Electrostatic comb-drive actuators for nanoelectromechanical photonics: theory, design, fabrication, and characterization

Electrostatic actuators offer a method for tuning photonic components using orders of magnitude less power than competing technologies. We consider electrostatic comb drives with dimensions tailored for integration with silicon photonics and study their static and dynamical properties. We extract the spring constant by dynamical measurements, which do not rely on assumptions about the electrical properties and fringing fields. This, in turn, allows measuring the differential capacitance without making assumptions about the mechanical properties. The resulting data set therefore allows for an accurate assessment of the validity of multiple theoretical models available in the literature, and we identify the importance of the stress in the anchor points for an accurate theoretical description. We provide a comb-drive design, which can be directly applied in silicon photonics, where it is suitable for inducing very large phase shifts and other optical effects in nanoelectromechanical reconfigurable photonic circuits. Through measurements we find that our design can reach mechanical frequencies of 2.7 MHz, the highest operating frequency of a comb-drive actuator reported so far, while still retaining useful steady-state displacements.