Investigations on the Biexcitons by Optical Resonant Degenerate Mixing
A previously described method of active nonlinear spectroscopy, applied to CuCl, has very clearly displayed a quite general peculiarity of the biexciton states in semiconductors: their autoionizing character. This method has been used to investigate the Γ1 biexciton in CdS, where the theoretical and experimental conditions are by far more complicate. In that uniaxial compound it is possible, through a proper choice of the polarization of the impinging beams to discriminate among the various intermediate levels involved in that third order process. Then, the leading phenomenon which gives rise to the observed signal can be selected to be 3 or 2 times resonant, with a correspondingly “large” or “low” absorption coefficient. A theoretical analysis is presented, which accounts for the competition between on the one hand the non-linear gain and optical Kerr effect and on the other hand the one and two-photon absorptions.
KeywordsOscillator Strength Physical Review Letter Optical Kerr Effect Photon Resonance Exciting Beam
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