OP: Hybrid Silicon-Vanadium Dioxide Resonators for Tbps Optical Communication

Vanderbilt University, Nashville TN

Investigators

Abstract

Abstract Title Hybrid Silicon-Vanadium Dioxide Modulators for Record High Speed Optical Communication Abstract Nontechnical: It is increasingly difficult to raise computational processing speed simply by adding more transistors because feature sizes are approaching atomic dimensions, power and heat dissipation are problematic in small volumes, and bottlenecks in on-chip communication slow down data transfer. Among the most promising routes to significantly faster processing speeds is using light pulses to carry digital data. High-speed, low-power optical modulators that can encode signals in light are essential if computers are to achieve THz-scale processing using light on silicon chips. However, due to their intrinsic physical properties, all-silicon optical modulators cannot achieve signal modulation at such a high speed. In this project, hybrid silicon-vanadium dioxide optical modulators on a silicon chip are investigated for THz-speed modulation of light. Fundamental insights on the ultrafast behavior and intrinsic materials properties of the switching mechanism - the insulator-to-metal transition in vanadium dioxide - will also be developed in the project. Participating students will do cutting-edge research at the intersection of nanotechnology, physics, engineering, and materials science. Faculty and graduate students will share their enthusiasm for science, technology, engineering, and mathematics with middle and high school students in Metro Nashville and surrounding rural Tennessee counties by participating in successful outreach programs already established at Vanderbilt. Technical: High-speed, low-power optical modulators are essential to the future of silicon photonics as the solution to ultrafast communication. The goal of this project is to reach switching speeds of at least 500 GHz with an expenditure of 100 fJ/switch in hybrid silicon:vanadium dioxide photonics devices by exploiting the ultrafast insulator-to-metal transition of vanadium dioxide. The hybrid devices will also be used to probe the strong electron correlations that underlie the optically induced insulator-to-metal dynamics in vanadium dioxide. The specific objectives of the research are to: (1) fabricate hybrid silicon:vanadium dioxide photonic components and compare the switching speed of the optically and electro-optically induced phase transition in vanadium dioxide; (2) benchmark device performance against state-of-the-art simulations to learn how the phase change in vanadium dioxide controls the mode structure of optical pulses in the devices; and (3) measure the time-dependent dielectric function of vanadium dioxide in the telecommunications band by interferometric monitoring of the phase and amplitudes of optical pulses in Mach-Zehnder geometries. The intellectual merit at the heart of the project lies in its ambition to understand and exploit the ultrafast dynamics of the phase transition of vanadium dioxide near 1500 nm. The technological challenge is to demonstrate 500 GHz switching speeds in hybrid silicon:vanadium dioxide structures with micron-scale footprints using ultrafast lasers in the telecom band to initiate the phase transition of vanadium dioxide. This will require careful optical engineering to ensure low injection loss between the laser pump and the hybrid phase-changing structure. Demonstrating that the optically induced, ultrafast phase transition in VO2 can be harnessed in a practical, silicon-device-compatible architecture and processing regime would be a transformational step toward on-chip THz-scale processing. The project is inherently interdisciplinary, training students in optical science and engineering, silicon photonics, materials science, and advanced computational techniques. Project participants will engage in well-established science and technology outreach programs targeting middle and high school students in both Nashville city public schools and rural counties in middle Tennessee.