Abstract

Scattered light from a single laser beam incident on a photorefractive crystal is amplified in certain directions by two-wave mixing, producing beam fanning. A subset of the multitude of photorefractive-index gratings responsible for beam fanning is phase matched for conical diffraction. These cones of light appear with the same polarization as the incident beam and fanned light in Sr_xBa_1−xNb₂O₆ and with the opposite polarization in BaTiO₃. Measurement of the cone angle can provide accurate values of the birefringence of the crystal as a function of wavelength. Also, the intensity distribution of the stimulated light scattering reveals the optimal orientation and spacing of the photorefractive gratings for beam coupling, as will be shown for a cerium-doped sample of Sr_xBa_1−xNb₂O₆ with x = 0.75. Additionally, intense stimulated scattering, reflected back toward the incident beam by the crystal surfaces, can serve as the pumping beams for four-wave mixing to generate a self-pumped phase-conjugate replica of the incident beam in both BaTiO₃ and Sr_xBa_1−xNb₂O₆.

© 1986 Optical Society of America