Abstract

Recently, we observed beam fanning in photorefractive GaAs. This indicates that self-pumped and double phase conjugation can occur in the material. We report the observation of these two phenomena in liquid encapsulated Czochralski-grown, undoped, semi-insulating GaAs crystals under a dc electric field. A configuration with external mirrors at the opposite side of an incident beam from a Nd:YAG laser was used to observe the self-pumped phase conjugation. The beam reflected back at a different angle via the mirrors was diffracted at the grating formed by the incident beam and its fanned beam and then the diffracted beam was enhanced through a beam coupling process between itself and the reflected beam. In the double phase conjugation experiment, two incoherent beams are incident on opposite sides of the crystal, where they overlap. The interaction between the two beams was initiated by grating formation due to fanning of each beam and then reinforced through generation of a common grating due to the beam coupling process of each beam with its diffracted mate.

© 1989 Optical Society of America