Nematicons: Spatial Optical Solitons in Nematic Liquid Crystals

Chapter 11: Power-Dependent Nematicon Self-Routing

Alessandro Alberucci, Armando Piccardi, AND Gaetano Assanto

Nonlinear Optics and OptoElectronics Lab, University ROMA TRE, Rome, Italy

11.1 Introduction

Most studies on reorientational nematicons were carried out in the limit of small nonlinear effects, an assumption often adopted in nonlinear optics [1]. Perturbational models in nonlinear optics are based on a nonlinear polarization much smaller than the linear counterpart , allowing the use of well-known techniques, for example, coupled-mode theory [2]. In the reorientational nonlinearity of nematic liquid crystals (NLC), perturbative approximations require light-induced variations in the director field to be negligible when compared with the molecular distribution in the absence of illumination. The first theoretical models on nematicons made extensive use of this hypothesis [3–5], making a drastic simplification of the problem. On the other hand, such models are inherently unable to describe a few phenomena expected on physical grounds, such as saturation of the nonlinearity and dependence of nematicon trajectory on power, the latter independent of excitation according to first-order perturbation theory. In particular, nematicon paths change with input power when the optical reorientation ...