Anomalous Optomechanical Damping*

One of the most compelling features of cavity optomechanics is the ability to manipulate the motion of a nanomechanical resonator at the limit imposed by quantum mechanics. For a conventional optomechanical interaction, dynamical backaction between the mechanical and optical degrees of freedom can be used to excite the resonator’s motion for a blue-detuned optical drive, while a red-detuned pump acts to dampen it. Here, however, I will present measurements of an optomechanical device that exhibits anomalous dynamical backaction, with damping on the blue side of the optical resonance and amplification on the red side. We further observe that this amplification effect can be used to induce a parametric instability in the device, driving its motion into self-oscillations, as well as causing hysteretic behavior in the optomechanical damping, spring effect and transmission through the cavity. We look to explain these counterintuitive results by going beyond the standard theory of radiation-pressure-driven optomechanics.