Effects of Gaussian-beam averaging on phase conjugation and beat-frequency spectroscopy

Abstract
The effects of Gaussian-beam averaging with various apertures are derived for three-wave mixing in nonlinear two-level media. The model studies the phase transition from plane-wave to pure Gaussian saturation. Applications to phase conjugation, beat-frequency spectroscopy, and laser-optical-bistability instability phenomena are considered. The Gaussian beams are seen to reduce or wash out dynamic Stark splittings observed for plane-wave saturation. For strong saturation, the side-mode gain/absorption coefficient versus detuning yields slightly larger gain for the homogeneously broadened laser instability but substantially curtailed gain for the corresponding absorptive optical-bistability instability.