Mechanism of photoinduced anisotropy in chalcogenide glasses

Structural and optical anisotropies have been investigated in some chalcogenide glasses exposed to illumination of linearly polarized light. X-ray diffraction patterns of illuminated ${\mathrm{As}}_2$ ${\mathrm{S}}_3$ manifest a structural modification at ∼1 A${\mathrm{̊}}^{\mathrm{-}1}$. Photoinduced birefringence in ${\mathrm{As}}_2$ ${\mathrm{S}}_3$ becomes maximal at some temperature, which is higher for illumination with a lower photon energy. The photoinduced birefringence becomes greater in the order of ${\mathrm{As}}_2$ ${\mathrm{Se}}_3$, ${\mathrm{As}}_2$ ${\mathrm{S}}_3$, and Se, which is the same with the order of the natural birefringence in the corresponding crystals. These observations suggest that the photoinduced anisotropy arises from orientation of quasicrystalline clusters. The model is compared with photoinduced anisotropies observed in other materials. © 1996 The American Physical Society.