Abstract

Several samples of photorefractive crystals were used to study pulsed recording of holograms with application of the single-photon and two-photon techniques. A Q-switched Nd:YAG laser with 5 ns pulses was used. The single-photon holographic recording technique was applied to study the rise and decay times of the holograms as well as the lifetime as a function of cw readout with and without preconditioning (single-beam laser pulses, heat, and dc electric field) and strong white light source illumination. The two-photon recording technique was employed to study the phenomenon of optical fixing, the sensitivity of the recording medium, and the enhancement of the diffraction efficiency. Up to 32 single- and two-photon holograms were recorded in one spot in the photorefractive crystal. Definite enhancement of the efficiency by using the two-photon recording technique was found. The lifetime of the holograms was studied as a function of readout time up to 200 h. The holograms were found to decay even with the use of the two-photon recording technique. Diffraction efficiency measurements are also presented for und oped lithium niobate crystals as a function of input recording energies of the fundamental 532 nm recording beams and the 1064 nm bias beam.

© 1992 Optical Society of America