Gary Steele

Delft University of Technology (Kavli Institute of Nanoscience)

“Cavity Optomechanics: Detecting and controlling motion with microwave light”

Optomechanics is a field that uses light confined in a cavity to detect and control the motion of a mechanical resonator, potentially even at the quantum level. In this talk, I will discuss experiments we have been doing in Delft with microwave optomechanics, where the “light” in this case consists of photons at microwave frequencies that are confined in superconducting cavities.
In the first, experiment, we use high-quality factor (Q-factor) coplanar waveguide cavities to study the motion of a multilayer graphene drum. We find that these “bottom up” crystalline 2D material membranes have high mechanical Q-factors, up to 220,000, at millikelvin temperatures. Using only microwave light, we drive the motion of the drum with radiation pressure forces, and observe strong backaction between photons and phonons, leading to amplification of microwave signals by the graphene drum and strong optical damping of the motion. Through these measurements, we observe a coupling of light and motion in the graphene device should be close to the quantum limit.

In a second experiment, we explore much bigger membranes made from high-stress silicon nitride, now a millimeter in size, and couple these to the microwave fields confined in a 3D superconducting box. Using a highly coherent coupling to the microwave fields, we perform laser cooling of the 100 kHz motion of the membrane down to a temperature of 35 microKelvin, close to its quantum ground state.