IQUIST Seminar Series Gaurav Bahl, University of Illinois Urbana-Champaign

Time-reversal symmetry (TRS) is a defining property for photons and phonons propagating in linear stationary media. While such linearity is advantageous from a design perspective, it leaves us vulnerable to many detrimental effects arising from disorder and defects both at the material level and at the system level. In fact, it is necessary to break TRS to produce essential protective devices like isolators and circulators. This talk will describe how fundamental light-sound interactions can be exploited for producing strong TRS-breaking effects in photonics. On this journey, we first frame opto-mechanical interaction physics through the lens of quantum condensed matter analogies, including phonon laser action, cooling, and electromagnetically induced transparency [1,2]. We then discuss how these effects can be leveraged to solve long standing scaling challenges for photonic integrated circuits, especially in support of low-temperature quantum technologies and atom-photonic integrated systems. We present experimental demonstrations of record-setting integrated optical isolators without magneto-optics [3,4], and how we can use the underlying TRS-breaking behavior to enable robust photonic devices that are simply immune to undesirable scattering and defects [5,6].

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