Tunable amplification and cooling of a diamond resonator with a microscope

Controlling the dynamics of mechanical resonators is central to many quantum science and metrology applications. Optomechanical control of diamond resonators is attractive owing to diamond's excellent physical properties and its ability to host electronic spins that can be coherently coupled to mechanical motion. Using a confocal microscope, we demonstrate tunable amplification and damping of a diamond nanomechanical resonator's motion. Observation of both normal mode cooling from room temperature to 80K, and amplification into self--oscillations with $60\,\mu\text{W}$ of optical power is observed via waveguide optomechanical readout. This system is promising for quantum spin-optomechanics, as it is predicted to enable optical control of stress-spin coupling with rates of $\sim$ 1 MHz (100 THz) to ground (excited) states of diamond nitrogen vacancy centers.