Ionic and electronic dark decay of holograms in LiNbO3 : Fe crystals

The lifetimes of nonfixed holograms in LiNbO3:Fe crystals with doping level s of 0.05, 0.138, and 0.25 wt % Fe2O3 have been measured in the temperature range from 30 to 180 degreesC. The time constants of the dark decay of hol ograms stored in crystals with doping levels of 0.05 and 0.25 wt % Fe2O3 ob ey an Arrhenius-type dependence on absolute temperature T, but yield two ac tivation energies: 1.0 and 0.28 eV, respectively. For these crystals, two d ifferent dark decay mechanisms are prevailing, one of which is identified a s proton compensation and the other is due to electron tunneling between si tes of Fe2+ and Fe3+. The dark decay of holograms stored in crystals with t he doping level of 0.138 wt % Fe2O3 is the result of a combination of both effects. (C) 2001 American Institute of Physics.