Nano-scale optical actuation based on coupled one-dimensional photonic crystal cavities

In this paper, we demonstrate a configuration of optical force actuator based on coupled one-dimensional photonic crystal cavities (1D PCCs). A NEMS structure, which consists of 3 cascaded folded-beam-springs and an electrostatic comb drive, is integrated into the device to finely tune the gap between cavities so that the relation between the cavities' resonance shift and their gap changes can be precisely and straightforwardly characterized. Resonance modes of the cavities are utilized to drive the spring structures, which can generate much larger optical forces than waveguide modes due to their high quality factors. The even resonance mode produces an attractive force, while the odd mode produces a repulsive force. In addition, there is the thermo-optic effect accompanying with the optical forces. Here, a decoupling method is also introduced by calibrating the relations of resonance shift versus gap change with the help of the NEMS and resonance shift versus temperature variation in advance. The experimental results show that one cavity is pulled to (pushed away from) the other cavity by 37.1 nm (11.4 nm) for the optomechanical actuator proposed here. This kind of optical actuator has the potential applications of all-optical circuits in future communication and sensing systems.