Bipolar optical forces in coupled photonic crystal cavities

Due to their high quality (Q) factors, resonance modes of cavities are capable of generating much larger optical gradient forces than waveguide modes. Here we experimentally demonstrate the use of resonance modes of double-coupled one-dimensional photonic crystal cavities to generate bipolar optical forces. Mechanical and thermal detunings of the probe resonance modes of the device are calibrated respectively with a nanoelectromechanical system (NEMS) actuator and a temperature-controlled testing platform. Detuning due to the optomechanical effect is hence decoupled from that of the thermo-optic effect. Pumped by third-order even (odd) mode, one cavity is pulled to (pushed away from) the other cavity by 37.1 nm (11.4 nm).