ROOM-TEMPERATURE HOLOGRAPHIC GRATING RECORDING IN CDF2-GA

We demonstrate that semiconducting CdF2 crystals doped with gallium pr ovide an efficient medium for optical storage of information in static and dynamic regimes in a temperature range close to 300 K. Ga is a bi stable center in CdF2 crystals. Illumination by visible and UV light b elow 500 nm causes phototransformation of these centers from a deep-lo calized to a shallow-hydrogenic state. They are separated by a vibroni c barrier that causes metastability below 250 K. The phototransformati on changes the local polarizability, and thus, the local refractive co efficient. This, in turn, allows writing a phase hologram with a diffr action efficiency and decay time being temperature dependent with the activation energy E-act=0.65+/-0.1 eV. A spontaneous decay of the grat ing is caused by a thermal recovery of the Ga impurity from the metast able hydrogenic state to the localized ground state. The writing is a local process. (C) 1997 American Institute of Physics.