Degenerate Four-Wave Mixing In Nonlinear Media With Local Response: Free Carrier And Space Charge Gratings, Strong Coupling

AbstractBackward wave degenerate four -wave mixing in solid nonlinear materials CdTe andLiTaO is investigated. Amplified reflection of the fourth wave with wavefront complex conjugate to the signal wave is first observed in solid state medium. The theory of four -wave mixing for the case of strong coupling of the signal and pump beams is develo- ped. It is shown that total intensity of each pump wave may be transfered into one ofthe signal waves for equal intensities of the pump beams.Introduction Backward wave degenerate four -wave mixing ( F W M ) and phase conjugation (PC) in op-tics are at present topics of particular interest both in the theory and in experi-ment / for reference see review articlel /. The generation of PC waves due to F W M isobserved in various nonlinear media: absorbing liquids 3, metal vapors4, semiconductors5, ionic , electrooptic7and ferroelectric8 crystals. In all solid -state materials the effi- ciency of F W M, i.e. the ratio of the intensity of PC wave to that of the signal wave,was very small, about few per cent. We report in this paper the first observation ofamplified reflection of PC wave in solid materials / two time net amplification for CdTe