Optical parametric oscillation in an LiNbO3 crystal in the presence of a photorefractive diffraction grating

An investigation was made of optical parametric oscillation in an LiNbO₃ crystal in the presence of a photorefractive interference diffraction grating induced in the bulk of a crystal by two pump beams. When the Bragg diffraction and noncollinear phase matching conditions were satisfied simultaneously by components of the radiation generated parametrically, selection was exhibited by the emission spectrum: the width of the spectrum in the plane of convergence of the pump beams was 3.5 cm^–1 when the divergence of the radiation was 1 mrad.