Toward Room-Temperature Mechanical Motion Driven by Quantum Radiation Force Noise.

We present progress toward building an optomechanical system where the motion of a “trampoline” mechanical device is dominated by the quantum radiation force noise (QRFN) of laser light circulating in a 50 microns-long fiber cavity. The cavity comprises two highly reflective fiber mirrors, achieving finesse ~10,000, and a 100-nm-thin silicon nitride “trampoline” mechanical device is mounted in the middle, such that it feels the “kicks” from photons circulating in the cavity. As of October, the cavity is assembled at UHV and “trampoline” mechanical performance is characterized. Due to the trampoline’s large Brownian motion, we apply radiation force feedback to damp the fundamental mode, which is sufficient to allow us to lock the cavity resonance to the laser frequency. Currently our measurements are limited by thermal intermodulation noise (TIN) in the system, and we will discuss our approaches to mitigate this; if successful, our system will provide access to measurement near the standard quantum limit and generation of broadband optomechanically squeezed light at room temperature.