We demonstrate experimentally that internal ref lections of a signal and (or) a pump beam allow one to increase beam amplification by two-beam coupling in a long Bi12TiO20 crystal. When fanning is negligible, we achieve an enhancement of the amplification by adjustment of the spatial period of the transformation of the beam’s polarization states with periodic reflections of the beams on the crystal boundaries. For the case of strong fanning the fanned beam is redirected by the reflections on the crystal surface, which allows one to use it as a pump beam, thus increasing net amplification gain.
© 1996 Optical Society of America
A. V. Khomenko, A. García-Weidner, and D. Tentori, "Enhanced beam amplification in a photorefractive Bi12TiO20 crystal by internal reflections," Opt. Lett. 21, 776-778 (1996)