Investigation of the modes of multilayer optical waveguide structures

Thesis (Ph. D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1989.This thesis is directed toward studying modal properties of multilayer optical waveguides. The purpose of the investigation is to identify promising waveguide structures while providing insight into the operation of existing multilayer waveguides. A first step in this endeavor was the development of a computer program, which through its highly interactive user interface, provides a much needed computational utility to investigate complicated multilayer optical waveguide structures. It is capable of analyzing a large variety of planar structures for optical waveguide applications. A common trait of the waveguide modes studied in this thesis is that they are represented by propagation constants that are complex numbers, indicating associated attenuation of these modes. Two particular classes of waveguide structures are extensively investigated: metal-oxide-metal (MOM) tunnel junctions in which the attenuation is due to ohmic losses of the constituent metallic layers, and silicon waveguides fabricated through the use of the Separation by the IMplantation of OXygen (SIMOX) process where the complex propagation constant is due to substrate leakage. A thorough analysis of the modal properties of a large variety of MOM tunnel junctions is performed. The structures investigated include aluminum as the bottom electrode, and one of gold, silver, or copper as the top electrode. The results thus obtained help to clarify certain points of dispute that exist in the present understanding of the light emission process in such structures. MOM tunnel junction structures are fabricated, and the measured values of the waveguide mode effective indices are in good agreement with the results of the computer calculations. A new type of silicon-based optical waveguide structure (SIMOX) is proposed for operation in the near infrared. The compatibility of its fabrication process with the microelectronics silicon-on-insulator device fabrication techniques makes it a potential candidate for optical and electronics integration. The analysis of SIMOX waveguide structures indicates modal properties that are sufficient to pursue this emerging technology for optical waveguide applications. The initial experiments conducted on SIMOX waveguide samples confirm the predicted properties of these new type of waveguides, and these grating coupling experiments are the first ones showing optical guided waves are indeed supported by SIMOX structures