Modelling of the intensity-dependent refraction of conductive oxide thin-films with near-zero-permittivity through a nonlinear transfer matrix approach

Abstract

This thesis is intended to contribute to the analytical understanding of intensity-dependent refraction in homogeneous thin layers of transparent conductive oxides in the frequency region where the real part of the relative permittivity vanishes. The motivation for this investigation is the extraordinarily large and ultra-fast optical nonlinearity displayed by transparent conductive oxides in the near-zero permittivity region which turn them into a promising base material of new photonic devices. In order to achieve this goal, a simplified numerical model has been developed for studying the behaviour of the intensity-dependent refractive index, under steady state conditions, in homogeneous, one-dimensional layered systems of TCOs. The numerical model is based on an adaptation of the Nonlinear Transfer Matrix Method that enables the method to obtain the refractive index values as a function of local intensity values inside the material. The most important capability of this model is the ability to accurately relate experimentally acquired measurements with the material's microscopic properties as long as local saturation effects remain negligible.