Actuation of micro-optomechanical systems via cavity-enhanced optical dipole forces

Optical forces can produce significant mechanical effects in micro- and nanophotonic systems. Here we demonstrate a novel optomechanical system using a movable, micrometre-scale waveguide evanescently coupled to a high-Q optical microresonator. Micrometre-scale displacements of the waveguide are observed for milliwatt-level optical input powers. Measurement of the spatial variation of the force on the waveguide indicates that it arises from a cavity-enhanced optical dipole force resulting from the stored optical field of the resonator. This force is used to realize an all-optical tunable filter operating with submilliwatt control power. A theoretical model of the system shows that the maximum achievable force is independent of the intrinsic Q of the optical resonator and scales inversely with the cavity mode volume, suggesting that such forces may become even more effective as devices approach the nanoscale.