Theory and design of integrated optical isolators and broadband couplers using Fresnel zone plates

Abstract

This thesis is divided into two main sections: the first containing the analysis of the broadband vertical coupler, and the second involving the theory and design of the integrated optical isolators. In the first part we propose, theoretically investigate, and numerically demonstrate a compact (less than 10[mu]m) broadband (more than 300nm) fiber-chip vertical coupler. The structure utilizes a Fresnel lens, or more advanced integrated optics, placed above a short, ridge and deep etched, vertical coupler in a Si waveguide. This optics is placed in order to match the radiating fields to the fiber mode. We use semivectorial simulations with a simple stochastic optimization to design a good integrated optics without cylindrical constrains. Three-dimensional Finite-Difference Time-Domain (FDTD) simulations reveal ~ 50% fiber coupling efficiency and a bandwidth of 200nm. In the second part we propose, theoretically investigate, and numerically demonstrate six designs of integrated optical isolators. We first derive analytically the value of the off-diagonal gyrotropic permittivity tensor element, Eg. We then use this value to calculate a non-reciprocal phase shift in a Manganese, and a N/P doped silicon waveguide using analytic, perturbation, and a novel mode numeric approach. Finally, using the obtained magnitudes of the nonreciprocal phase shifts six integrated optical isolator designs are proposed.