PHASE-MODULATION EFFECTS IN SELF-DIFFRACTION

Phase-modulation effects in self-diffraction with two pump beams incid ent on a nonlinear medium were studied theoretically and experimentall y. Based on a two-level model and considering the influence of the pha se modulation on the phase matching, expressions describing the first- order and second-order scattered intensities were derived. The influen ces of phase modulation on the pump-intensity dependence and the sampl e-concentration dependence of the scattered intensities were discussed via numerical calculations. Experiments were performed with tetrahydr ofuran solution of 1,4-diethinyl benzene to demonstrate the theoretica l results. Some interesting results predicted by the theory, such as t he fact that the scattered intensities of the sample with lower concen tration can be larger than that with higher concentration at suitable high intensity of the pump, have been observed.