Kavli Affiliate: Simon Groblacher
| First 5 Authors: , , , ,
| Summary:
Superfluid helium is a prototypical quantum liquid. As such, it has been a
prominent platform for the study of quantum many body physics. More recently,
the outstanding mechanical and optical properties of superfluid helium, such as
low mechanical dissipation and low optical absorption, have positioned
superfluid helium as a promising material platform in applications ranging from
dark matter and gravitational wave detection to quantum computation. However,
experiments with superfluid helium incur a high barrier to entry as they
require incorporation of complex optical and electrical setups within a
hermetically sealed cryogenic chamber to confine the superfluid. Here, we
report on the design and construction of a helium chamber setup for operation
inside a dilution refrigerator at Millikelvin temperatures, featuring
electrical and optical fiber access. By incorporating an automated gas handling
system, we can precisely control the amount of helium gas inserted into the
chamber, rendering our setup particularly promising for experiments with
superfluid helium thin films, such as superfluid thin film optomechanics. Using
silicon nanophotonic resonators, we demonstrate precise control and in-situ
tuning of the thickness of a superfluid helium film on the sub-nanometer level.
By making use of the exceptional tunability of the superfluid film thickness,
we demonstrate optomechanically induced phonon lasing of phononic crystal
cavity third sound modes in the superfluid film and show that the lasing
threshold crucially depends on the film thickness. The large internal volume of
our chamber (V_chamber = 1l) is adaptable for integration of various optical
and electrical measurement and control techniques. Therefore, our setup
provides a versatile platform for a variety of experiments in fundamental and
applied superfluid helium research.
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