Control of the mode composition of optical radiation in a microstructured fiber

The construction structure of microstructured fibers is considered. A research scheme of the mode composition and defects control in optical fibers is developed. A microstructured fiber for studying optical vortex fields has been developed and manufactured. The results of studies of the same fiber structure and the distribution of optical radiation depending on the parameters of the technological cycle of its production are presented.

SPATIO-TEMPORAL STRUCTURE OF CHERENKOV RADIATION EXCITED BY A LASER PULSE IN AN IONIC DIELECTRIC WAVEGUIDE

The process of excitation of Cherenkov electromagnetic radiation by a laser pulse in an ionic dielectric waveguide, is investigated. The frequency spectrum and mode composition of the Cherenkov radiation are determined. The spatio-temporal structure of the Cherenkov electromagnetic field is obtained and investigated.

Digital analysis of a speckle pattern of chaotic mode composition and restoration of a regular intensity pattern after a multimode fiber

A process of mode matching in a chaotic speckle pattern without a reference beam responsible for the formation of a holographic grating was studied experimentally and theoretically. Our approach was based on measuring the amplitudes and phases of the Hermite-Gauss (HG) and Laguerre-Gauss (LG) modes in a speckle pattern formed by the radiation of a multimode gradient fiber. The speckle pattern was formed in a hologram of a spatial light modulator using a multimode gradient fiber model while taking into account the mode and polarization dispersion, as well as random phase jumps of each eigenmode. We managed to match 210 modes of the speckle pattern and restore not only the original pattern, but also each structured LG mode and the entire chain of HG eigenmodes.

Bifurcating reactions: distribution of products from energy distribution in a shared reactive mode

Reactive Mode Composition Factor (RMCF) analysis is a powerful tool to forecast the product distribution of bifurcating reactions through analysis of the kinetic energy distribution within the first transition state traversed by the reacting system.

TERAHERTZ PHOTONICS AND SPECTROSCOPY ON NOVOSIBIRSK FREE ELECTRON LASER

A review of experiments in the field of photonics and plasmonics, recently performed with the Novosibirsk free electron laser (NovoFEL) is given. Parameters of NovoFEL radiation and user workstations are described. Considerable attention was paid to the development and testing of quasi-optical elements designed for this range and to methods for the formation of powerful beams of terahertz radiation with a given mode composition. The use of terahertz radiation in the spectroscopy of gases and semiconductors, in generation and study of surface plasmon polaritons, as well as the use of the latter for the study of surfaces and in communication applications is described.