Anisotropic structural change induced by sub-bandgap lights in As–S glasses studied by low-frequency Raman scattering

Abstract Changes in low-frequency vibrational modes with illumination of linearly polarized sub-bandgap light have been investigated by monitoring the formation of Bragg gratings in As–S glasses in order to determine photoinduced anisotropic structural rearrangements in a mesoscopic region. We found that the low-frequency vibrational modes show an intriguing change to us, which we suggest is some mesoscopic structural anisotropy due to fragmentary rearrangements induced by polarized sub-bandgap light. The relaxation dynamics of the anisotropic structural rearrangements have also been studied by erasing the Bragg gratings at a temperature lower than the glass transition temperature. We suggest that the thermokinetic structure of the relaxation is low-dimensional and the cooperatively rearranging regions are anisotropic.