OPTICAL MEMORY IN CHALCOGENIDE GLASSES

Some glasses are light-sensitive, being possible candidates for optical memory. Chalcogenide glasses display the highest photoinduced effects among other materials, their photosensitivity does not involve chemical reactions. In spite of the long history of experimental and theoretical studies, there are still no well-accepted models for photoinduced changes in chalcogenide glasses. In the present work it is demonstrated that a simple approach, implying photoinduced local heating, allows one to explain basic features of photoinduced changes in chalcogenide glasses. The model uses the feature that glasses at nanometer scales are inhomogeneous, consisting of nanoregions. The structure of covalent glasses at nanometer scales in a certain sense is similar to the crystalline-like order, which in the case of chalcogenide glasses implies the existence of polarization dichroism of absorption. In the framework of the model, photo-induced changes (both scalar and vector ones) occur in each single act of light absorption. They are related to reconstruction of nanoregions owing to local heating and subsequent quenching. Vector changes (in addition to scalar changes) occur because of selective absorption predominantly in those nanoregions whose maximum absorption axis coincides with the direction of polarization in the light wave.