Thick holograms in photochromic materials

Thick hologram storage in recently developed CaF(2) and SrTiO(3) photochromic crystals has been demonstrated and studied. It was found that a 2-mW laser at 6328 A yielded good holograms with exposure times of 2-30 see depending on the particular photochromic crystal considered. In the case of CaF(2) crystals, the angular sensitivity of the thick hologram image intensity was found to be in good agreement with theoretical predictions; in SrTiO(3) crystals, angular sensitivity measurements were used to determine the effective hologram thickness. Desirable improvements in photochromic materials for thick hologram storage are suggested.