Four-wave mixing oscillation in a cavity using sodium vapor

The experimental characteristics of a four-wave mixing oscillator which uses sodium vapor enclosed in a linear cavity are described. The pump beam depletion and the enhancement of the fluorescence induced by the four-wave mixing oscillation are studied. The situations of pump beams of the same frequency and of different frequencies are considered. In both cases, the output beam almost always exhibits a bistable behavior. The bistability is observed by varying the length of the cavity, the pump beams being constant, or by varying the pump beam intensity, the length of the cavity, the remaining constant. With degenerate pump beams, the phase and the frequency of the output beam is compared to those of the pump beam. In a study of the noise of such a degenerate four-wave oscillator both in the case of degenerate and nondegenerate pumps, a very important phase sensitive noise was observed. This feature was observed for nondegenerate oscillation.<>