Luyao Jiang defends graduate thesis “Nonreciprocal dynamics in a cryogenic optomechanical system”

March 5, 2020

On March 2, 2020 Luyao Jiang successfully defended his thesis: “Nonreciprocal dynamics in a cryogenic optomechanical system” (Advisor: Jack Harris).

Jiang explained “Imagine that you and your friend are chatting on a one-way street of sound, such that you can hear what your friend is saying, but your friend can not get your voice. You may wonder: how is this possible? Can we make some changes so that we can hear each other, or my friend can hear me but not vice versa? My research demonstrates how such asymmetry (specifically, nonreciprocity) may happen and be tuned conveniently in an optomechanical system. Furthermore, we utilized this effect to realize a new form of cooling, in which a cold object may be cooled by a hot object under certain circumstances. “

Jiang will join Wells Fargo.

Thesis AbstractNonreciprocity in various branches of physics has been studied for more than a century, e.g., from classical to quantum mechanics, and from particle to condensed matter. It is particularly interesting to consider nonreciprocal phenomenon in open (non-hermitian) systems. In this dissertation, I use a cryogenic cavity optomechanical system to demonstrate robust nonreciprocal interactions between two phononic resonators. The nonreciprocity, either transient or static, is realized via the cavity mediated optomechanical interaction.

I will start with a pedagogical introduction to nonreciprocity as well as non-hermiticity in physics, followed by a brief review of optomechanics and a theoretical derivation of the nonreciprocity in optomechanical systems. Then I will introduce our experimental realization of the optomechanical system, i.e., the membrane-in-the-middle setup. Next I will present the main result of this dissertation, which includes the experimental demonstration of both transient and static optomechanical nonreciprocity. I will conclude with a discussion of our on-going study of high order exceptional points (the degeneracy in multi-level open systems).