Nonvolatile holographic storage in photorefractive lithium tantalate crystals with laser pulses

Nonvolatile holograms are recorded in photorefractive LiTaO3:Fe with laser pulses by use of two-step excitation. Ultraviolet laser pulses (wavelength lambda = 355 nm) yield a strong increase of absorption las much as 600 m(-1 ) at lambda = 633 nm) and sensitize the crystals for subsequent infrared (l ambda = 1064 nm) holographic recording. Refractive-index changes of as much as 1.6 x 10(-4) are achieved for intensities of the infrared light of 10(1 1) W/m(2). The saturation values are proportional to the concentration of F e3+ ions. Nondestructive readout with infrared light is possible, and the h olograms remain erasable for ultraviolet light. Typical time constants of r ecording and erasure are 0.5 mu s for intensities of the ultraviolet light of 1011 W/m2 The results can be explained with a two-level charge-transport model. (C) 1999 Optical Society of America [S0740-3224(99)03509-2].