Degenerate multiwave mixing and phase conjugation in silicon

We present a detailed theory and experiment on degenerate-multiwave-mixing- mediated beam amplification in the semiconductor silicon. The theory accounts for several important factors, such as coupling to higher-order diffractions, intensity-dependent self- and mutual-phase modulations, losses, phase matchings, intensity ratio among the input beams, etc. In the silicon case under study, involving the generation of electron-hole pairs by 1.06m laser pulses, the intensity-dependent absorption loss and the temporal and/or spatial intensity profile of the input laser beam are also explicitly accounted. The experimental results for probe-gain dependences on several parameters are in good agreement with the theory. The important role played by the side diffractions in mediating the amplification of the probe is also apparent in our experiment on phase conjugation of the probe beam, where a strong dependence of the phase-conjugation reflection on the pump- to probe-beam ratio is observed, similar to the probe-gain dependence.