Boundary conditions for optical rectification and application to degenerate four-wave mixing in a novel geometry

We derive general boundary conditions for optical rectification of Gaussian beams and discuss the effect on cascaded optical rectification and the lin ear electro-optic effect as well as terahertz generation. These conditions are applied to degenerate four-wave mixing in a novel geometry in which we experimentally demonstrate, for the first time to our knowledge, that the c ombination of optical rectification of a single pump beam and the linear el ectro-optic effect produces a refractive-index grating in the transparent s pectral region of the inorganic crystal KNbO3. The intensity of a probe bea m diffracted by this grating was determined and corresponds to the theoreti cally expected result obtained from the known material parameters. (C) 2001 Optical Society of America.