The long photon lifetime, strong field confinement, and in-plane emission characteristics make whispering gallery microcavities promising candidates for enhancing light-matter interactions on a chip, ranging from fundamental studies to applied photonics. This talk focuses on optomechanical interaction which enables not only high-precision measurement of mass, force and displacement, but also precise manipulation of the mechanical motion, for example, cooling and amplification of the mechanical motion. In the first part, we propose to dynamically control the cavity dissipation within the strong optomechanical coupling regime, which is able to significantly accelerate the cooling process while strongly suppressing the heating noise. The dynamic control is also capable of overcoming quantum backaction and reducing the cooling limit by several orders of magnitude. In the second part, we demonstrate that the nonlinear optomechanical interaction leads to parametric down-conversion, capable of generating polariton pairs formed by photons and phonons. The nonlinearity is resonantly enhanced through frequency matching, and such parametric down-conversion does not require the stringent condition that the single-photon optomechanical coupling strength be on the order of the mechanical resonance frequency.
References: [1] Y.-C. Liu et al., Phys. Rev. Lett. 111(8), 083601 (2013); [2] Y.-C. Liu et al., Phys. Rev. Lett. 110(15), 153606 (2013).