arXiv subjects

C. D. Brown

Publications and source records attributed to C. D. Brown.

5 recordsLinked to original sources

arXiv2023

Superfluid Helium Drops Levitated in High Vacuum

We demonstrate the trapping of millimeter-scale superfluid Helium drops in high vacuum. The drops are sufficiently isolated that they remain trapped indefinitely, cool by evaporation to 330 mK, and exhibit mechanical damping that is limited by internal processes. The drops are also shown to host optical whispering gallery modes. The approach described here combines the advantages of multiple techniques, and should offer access to new experimental regimes of cold chemistry, superfluid physics, and optomechanics.

cond-mat.other↗

arXiv2017

Quantum optomechanics in a liquid

Optomechanical systems provide a means for studying and controlling quantum effects in the motion of macroscopic objects. To date, quantum optomechanical effects have been studied in objects made from solids and gases. Here we describe measurements of quantum behavior in the vibrations of a liquid body. Specifically, we monitor the fluctuations of an individual acoustic standing wave in superfluid liquid helium, and find that it displays the characteristic signatures of zero-point motion and measurement back-action. This opens the possibility of exploiting the properties of liquids in general (and superfluid helium in particular) to access qualitatively new regimes of quantum optomechanics.

physics.optics↗

arXiv2017

Cavity Optomechanics in a Levitated Helium Drop

We describe a proposal for a new type of optomechanical system based on a drop of liquid helium that is magnetically levitated in vacuum. In the proposed device, the drop would serve three roles: its optical whispering gallery modes would provide the optical cavity, its surface vibrations would constitute the mechanical element, and evaporation of He atoms from its surface would provide continuous refrigeration. We analyze the feasibility of such a system in light of previous experimental demonstrations of its essential components: magnetic levitation of mm-scale and cm-scale drops of liquid He, evaporative cooling of He droplets in vacuum, and coupling to high-quality optical whispering gallery modes in a wide range of liquids. We find that the combination of these features could result in a device that approaches the single-photon strong coupling regime, due to the high optical quality factors attainable at low temperatures. Moreover, the system offers a unique opportunity to use optical techniques to study the motion of a superfluid that is freely levitating in vacuum (in the case of $^{4}\mathrm {He}$). Alternatively, for a normal fluid drop of $^3 \mathrm{He}$, we propose to exploit the coupling between the drop's rotations and vibrations to perform quantum non-demolition measurements of angular momentum.

quant-ph↗

arXiv2016

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

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.

physics.optics↗

arXiv2016

Superfluid Brillouin Optomechanics

Optomechanical systems couple an electromagnetic cavity to a mechanical resonator which is typically formed from a solid object. The range of phenomena accessible to these systems depends on the properties of the mechanical resonator and on the manner in which it couples to the cavity fields. In both respects, a mechanical resonator formed from superfluid liquid helium offers several appealing features: low electromagnetic absorption, high thermal conductivity, vanishing viscosity, well-understood mechanical loss, and in situ alignment with cryogenic cavities. In addition, it offers degrees of freedom that differ qualitatively from those of a solid. Here, we describe an optomechanical system consisting of a miniature optical cavity filled with superfluid helium. The cavity mirrors define optical and mechanical modes with near-perfect overlap, resulting in an optomechanical coupling rate ~3 kHz. This coupling is used to drive the superfluid; it is also used to observe the superfluid's thermal motion, resolving a mean phonon number as low as 11.

physics.optics↗