Holographic recording in amorphous As2S3 films at 633 nm

Holographic grating recording with focused (light intensity I = 14–124 W/cm2) and unfocused (I = 0.50–0.78 W/cm2) 633 nm He–Ne laser sub-bandgap light in non-annealed and annealed a-As2S3 films has been experimentally studied. The focused light recording is found to be much more efficient (diffraction efficiency up to 14.9%, specific recording energy down to 216 J/(cm2 %)) than the unfocused light recording (0.11%, 72 400 J/(cm2 %)). Some other properties are also different. The hologram lifetime of more than two years and positive refractive index changes take place in the case of focused recording versus two days and negative refractive index changes for unfocused recording. The absence of measureable photoinduced thickness changes and a slight photobleaching are common properties. The focused light recording is explained by the photostimulated relaxational structural changes (RSC) accompanied by the photoinduced generation and recharging of D-centers. The unfocused light recording is explained by the photorientation of D-centers with some contribution of RSC.