Spatial solitons and optical vortices in nematic liquid crystal

Abstract

Liquid crystals have been all along a fertile background for scientific re- search, from mathematics to materials science to optics; their use is not limited to displays but extends to nonlinear optics, switching, routing. Due to their extreme sensitivity to electric fields at frequencies ranging from con- tinuous wave to optics, they are also nonlinear media supporting the gener- ation and propagation of self confined beams, called spatial optical solitons, at very low powers. Spatial optical solitons have the property to propagate without diffraction, as diffraction is compensated by nonlinear self-focusing of the medium in which light is injected, resulting in self-induced waveg- uides. These waveguides in nematic liquid crystals can in turn confine and route other optical signals and can be reconfigured, optically or electri- cally, as soliton trajectories can be controlled by other fields, paving the way to optical and all-optical manipulation. Nematic liquid crystals have also been recently employed with success in the so called singular optics, in which the key parameter is the topologic singularity carried by the phase of an electromagnetic wave. In this thesis I will report on my work on spatial optical solitons and optical singularities in nematic liquid crystals. In the first chapter I will outline the basic properties of nematic liquid crystals, with an introduction to solitons in nonlinear optics. In the second I will discuss the generation of optical spatial solitons and their steering in ne- matic liquid crystals. In the third chapter I will present the basic concepts of singular optics , followed by a discussion on vortices and their generation using optical induction of defects.