Use of bistable centers in CdF2 in holographic recording

We show that bistability and metastability of In and Ga impurities in CdF2 crystals can be efficiently used in writing volume holographic gratings. Phototransformation of these impurities from the localized to the hydrogenic state leads to a large change of the local polarizability of the host, and thus a significant change of the refractive index (more than 10(-4) at 500 nm wavelength, and for the concentration of phototransformed centers of about 10(18) cm(-3) only). While CdF2: In can be used at low temperatures (below 150K), CdF2: Ga crystals are suitable for room temperature recording. The magnitude of the refractive index changes related to a photoinduced metastable deep-shallow transition places these crystals among most efficient recording media.