Superfluid Optomechanics with Nanofluidic Geometries

Research output: ThesisDoctoral Thesis

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Abstract

In this work, a novel implementation of superfluid optomechanics is developed, exploiting nanofluidic confinement within a sonic crystal geometry. The aim of which is to enhance the optomechanical coupling strength while preserving the intrinsic properties of superfluid He-4, via limitation of radiative acoustic effects. These nanostructures are designed and fabricated using cleanroom techniques, with focus on the development of a direct wafer bonding technique. The cleanroom fabricated chips are then integrated into superconducting microwave cavities. For measurements, a dilution refrigerator (capable of mK cooling) was refurbished for modern microwave measurements and work with superfluid He-4. COMSOL Multiphysics simulations are used to design the optomechanical system, both the acoustics of the sonic crystal and the chip-cavity microwave environment. From these simulations a predicted vacuum optomechanical coupling is calculated giving g_0/2pi = 0.63 mHz; between a superfluid mode of frequency 1.34 MHz, and a microwave cavity mode of 4.2 GHz. Phase sensitive homodyne measurements of the chip-cavity system in the presence of He-4 found mechanical signals close to the predicted resonance frequency, however these signals were insufficient in strength or consistency to determine the optomechanical parameters of the system.
Original languageEnglish
QualificationPh.D.
Awarding Institution
  • Royal Holloway, University of London
Supervisors/Advisors
  • Rojas, Xavier, Supervisor
Thesis sponsors
Award date1 Aug 2022
Publisher
Publication statusUnpublished - 11 Jul 2022

Keywords

  • Superfluid
  • Nanofluidics
  • optomechanics
  • Microwave
  • HE-4
  • sonic crystal
  • phononic

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