Optomechanics with Ultra-high-Q Perimeter Modes

Stressed mechanical resonators exhibit dissipation dilution, where the dissipation of their flexural modes is orders of magnitude lower than the intrinsic material loss. Structures with strong dissipation dilution typically utilize cascaded elements, requiring extreme aspect ratios which are difficult to fabricate and integrate with optical cavities. We demonstrate a new type of resonator: polygon-shaped resonators tethered at their vertices. Modes on the perimeter of the polygon exhibit strong dissipation dilution due to the periodicity of the structure, thereby allowing ultra-low loss in compact devices. We realize perimeter modes with Q of 3.6 billion at room temperature with spatial extent of only two acoustic wavelengths, exceeding state-of-the-art mechanical Q by a factor of four in ten times smaller devices. We demonstrate near-field optomechanical coupling between these resonators and photonic crystal micro-cavities in an integrated platform. Our optomechanical transducer has an optomechanical cooperativity above unity with mechanical Q exceeding 150 million at room temperature. Our system is ideally suited for room temperature quantum optomechanics experiments such as feedback cooling to the ground state and ponderomotive squeezing.