Nonlinear response function in case of polariton Fermi resonance

Abstract

A response function describing processes with three electromagnetic waves (polaritons) in crystals has been defined. This function has been calculated by a specific method for the case of polariton Fermi resonance, i.e. when one of the polaritons interacts with the two-phonon states of a non-degenerate polar vibration. Some features of the three-polariton interaction in the two-phonon band have been investigated, like modulation and broadening of the spectrum, anti-resonance and wave-vector mismatch. The information obtained from nonlinear optical spectra about polariton and two-phonon states has been analysed.