A three-dimensional optomechanical system for experiments in the quantum limit

At low temperatures, microwave cavities are often preferred for the readout and control of a variety of systems. In this work, we present design and measurements of two independent mechanical resonator device coupled to a 3-dimensional rectangular waveguide cavity. We show that with a suitable modification to the electromagnetic field corresponding to the fundamental mode of the cavity, achieved by coupling a mechanical resonator, the circuit parasitic capacitance can be reduced significantly to as low as 13.7 fF. We perform measurements in the optomechanically-induced absorption (OMIA) regime on both the mechanical resonators, and demonstrate a single photon coupling strength of 12.5 Hz and a cooperativity of 40 for each mode. In addition, utilizing a low-impedance environment between the two-halves of the cavity, our design has the flexibility of incorporating a DC bias across the mechanical resonator which is often a desired feature in tunable optomechanical devices. With further improvements in device parameters, this system has the potential to reach the strong-coupling regime, enabling a wide range of quantum optomechanical experiments.