Photoinduced anisotropy in vitreousAs2S3:mA reflectance-difference study

Results of the study of photoinduced anisotropy in a model chalcogenide glass ${\mathrm{As}}_2$ ${\mathrm{S}}_3$ using reflectance-difference spectroscopy are presented. We find that anisotropy can be induced in the energy range much exceeding the energy of the photons of the exciting light and that not only defects but also main covalent bonds of the glass are reoriented by linearly polarized light. We further demonstrate that the sign of the photoinduced anisotropy, especially at higher energies, strongly depends on the photon energy of the exciting light. The observed difference is explained by photoinduced change in the bonds topology involving a conversion between bonding and nonbonding electrons. Strong differences are observed between bulk glass and thin films which are shown to be caused by interference effects.