S. W. Hoch

Fiber-cavity-based optomechanical device

We describe an optomechanical device consisting of a fiber-based optical cavity containing a silicon nitride membrane. In comparison with typical free-space cavities, the fiber-cavitys small mode size (10 μm waist, 80 μm length) allows the use of smaller, lighter membranes and increases the cavity-membrane linear coupling to 3 GHz/nm and the quadratic coupling to 20 GHz/nm2. This device is also intrinsically fiber-coupled and uses glass ferrules for passive alignment. These improvements will greatly simplify the use of optomechanical systems, particularly in cryogenic settings. At room temperature, we expect these devices to be able to detect the shot noise of radiation pressure.

Optically mediated hybridization between two mechanical modes.

In this Letter we study a system consisting of two nearly degenerate mechanical modes that couple to a single mode of an optical cavity. We show that this coupling leads to nearly complete (99.5%) hybridization of the two mechanical modes into a bright mode that experiences strong optomechanical interactions and a dark mode that experiences almost no optomechanical interactions. We use this hybridization to transfer energy between the mechanical modes with 40% efficiency.

High-reflectivity, high-Q micromechanical membranes via guided resonances for enhanced optomechanical coupling

Using Fano-type guided resonances (GRs) in photonic crystal (PhC) slab structures, we numerically and experimentally demonstrate optical reflectivity enhancement of high-Q SiNx membrane-type resonators used in membrane-in-the-middle optomechanical (OM) systems. Normal-incidence transmission and mechanical ringdown measurements of 50-nm-thick PhC membranes demonstrate GRs near 1064 nm, leading to a ∼4 × increase in reflectivity while preserving high mechanical Q factors of up to ∼5 × 106. The results would allow improvement of membrane-in-the-middle OM systems by virtue of increased OM coupling, presenting a path towards ground state cooling of such a membrane and observations of related quantum effects.

Multimode optomechanical dynamics in a cavity with avoided crossings

Cavity optomechanics offers powerful methods for controlling optical fields and mechanical motion. A number of proposals have predicted that this control can be extended considerably in devices where multiple cavity modes couple to each other via the motion of a single mechanical oscillator. Here we study the dynamic properties of such a multimode optomechanical device, in which the coupling between cavity modes results from mechanically induced avoided crossings in the cavitys spectrum. Near the avoided crossings we find that the optical spring shows distinct features that arise from the interaction between cavity modes. Precisely at an avoided crossing, we show that the particular form of the optical spring provides a classical analogue of a quantum non-demolition measurement of the intracavity photon number. The mechanical oscillators Brownian motion, an important source of noise in these measurements, is minimized by operating the device at cryogenic temperature (500 mK).

Superfluid Brillouin optomechanics

An optomechanical system made of an optical cavity filled with superfluid liquid helium provides the means to study phenomena involving different degrees of freedom than those in traditional solid-state resonators.

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.

Optomechanics in a fiber cavity

We have built an optomechanical device consisting of a fiber-based optical cavity and a silicon nitride membrane with the goal of observing radiation pressure shot noise and generating squeezed light at room temperature.