Optomechanics and with superfluid helium films / Observation of superfluid solitons
Speaker: Dr Christopher Baker
Affiliation: University of Queensland
Abstract
Cavity optomechanics focuses on the interaction between confined light and a mechanical degree of freedom. Vibrational modes of superfluid helium-4 are an attractive mechanical element for cavity optomechanics, thanks to their ultra-low dissipation arising from superfluid’s viscosity-free flow. Our approach to superfluid optomechanics is based on nanometer-thick films of superfluid helium which self-assemble on the surface of a microscale optical resonator inside a cryostat. Excitations within the film, known as third sound, manifest as surface thickness waves with a restoring force provided by the van der Waals interaction. These excitations, by changing the amount of superfluid in the optical mode’s evanescent field, modulate the effective path length of the optical cavity, thereby providing a dispersive coupling between the superfluid motion and the light confined inside the optical resonator. Leveraging this optomechanical coupling mechanism, we have previously shown laser-cooling and amplification of the superfluid thermal motion [1], observation of quantized vortex dynamics in a superfluid helium film [2], as well as highly efficient Brillouin lasers [3]. In this talk, I will give a rapid overview of our experimental platform, and present recent developments where we optimize the superfluid fountain-pressure interaction to provide strong dynamical backaction. With this, we show optically-driven regenerative oscillation of a 7 mg effective mass superfluid acoustic mode, with a phonon lasing threshold power of only 3 pW, more than three orders of magnitude below the previous lowest reported value, and corresponding to less than one intracavity photon [4]. I will also show how this superfluid functionality can be packaged into an alignment-free, plug-and-play package requiring only fiber-optic access in a conventional cryostat, through the use of silicon-on-insulator photonic circuits [5].
I will also present recent results on the observation of superfluid optomechanical solitons.
About Physics Seminars
The weekly Physics Seminar series focuses on a broad range of physics research within SMP, along with frequent presentations from visiting researchers. Seminars are usually scheduled for 1.00pm on Tuesdays.
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