CM-AMO Seminar | Optomechanics Approaching the Quantum Regime: Exploiting the Mechanical Properties of Light

Speaker: Jack Sankey Physics Faculty Candidate (Postdoctoral Associate, Yale)

A major goal in optomechanics is to observe and control quantum behavior in a system consisting of a solid mechanical element coupled to an optical cavity. Work toward this goal has traditionally focused on increasing the strength of this coupling; however, the form of the coupling is crucial in determining what phenomena are observable.

Here I will show that avoided crossings in the spectrum of an optical cavity containing a flexible dielectric membrane allow us to realize both linear and nonlinear optomechanical coupling. These include cavity detunings that are (to lowest order) linear, quadratic, or quartic in the membrane's displacement, and a cavity finesse that is linear in (or independent of) the membrane's displacement. All the couplings are realized in a single device with extremely low optical loss and can be tuned over a wide range in situ; in particular, we find that the quadratic coupling can be increased three orders of magnitude beyond previous devices. As a result of these advances, the device presented here should be capable of demonstrating the quantization of the membrane's mechanical energy.

I will also discuss our recent efforts to laser cool the membrane's vibrations into the quantum regime. By coupling free-space laser light from room temperature into a 300 mK cryostat we have cooled the membrane's motion from a phonon occupancy of 30,000 to roughly 10. Using a recently-implemented heterodyne measurement we hope to both observe quantum behavior in the membrane's motion and measure a phonon occupancy close to zero.