Abstract
Generation of phase conjugate waves in a photorefractive Bi12SiO20 (BSO) crystal is studied with particular attention to the dependence of the efficiency on the spatial frequency of the written grating. The influence of mis-alignment between input beams is also investigated in detail. Since the diffracted output energy is particularly sensitive to the incident angle of the readout beam, alignning of the readout beam to meet Bragg conditionis of critical importance. It is found that diffraction efficiency is proportional to the square of the fringe spacing, ∧2, under the condition of relatively small spacing ∧while it is proportional to ∧-2 when the spacingexceeds a certain value. The result is consistent with “two-level charge transfer model ”proposed by Peltier etal. From the fringe spacing giving a maximum diffraction efficiency, the density of acceptor traps is determined to be 1.3 ×1015cm-3 in the BSO crystal used.
