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Integrated cavity-optomechanics: emergent control and application of light and sound at nanoscale

Event Date: April 28, 2016
Speaker: Dr. Kejie Fang
Speaker Affiliation: California Institute of Technology
Time: 10:30am
Location: EE 317
Contact Name: Professor Andy Weiner
Contact Phone: 765-49-45574
Contact Email:
Priority: No
School or Program: Electrical and Computer Engineering


Next generation technology for information processing and sensing with quantum-enabled characteristics relies on innovative micro and nanoscale engineering. As device size becomes aggressively miniaturized, effective control of physical elements in devices tends to be more challenging. Due to high precision and energy efficiency, control via light and light-matter interaction has become an enabling factor for realization of novel nano and quantum technologies. With technical advances in nanofabrication, it is now possible to manipulate light and matter excitations with enhanced light- matter interaction in on-chip, nanoscale structures.

In this talk, I will present my research work in cavity optomechanics, an emerging framework for cavity-enhanced control of acoustic excitations using optical field. I will first introduce a novel chip-scale architecture that interfaces light and sound: optomechanical crystals, which allow for simultaneously engineering of optical and mechanical properties as well as photon-phonon interactions in nanoscale bandgap structures. Motivated by the goal towards an integrated system, I will show cavity-optomechanical circuits fabricated on silicon microchips to realize radiation-pressure force controlled microwave phonon routing. These devices are then applied for microwave-over-optical signal processing with low operation energy and high efficiency, as well as mechanical transducers that can interact with distinctive physical elements for the realization of a hybrid quantum photonic system. Furthermore, I will show through precision control of nanoscale mechanical vibrations with phase correlated optical fields, optical non-reciprocity is realized in the optomechanical crystal circuits. This substantial result leads to a solution for the long-sought on-chip optical isolation that is indispensable for stable and energy efficient optical communication. Further scaling up the cavity-optomechanical circuits, I propose a scheme to realize effective magnetic field for photons and phonons, and exotic topological optical and acoustic states. Based on these achievements, I will end up with outlook into developing a hybrid photonic system involving optomechanical elements for communication, sensing, and quantum technology in an integrated, chip-scale platform.


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 through design, modeling, and fabrication, for applications in communication, sensing, and quantum technology. During his Ph.D., Kejie proposed and demonstrated for the first time an effective magnetic field for photons which enables unprecedented control of light on chips. At Caltech, he developed integrated cavity-optomechanical circuits for signal transduction and communication using nanoscale optical and acoustic excitations. Kejie has published in field leading journals including Nature Photonics, Physical Review Letters, and Nature Communications. He was a William R. and Sara Hart Kimball Fellow at Stanford University and also a recipient of OSA Outstanding Reviewer Award in 2014.