Noise Thermometry for Macroscopic Cavity Optomechanics*

We are in the phase of developing macroscopic optomechanical systems using superconducting radio frequency (SRF) cylindrical cavities. One of the important steps for optomechanics is observing and calibrating the noise thermometry of the system, in terms of both cavity and mechanical occupation. One such improvement with our optomechanical system includes a capacitive detector and driver placed on the outside of the SRF cavity. This integration allows us to induce motion in the membrane as well as observe the response. Here, we discuss the methods and results for developing a cm-scale optomechanical system. Despite a low vacuum optomechanical coupling coefficient (g₀/2π ≈ 1 × 10⁻⁵ Hz), we anticipate a working structure that provides a platform for future macroscopic optomechanical systems.