PHASE-CONJUGATION PROPERTIES OF 2-PHOTON-PUMPED BACKWARD-STIMULATED EMISSION - II - THEORETICAL-STUDIES

Recent experimental results have shown that the highly directional fre quency-upconverted backward-stimulated emission from a two-photon-pump ed lasing medium possesses the property of optical phase conjugation. To explain this property, a Gabor's quasi-collinear holographic model is proposed for a two-photon-pumped gain medium. According to this mod el, the input IR pump beam (after passing through a phase-distorting m edium or an aberration plate) can be assumed to consist of two parts: an undisturbed regular portion and a phase-distorted irregular portion . These two portions interfere with each other and create a volume hol ographic grating within the pumped region inside the gain medium. Whil e an initial regular backward-stimulated emission (as a reading beam) is passing through this holographic grating, a diffracted wave is crea ted and amplified together with the reading beam. A rigorous mathemati cal analysis shows that under certain conditions, the combination of t hese two parts (the reading beam plus the diffracted wave) of the back ward-stimulated emission can be an approximate phase-conjugate field o f the total input-pump field. (C) 1998 Optical Society of America.