In contrast to the traditional spectroscopic techniques, the picosecond stimulated Raman scattering (SRS) in fibers permits one to determine the anharmonicity constants for silica tetrahedron vibrations and local dopant vibrations. The results of new experiments using the technique of picosecond SRS excitation in pure and doped silica fibers are presented. Apart the fundamental Raman-active silica and dopant vibrations and their overtones the intense combination bands were detected. The comparative studies of undoped and erbium-doped silica fibers were made. When the photoinduced changes took place in a silica fiber core the distinct combination SRS bands were observed, whereas the presence of an erbium ions in silica network didn't disturb the SRS bands originated from silica tetrahedron vibrations.
The nonlinear Bloch's theorem for the fundamental and high-order Schrödinger solitons in periodic dispersive and nonlinear structures has been proven. It is shown that bright and dark solitary nonlinear Bloch's waves exist only under certain conditions and that the parameter functions describing dispersion and nonlinearity periodic inhomogeneities cannot be chosen independently. The formation, interaction and stability of the fundamental and high-order solitary nonlinear Bloch waves have been investigated.
The methodology based on the quasi-soliton concept provides for a systematic way to discover an infinite number of the novel stable bright and dark soliton management regimes for the nonlinear cubic-quintic Schrödinger equation model with varying dispersion, nonlinearity and gain or absorption. Q uasi-soliton solutions for this model must be of rather general character than canonical solitons of standard nonlinear Schrödinger equation model, because the generalized model takes into account the saturation nonlinear effect and arbitrary variations of group velocity dispersion, nonlinearity and gain or absorption. Novel topological and nontopological quasi-soliton solutions for the nonlinear cubicquintic Schrödinger equation model have been discovered. It is shown that, today, the most attractive media to discover novel topological quasi-solitons are organic thin films and polymeric waveguides.