Calculation and experiment on diffraction efficiency of pulse beam operating four-wave mixing in photorefractive crystal.

Four-wave mixing using the photorefractive crystal is one of the methods used to generate the phase-conjugate optical beam. This paper considers the case where the pulse beam is used for the backward pump and calculates the diffraction efficiency. The coupled wave equation that describes the four-wave mixing process using the photorefractive crystal is analyzed numerically by Euler's method, and the transient characteristics of the diffraction efficiency are calculated. The following situation is considered. A crystal reaches the steady state, being radiated by two beams, i.e., the forward pump beam and the probe beam, and only the transmission diffraction grating is produced. Then, the continuous beam or the pulse beam is incident to the crystal as the backward pump. The transient characteristics of the diffraction efficiency are compared and it is shown that the diffraction efficiency is greatly improved by using the pulse beam. In order to verify the results of this study, a BaTiO3 crystal is used as the photorefractive crystal, and the phase conjugate beam generation experiment is tried. The measured waveform for the case where the continuous beam and the pulse beam are incident as the backward pump is shown and improvement of the diffraction efficiency is demonstrated by pulsed beam. © 1998 Scripta Technica. Electron Comm Jpn, Pt 2, 80(9): 10–18, 1997 [ABSTRACT FROM AUTHOR]