation under the action of linearly polarized light with orthogonal orientation of the electrical vector was investigated. The anisotropy relaxes gradually in the dark with a large time constant. The sign of dichroism was the same as in the binary As-Se and As-S photodarkened chalcogenide films. Therefore, the inducing polarized light always decreases the absorption of the light polarized parallel to itself. Photodarkening instead of photobleaching was observed in annealed films. Annealing resulted also in a strong decrease of photoinduced anisotropy that is different from the behaviour of binary chalcogenide films.