Optomechanical readout of an encapsulated micromechanical resonator

Cavity optomechanics is a mature field that has led to the development of ultra-sensitive detectors and has even allowed for the generation of mechanical quantum states at room temperature.  In these coupled systems mechanical motion can be read out from sidebands of the response of a coupled cavity, and a detuned drive can mediate the conversion of photons in a cavity mode and phonons in a coupled mechanical mode, modifying the mechanical mode noise temperature.  Applications of meso-scale resonators such as clocks and resonant sensors could benefit from the cooling achieved using this coupling, as reducing the noise temperature improves sensitivity in resonant sensors and phase noise in oscillators.  However, existing implementation of optomechanics rely on tools such as cryogenic systems or high-power lasers that are challenging to implement in an integrated system.  In this work, we couple an encapsulated micro-scale resonator to an on-chip lumped element resonator built using standard PCB processing. We demonstrate optomechanical readout of the encapsulated high-Q mechanical mode, as well as optomechanical heating and cooling of the mechanical mode that arises due to radiation pressure.