JQI Seminar February 24, 2020 - Gaurav Bahl

"Non-reciprocal and robust photonics with opto-mechanical systems"

Speaker: Gaurav Bahl, Illinois

Abstract: Time-reversal symmetry is a defining property for wave phenomena in linear stationary media. However, broken time-reversal symmetry is required for producing essential nonreciprocal devices like isolators, circulators, and gyrators. Magneto-optic methods can enable nonreciprocal behavior for electromagnetic waves, but this approach does not readily translate to the microscale or for atomic-PNT technologies, compelling us to search for nonmagnetic solutions. This talk will describe our work to exploit light-sound interactions for producing strongly nonreciprocal behavior in chip-scale systems. The optomechanical physics within these devices enable fundamental experiments having analogies to quantum condensed matter phenomena, including phonon laser action, cooling, and electromagnetically induced transparency [1,2]. We demonstrate how mechanics is uniquely positioned to solve long standing challenges for photonic integrated circuits that are required for cold-atom microsystems and related quantum technologies [3]. Moreover, the underlying nonreciprocal behavior enables robust photonic devices that are immune to backscattering induced by material defects and disorder [4,5]. Time permitting, I will introduce our work on how a synthetic Hall effect can be leveraged to produce strongly nonreciprocal metamaterials [6], and some of our research efforts on robust topological pumping [7] and high-order topological insulators [8].