The field of optomechanics has progressed rapidly in the past few years from proof-of-principle demonstrations of coupling between optical and mechanical systems to the observation of quantum effects in a handful of these devices. During the same period, connections between optomechanical systems and other AMO systems such as ultracold atoms and diamond NV centers have emerged as promising routes towards controlling quantum information in hybrid systems. In this project, we are working to extend both of these efforts by realizing a new type of optomechanical system capable of reaching the quantum regime while also playing host to cold molecules strongly coupled to an optical cavity. The devices we are building will also be substantially more robust and compact than existing optomechanical devices.
To achieve these goals, we are using high finesse optical cavities filled with superfluid helium. The cavities are formed between a pair of optical fibers. Precision-machined glass ferrules are being used to align the fibers and to contain the superfluid. The mechanical element will be the vibrational modes of the superfluid helium filling the space between the two fibers. This design eliminates all mechanical alignments, and should result in a very stable device. Numerical estimates suggest that this device will provide access to a range of quantum phenomena, including observations of the zero-point motion of the superfluid modes, the generation of squeezed light, and measurements of the quantum back action of an optical displacement measurement. In addition, we are exploring the optomechanical properties of superfluid-vacuum interfaces by filling the cavity only partially with superfluid.
Superfluid helium can play host to a variety of atom-like systems (such as metastable helium dimer moledules and electron bubbles) that can interact with both the optical cavity and the sound waves in the helium. Combining optomechanics with such atom-like systems would greatly enhance the versatility of these devices. We are using these superfluid optomechanical devices to study the quantum limits of measurements, and to produce ultrastable light for use in instruments operating at the quantum limit of sensitivity. This work is also providing valuable training for graduate students in laser optics, cryogenics, low-noise measurements, signal processing, data analysis, and quantum optics. This training will allow them to pursue basic and applied research in a wide variety of settings.
