DISTORTION-FREE GAIN AND NOISE CORRELATION IN SODIUM VAPOR WITH 4-WAVE-MIXING AND COHERENT POPULATION TRAPPING

We observed optical gain as great as 30 with nearly distortion-free be am propagation in optically dense sodium vapor, using four-wave mixing . Moreover, 15-dB classical noise correlations were seen in the amplif ied probe and conjugate beams. To achieve this performance in such a s trongly absorbing medium, one must suppress unwanted absorption and se lf-focusing effects. This is accomplished with coherent population tra pping. (C) 1997 Optical Society of America.