Polarization Dependence of Holographic Grating in Chalcogenide Film

Authors investigated the polarization dependence of and the effect of annealing in chalcogenide Se75Ge25 and As40Ge10Se15S35 thin films, with respect to the holographic grating formation. The film was irradiated by light from a linearly polarized He-Ne laser at l=633 nm. The holographic grating period is in the film 1.8 mu m. The diffraction efficiency of Se75Ge25 thin film is 0.011% in the film of 1 mu m thickness and 0.065% in the film of 3 mu m thickness in the S-polarization state. For As40Ge10Se15S35 thin film, the diffraction efficiency is 0.22% as recorded in the P-polarization state. The maximum diffraction efficiency increased, from 0.22% to 0.75%, after annealing the As40Ge10Se15S35 thin film at 200 C. This result seems to indicate that the number of defects diminished by annealing of the thin film increase the directional optical expansion effect, which is due to the optical structure change caused by exposure to optical energy. 12 refs.