Abstract

We have investigated how the interaction of a probe wave with one or two degenerate pump waves in an atomic potassium vapor affects the noise properties of the transmitted cw probe wave. In the case of a single pump wave, the two-beam-coupling gain^[1] experienced by vacuum sidebands of the probe wave leads to the amplification of intensity fluctuations of an initially shot-noise-limited probe field.^[2] In the case of two degenerate pump beams, a degenerate probe beam can be amplified by a factor of~15 by means of a forward four-wave mixing process. At a lower gain of~6, the correlated intensity fluctuations between the probe beam and the generated idler beam make it possible, in principle, to amplify the probe beam while introducing less noise than the standard quantum-mechanical amplifier noise limit^[3] requires.

© 1992 IQEC