TRANSIENT ANALYSIS OF 4-GRATING COPOLARIZED 4-WAVE-MIXING IN SATURABLE GAIN MEDIA WITH FINITE PROBE

We model transient copolarized degenerate four-wave mixing in a satura ble gain medium, using pulses of duration much shorter than the popula tion lifetime with a finite probe beam. initially we describe a model to include the simultaneous existence of both the reflection and trans mission gratings for arbitrary field strengths. Then we develop a mode l to include all four possible gratings, including standing-wave grati ngs between counterpropagating pump beams and the probe and conjugate beams. By use of two expansion methods for the higher-order grating te rms it is possible to model regimes in which either one grating is arb itrarily strong or all four gratings are strong. Comparisons are made among models including one, two, and four gratings. Good agreement is found between the theoretical four-grating case and pulsed copolarized degenerate four-wave mixing experiments in laser-pumped Ti:sapphire f or a finite probe beam. (C) 1996 Optical Society of America.