Experimental and numerical study of properties of nematic liquid crystal waveguide structures

Nematic liquid crystal optical waveguide structures were studied by the numeric simulation and experimentally. Two types of optical smoothly-irregular waveguide structures promising for application in telecommunications and control systems are studied by numerical simulation and experimentally: liquid thin waveguide lens and thin film generalised waveguide Luneburg lens. The dependence of attenuation coefficient (optical losses) of the waveguide modes and the effective sizes (correlation radii) of the quasi-stationary irregularities of the liquid-crystal layer on the linear polarization of the incident laser radiation and the presence of pulse-periodic electric field were experimentally observed. An estimate is made of the correlation radii of liquid-crystal waveguide quasi-stationary irregularities. The observed decrease in the attenuation coefficient of the waveguide modes and the effective sizes of irregularities in the liquid-crystal layer, when the external electric field is switched on, explained by the effect of the decrease in the fluctuations correlation radii of the local orientation of the molecules of the liquid crystal. The obtained results are undoubtedly important for further research of dynamic processes inside non stationary waveguide liquid crystal layers, both from the theoretical point of view for understanding kinetic processes in the liquid crystals, and with practical, - in the organization and carrying out suitable experimental researches. © 2018 IEEE

Microcrystal ordering and second-order optical susceptibilities of zinc oxide films

Second harmonic generation in zinc oxide films deposited by the hydrothermal method was investigated. A correlation between second-order optical susceptibility tensor components d311 and d333 was studied by using the model of noninteracting microcrystals, and the origin of different contributions to the film nonlinearities was discussed. The change of stacking sequences and the inhomogeneity in the distribution of the nonlinearities over the film thickness are the most probable effects hindering the investigations of the thickness dependence of ZnO film nonlinearities. A model of the inhomogeneous distribution of the nonlinearities over the film thickness was used for doing an analysis of the experimental data features, which were accounted for by a sublayer, adjacent to the seed layer, and possess high optical nonlinearity, d333 = -72.6 pm/V. © 2022 Author(s)

Modeling Static Electric Field Effect on Nematic Liquid Crystal Director Orientation in Side-Electrode Cell

A two-dimensional model of Fredericks effect was used for the investigation of the static electric field influence on nematic liquid crystal director orientation in the side-electrode cell. The solutions of the equations describing the model were obtained by finite-difference methods. Fredericks transition threshold for the central part of the cell, as well as dependencies of the distribution of the director orientation patterns on the electric field and location, were obtained. The numerical results are found to agree qualitatively with the experiment. Further investigations are needed to elucidate completely the Fredericks effect. © 2018 The Authors, published by EDP Sciences

Modeling Static Electric Field Effect on Nematic Liquid Crystal Director Orientation in Side-Electrode Cell

A two-dimensional model of Fredericks effect was used for the investigation of the static electric field influence on nematic liquid crystal director orientation in the side-electrode cell. The solutions of the equations describing the model were obtained by finite-difference methods. Fredericks transition threshold for the central part of the cell, as well as dependencies of the distribution of the director orientation patterns on the electric field and location, were obtained. The numerical results are found to agree qualitatively with the experiment. Further investigations are needed to elucidate completely the Fredericks effect. © 2018 The Authors, published by EDP Sciences