Cross-phase-modulation-induced self-focusing in parametric oscillators

The dependence of spatial self-focusing on resonator detuning is experiment ally investigated in the active medium of a photorefractive oscillator whic h is a parametric oscillator with narrow gain linewidth. Beam diameter of t he TEM00-mode and beat frequency of the TEM00-mode and another simultaneous ly emitted transverse mode depend on detuning like a dispersion-shaped func tion. The maximum strength of self-focusing and the corresponding frequency shift are in the resonator strongly reduced with respect to single-pass wa ve mixing.