Diffraction properties of vector synthetic volume index gratings

We investigate the diffraction properties of vector synthetic gratings, whi ch consist of two volume index gratings with different grating wave vectors , using coupled-wave analysis. These index gratings can be obtained in phot orefractive materials or in Bragg cells with two driving acoustic waves. We consider the case of pseudo phase matching in which a Bragg mismatch exist s in the scattering from the individual index gratings while a Bragg condit ion is satisfied for the scattering from the vector sum of the two index gr atings. Analytic expressions for the diffraction efficiency as well as the amplitude of the three waves involved are obtained. The results are present ed and discussed. (C) 2000 Optical Society of America [S0740-3224(00)02106- 8].