Effect of the group velocity mismatch and dispersion of nonlinear susceptibility on the modulation instability of electromagnetic waves in a medium with quadratic nonlinearity

Modulation instability of continuous plane waves of the pump beams and the second harmonic that are described by the set of equations for the process of second-harmonic generation with allowance made for the dispersion of nonlinear susceptibility is considered. The case of type I phase matching is analyzed. In the regions of anomalous and normal group velocity dispersion, the instability increments are determined as functions of the frequency and the wave numbers of perturbations. It was found that the difference in the group velocities of the interacting waves exerts the most substantial effect on the evolution of the modulation instability. (C) 2002 MAIK "Nauka/Interperiodica".