Novel Optical Materials for Passive Photonic Applications

Abstract

Advances in photonic materials are critical to the progress of photonic devices and optical systems. Even though a variety of materials, e.g. semiconductors, oxide based glasses, and polymers exist which are being used for numerous applications, there is a growing need to develop and find new materials in order to push the limits we are bound by with conventional materials, in pursuit of higher performance, higher levels of integration and lower cost. In this realm, new material development has had a considerable impact, as it is the material properties (optical, thermal, mechanical, electrical, ...) in addition to their processing and compatibilities with standard processes that enable us the creation of entirely new devices or improve the performance of currently available optical devices. In this dissertation, I will demonstrate the application of two new materials for novel photonic components. In the first part of the dissertation, I discuss how a hybrid approach to the silicon photonics platform can reduce thermal sensitivity using sol-gel based inorganic-organic hybrid materials. The approach is to design the optical waveguide so that it maintains its performance in a passive manner in response to environmental temperature variations and, thus, does not need external temperature control resulting in reduced electrical power consumption. Sol-gel materials are well-known, but they haven’t been exploited like polymers and titanium dioxide to be cladding layers to enable athermal silicon waveguides. In this work I show their advantages with respect to previous materials that were employed for athermal microring resonators. I studied the thermal curing parameters of the sol-gel and its effect on thermal wavelength shift of the microring resonance. With this method, I was able to achieve a thermal shift down to -6.8 pm/°C for transverse electric (TE) polarization, as well as thermal shifts below 1 pm/°C for transverse magnetic (TM) polarization in the C band under different curing conditions, all while preserving high Q resonator performance. The results and methodology described opens a new and more manufacturable approach to attain athermal silicon photonic devices. In the second part of the dissertation, I introduced a new, sulfur rich, low cost copolymer material developed by our colleagues in the chemistry department. This copolymer has unique properties that conventional optical polymers, such as polymethylmethacrylate and polycarbonate, lack, while also having low cost. I demonstrated that these polymers have very good processing capabilities, being easily moldable to make free space optical elements and solution processable for use in integrated optics. I studied their linear and nonlinear optical properties, finding them to possess high refractive indices and transparencies over a wide range from 550 nm to 6 µm, except for a small region of absorption from 3-3.3 µm. Finally, I demonstrated that these new copolymers are suitable and economical alternative for shortwave and midwave infrared optics (SWIR and MWIR, respectively).