Silicon optical add-drop filters with tunable power coupling using MEMS comb drive actuators

Abstract

We develop an optical ring resonator with tunable coupling coefficients for use in wavelength division multiplexing routers. The coupling coefficients of the resonator are precisely tuned by the utilization of an electrostatic comb drive microelectromechanical system (MEMS) actuator. The MEMS actuator has the ability to accurately adjust gap spacing between cavity and waveguide. Moreover, integration of MEMS actuator with optical ring resonators overcomes the optical lithography challenges for patterning the small gap between cavity and waveguide. Different finite-element (FE) method simulations have been carried out in order to study the mechanical and optical operating characteristics of the ring resonator. The movable microring resonator can be displaced 1.33 μm with less than 3 V actuation voltage in 850 μs to control the transferred optical power and bandwidth of the resonator. Optical simulations show extinction ratios as high as 17 dB for the device with 90-nm gap spacing and 21.5 dB for the device with 60-nm gap spacing, respectively. In addition, the bandwidth of the filter is adjustable from 0.3 to 0.65 nm.