Europhys. Lett, 44 (5), pp. 592-598 (1998)
M. Vaupel 1 and O. Mandel 2
1 Laboratoire Kastler Brossel, University P. et M. Curie - Case 74,
75252 Paris, France
2 Physikalisch-Technische Bundesanstalt - 38116 Braunschweig, Germany
(received 13 March 1998; accepted in final form 15 October 1998)
PACS. 42.65Jx - Beam trapping, self-focusing, and
PACS. 42.60Fc - Modulation, tuning, and mode locking.
PACS. 42.65Hw - Phase conjugation, optical mixing, and photorefractive effect.
The dependence of spatial self-focusing on resonator detuning is experimentally investigated in the active medium of a photorefractive oscillator which is a parametric oscillator with narrow gain linewidth. Beam diameter of the -mode and beat frequency of the -mode and another simultaneously emitted transverse mode depend on detuning like a dispersion-shaped function. The maximum strength of self-focusing and the corresponding frequency shift are in the resonator strongly reduced with respect to single-pass wave mixing.