Photothermal optomechanics in superfluid helium coupled to a fiber-based cavity

TL;DR

This paper investigates how acoustic modes in superfluid helium interact with a fiber-based optical cavity, revealing that the coupling is mainly driven by photothermal effects and depends on device geometry.

Contribution

It introduces a framework for understanding superfluid helium acoustic modes coupled to fiber cavities, emphasizing photothermal optomechanical interactions.

Findings

Acoustic modes depend on device geometry.

Optomechanical coupling is predominantly photothermal.

Acoustic modes observed via optomechanically induced transparency.

Abstract

Presented in this paper are measurements of an optomechanical device in which various acoustic modes of a sample of superfluid helium couple to a fiber-based optical cavity. In contrast with recent work on the paraxial acoustic mode confined by the cavity mirrors, we focus specifically on the acoustic modes associated with the helium surrounding the cavity. This paper provides a framework for understanding how the acoustic modes depend on device geometry. The acoustic modes are observed using the technique of optomechanically induced transparency/amplification. The optomechanical coupling to these modes is found to be predominantly photothermal.