Colloquium - Dr. Gaurav Bahl | Department of Physics

Colloquium - Dr. Gaurav Bahl

Event Information
Event Date: 
Tuesday, October 31, 2017 - 3:15pm
Event Location: 
Physics Building - Room 104

Assistant Professor - Mechanical Science & Engineering

University of Illinois

Discussion: Chirality and non-reciprocity in optomechanical resonator systems


Time-reversal symmetry is a property shared by wave phenomena in linear stationary media. However, broken time-reversal symmetry is required for synthesizing nonreciprocal devices like isolators, circulators, gyrators, and for topological systems supporting chiral states. Magnetic fields can of course enable nonreciprocal behavior for electromagnetic waves, but this method does not conveniently translate to the chip-scale or to the acoustic domain, compelling us to search for nonmagnetic solutions.

We have adopted a unique approach to address this challenge through the use of co-localized interacting modes of light and sound in resonator systems. The acousto-optical physics within these systems enable fundamental experiments having analogies to condensed matter phenomena, including phonon laser action [1], cooling [2, 3], and electromagnetically induced transparency [4]. This talk will describe our experimental efforts to exploit the momentum conservation rules intrinsic to light-sound interactions for producing strong nonreciprocal behavior, using both optical and acoustic pumping. We have demonstrated that such 'nonreciprocal atoms' can be used to produce complete optical isolation with ultra-low loss over a very compact footprint [5]. Our results also reveal that chiral effects are pervasive throughout the phononic and photonic physical layers of these systems, for instance, showing that chirality can be dynamically imparted to phonon transport to suppress disorder-induced backscattering [6]. This talk will also describe how intuitions drawn from our optomechanical experiments can be used to design practical microwave and acoustic systems with reconfigurable topology and nonreciprocal responses.

*Refreshments will be served before the colloquium*

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