SPATIOTEMPORAL RESONANCE IN GENERATION OF SUBHARMONICS, SUM AND DIFFERENCE FREQUENCIES IN PHOTOREFRACTIVE CRYSTALS

Illumination of a photorefractive crystal by light containing two inte rference patterns (generally running) is considered. As well as linear terms in the response, the nonlinear ones are calculated, correspondi ng to sum and difference spatial frequencies. Efficient recording of t hose nonlinear gratings due to temporal phase-matching, i.e. phase-loc ked detection, is predicted under the application of spatially homogen eous field with DC and/or with sinusoidal time dependence. Thresholds for parametric instabilities of the types of subharmonic generation ar e calculated for different cases.