As it is well known from non-linear optics, the dielectric susceptibility χ of semiconductors is a function of the intensity of the impinging light. The non-linear part of the susceptibility gives rise to different light-mixing processes, the efficiency of which depends on the phase mismatch of the beams involved.
Part 1 Non-linear polarizability of semi-conductors: the nature of non-linear polarizability contribution of different elementary excitation to non-linearity of semi-conductors non-linear refraction of semi-conductors reactive mechanisms of refractive index non-linearity active mechanisms of refractive index non-linearity. Part 2 One-beam self-action of light in wide-gap semi-conductors: experimental methods of measuring the coefficients of refraction non-linearity and dynamics of self-action in semi-conductors experimental methods of measuring the coefficents of refraction non-linearity and dynamics of self-action in semi-conductors peculiarities of self-action of laser beams in wide-gap semiconductors the study of refractive index non-linearity in semi-conductors A2B6 anisotropy of refractive index nonlinearity in semi-conductors A2B6 the study of refractive index non-linearity in semi-conductors A2B6 - A3B5 the study of refractive index non-linearity in semi-conductors A4B4. Part 3 Two-beam light interaction in wide-gap semi-conductors: scalar self-diffraction of light waves in semi-conductors vector self-diffraction of light waves in semi-conductors experimental studies of dynamic holograms in wide-gap semi-conductors. Part 4 Four-wave light mixing in wide-gap semi-conductors: theory of degenerate six-photon mixing in semi-conductors experimental set up efficient phase conjugation under degenerate four-wave mixing and phase synchronism violation PC experiments under degenerate four-wave mixing in other wide-gap simi-conductors. Part 5 Optical bistability in wide-gap semi-conductors: classification of optical bistable schemes resonatorless optical bistable schemes.
The theory of polarised light phase conjugation (PC) in non-degenerate four-wave mixing in a resonant medium has been developed in the irreducible tensorial formalism. The theory is applied to a wave with any polarisation in a resonant medium with levels of arbitrary momentum in the absence of pump-induced saturation effects. The formula for the non-linear susceptibility of the medium has been found and it is shown that the change of the polarisation at PC is essentially connected with the relaxation of the atomic multipole momenta (population, orientation and alignment). Wave equations were investigated for different pump-wave polarisations and three different physical mechanisms of the PC are discussed. The influence of the different relaxation rates of the atomic multipole momenta on the PC reflectivity has been investigated. The spectral dependence of the reflectivity and the spectral ranges which depend on the wave polarisation are found. For motionless atoms with small momenta (J 1 = 1 / 2 to J 2 = 1 / 2 , J 1 =1 to J 2 =0), exact formulae for the non-linear susceptibility of the medium as a function of pump intensity were found. The spontaneous decay of higher level to the lower one was taken into account. Because of optical pumping, saturation effects can be shown at considerably smaller intensities than in the usual two-level system. The exact expressions for the PC reflectivity at different polarisations of the pump waves are given.
A set of nonlinear spectroscopic measurements with quantum light is presented. It involves a strong pump with frequency ωpu and a weak probe at ωpr interacting with a solid state target to generate a conjugated beam ωc=2ωpu−ωpr via nondegenerate four-wave mixing. The χ(3) susceptibility can be measured by the noise spectra of the intensity difference of the squeezed beams. We discuss three spectroscopic setups based on squeezed light: first, single four-wave mixing in a single crystal; second, cascading scheme involving two crystals; third, an SU(1, 1) interferometer based on two separate four-wave mixing processes. We further investigate the microscopic noise and optical losses in all three setups. Simulations are presented for silicon-vacancy color centers in diamond.