Polarization dependent four-wave-mixing and two-photon coherence in solids

Polarization dependent degenerate-four-wave-mixing experiments on semiconductors (ZnSe, CdS) and dielectrics (NaCl, PbF/sub 2/) reveal the essential mechanisms of the bound-electronic /spl chi//sup (3)/. We show, for the first time, that the observed anomalous dispersion of the polarization dependent phase-conjugate reflectivity can be explained using a simple 3-band model. The near vanishing reflectivity in the two-photon coherence geometry is shown to be a consequence of the interference between transitions originating from heavyand light-hole valence bands. We also present measurements on the polarization dichroism of the nonlinear refractive index (n/sub 2/), in good agreement with this simple theory.<
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