Felinskyi G. Nonlinear photon-phonon interaction and coherent processes in optical waveguides

The dissertation is devoted to comprehensive research of physical processes due to nonlinear photon - phonon interaction at light scattering and diffractions on the optical and acoustic phonons respectively. The influence of phonon vibrations on the dielectric and nonlinear properties formation of the material of optical waveguides, the coherent processes results in optical waveguides including both the planar waveguide mode diffraction on the acoustic waves and the Raman lasing and light amplification in the optical fibers above the stochastic Stokes hum noise are investigated. The research results on phonon systems dynamics at nonlinear interaction of laser radiation with molecular vibrations in optical waveguides are presented in dissertational work. Experimental techniques and research results of the photon - phonon interaction, applied in laser diagnostics of the technological process parameters for creation of optoelectronics and integrated acousto-optic devices are stated. Physical features of coherent interaction of laser radiation with nonlinear perturbation of dielectrics and optical waveguides, methodology of their numerical modeling, and also experimental test results of devices for processing radio signals are considered. The common physical mechanisms connected with influence of optical polar vibrations on formation of linear dielectric properties and quadratic nonlinearity in crystals without the inversion center is found out using the Raman spectroscopy methods. The main physical differences accompanying occurrence of cubic nonlinearity in amorphous material of a silica glass of optical fibers, in comparison with modeling nonlinear crystals are analyzed. The original technique of spectroscopic modeling of nonlinear photon - phonon interaction processes, and also its application results are submitted at the analysis of Raman amplification of optical radiation in single mode fibers with terahertz frequencies working band. The physical reasons of huge excess of amplification of a powerful coherent signal above amplification of weak non coherent optical noise in nominal pumping power mode are established on the basis of direct measurements of amplified spontaneous emission in the real fiber Raman amplifier. Consequences of a modes concurrence appeared in nonlinear stimulated Raman process which entail increase in the signal to noise ratio at output of the distributed optical amplifier in comparison with a case of amplifier absence are analyzed and therefore there is a radical reduction of noise figure of such amplifier.