Hybrid Silicon Nanophotonic Devices: Enhancing Light Emission, Modulation, and Confinement

Citation

Briggs, Ryan Morrow (2011) Hybrid Silicon Nanophotonic Devices: Enhancing Light Emission, Modulation, and Confinement. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/G19Z-CY24. https://resolver.caltech.edu/CaltechTHESIS:05312011-175622776

Abstract

Silicon has become an increasingly important photonic material for communications, information processing, and sensing applications. Silicon is inexpensive compared to compound semiconductors, and it is well suited for confining and guiding light at standard telecommunication wavelengths due to its large refractive index and minimal intrinsic absorption. Furthermore, silicon-based optical devices can be fabricated alongside microelectronics while taking advantage of advanced silicon processing technologies. In order to realize complete chip-based photonic systems, certain critical components must continue to be developed and refined on the silicon platform, including compact light sources, modulators, routers, and sensing elements. However, bulk silicon is not necessarily an ideal material for many active devices because of its meager light emission characteristics, limited refractive index tunability, and fundamental limitations in confining light beyond the diffraction limit.

In this thesis, we present three examples of hybrid devices that use different materials to bring additional optical functionality to silicon photonics. First, we analyze high-index-contrast silicon slot waveguides and their integration with light-emitting erbium-doped glass materials. Theoretical and experimental results show significant enhancement of spontaneous emission rates in slot structures. We then demonstrate the integration of vanadium dioxide, a thermochromic phase-change material, with silicon waveguides to form micron-scale absorption modulators. It is shown experimentally that a 2-µm long waveguide-integrated device exhibits broadband modulation of more than 6.5 dB at wavelengths near 1550 nm. Finally, we demonstrate polymer-on-gold dielectric-loaded surface-plasmon waveguides and ring resonators coupled to silicon waveguides with 1.0±0.1 dB insertion loss. The plasmonic waveguides are shown to support a single surface mode at telecommunication wavelengths, with strong electromagnetic field confinement at the polymer-gold interface. These three device concepts show that diverse materials can be integrated with silicon waveguides to achieve enhanced light emission, broadband modulation, and strong confinement, all while retaining the advantages of the silicon photonics platform.

Thesis Files