Events Calendar

EE-EP Seminar - Kejie Fang, Friday, February 19th at 2:00pm in EEB 132

Speaker: Kejie Fang, California Institute of Technology

Talk Title: Integrated Hybrid Photonics-”Emergent Control and Application for Light and Sound at Nanoscale

Abstract: The bottleneck of bandwidth limitation and power dissipation in today's electronic microchips is conflicting with the exceeding demand for information communication and processing. Light, due to its intrinsic high frequency and environment-insensitivity (owing to its charge neutrality), is expected to bring solutions to this fundamental challenge. By the same token, certain functionalities in optical information processing will require a hybrid architecture interfacing different materials and light-matter interactions. With technical advances in nanofabrication, it is now possible to manipulate light and enhance light-matter interactions in on-chip, nanoscale photonic structures.
In this talk, I will present my research in two integrated hybrid photonic architectures. First is optoelectronic integration, where we achieved novel active control of light through an electric drive which dynamically modulates the refractive index of silicon photonic structures, leading to an effective magnetic field for photons and topological light propagation. These novel interactions are unreachable in static or passive dielectrics and provide a solution for on-chip optical isolation that is essential for stable and energy efficient optical communication. In the second part of my talk, I will present work on another hybrid architecture that interfaces light and sound: optomechanical crystals. This architecture allows for simultaneously engineering of optical and mechanical properties as well as photon-phonon interactions. Combining electron beam lithography and scanning probe microscope tuning, we fabricated cavity-optomechanical circuits on silicon microchips to realize radiation-pressure controlled microwave phonon routing. We applied these devices for microwave-over-optical signal processing with low energy and high efficiency. The nanoscale mechanical vibration is also used to achieve optical non-reciprocity in the optomechanical circuit. These achievements hold promise for hybrid photonic technology for light-based communication and processing in an integrated, chip-scale platform.


Biography: Kejie Fang is a Postdoctoral Scholar in Applied Physics at California Institute of Technology, working with Prof. Oskar Painter. He received his B.S. in physics from Peking University, and his M.S. in electrical engineering, Ph.D. in physics, both from Stanford University under the supervision of Prof. Shanhui Fan. Kejie's research interests include optomechanics, nanophotonics, and spin photonics, with a theme to develop novel chip scale devices and systems for light-based applications including optical information communication and processing. During his Ph.D., he proposed and demonstrated for the first time an effective magnetic field for photons which provides a solution for on-chip optical isolation. At Caltech, he developed integrated cavity-optomechanical circuits for on-chip information processing using nanoscale optical and acoustic excitations. Kejie has published 15 peer-reviewed papers in leading journals including Nature Photonics, Physical Review Letters, and Nature Communications. Kejie was a William R. and Sara Hart Kimball Fellow at Stanford University and also a recipient of OSA Outstanding Reviewer Award in 2014.

Host: EE-Electrophysics

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 132

Audiences: Everyone Is Invited

Contact: Marilyn Poplawski