Novel Materials and Processes for Fabrication of Integrated Photonic and Opto-Electronic Devices

Abstract

Photonic devices, traditionally made in silicon, silicon dioxide and III-Vsemiconductor based materials, are the basis for many advances in the optical telecommunication area. Thin films are the foundation for these devices. Typically thin films are made from methods that involve expensive or complicated processes, such as chemical vapor deposition (CVD), sputtering, and electron beam evaporation. In this work, design, fabrication, and characterization is done with novel sol-gel and polymer materials utilizing new processes for the creation of optical waveguides, interconnects, and electro-optic modulators. Sol-gel, which begins as a suspension of particles in a liquid called a sol, is synthesized and used to create thin films of TiO2, SiO2, and blends of the two. Films created from the sols range from 100nm to 5 microns when formed by the spin coating method. TiO2 films have a high index and high dielectric constant that make them ideal for small single mode waveguides, thus allowing devices to have a smaller and condensed footprint. The sols can be combined to create a TiO2-SiO2 blend with highly tunable refractive index and dielectric properties. New sulfur-based polymers are also used to create thin films of hybrid chalcogenide glass using both melt pressing and the spin coating methods with the polymer dissolved in a solvent, creating films that range from 1-100 microns. These sulfur polymer based films have tunable high refractive indices, as well as good transmission at telecom wavelengths, which makes them excellent candidates for compact integrated photonics. 16 All films were characterized to determine physical properties such as crystal structure, optical properties such as refractive index and transmission, and dielectric properties. Films created from both the sol-gel method and the sulfur polymer can be patterned to create optical waveguides and electro-optic devices. The films from the sol-gel method can be processed using typical silicon fabrication techniques such as UV and electron beam lithography, and reactive ion etching (RIE). For sulfur polymer films, processes were developed for patterning including direct writing in the material, as well as reductive processes such as RIE. The tunability of the properties of the sol-gel and sulfur polymer materials allows them to be customized for a variety of applications. This, along with the high refractive indices and ease of processing, allows for design of optical and photonic devices that are on par or better than conventional devices, while using processes that are simple, cost effective, and rapid.