Wavelength characteristics of gap-variable silicon nanowire waveguide coupler switch using micro actuator

An improved gap-variable silicon nanowire waveguide coupler switch equipped with a micro actuator was designed and its wavelength characteristics were investigated. The coupler switch was assembled on a silicon-on-insulator wafer from an electrostatic comb-drive actuator and two submicron-scale freestanding single-mode waveguides. One waveguide was movable and the other was fixed. The movable waveguide was held by two supporting arms connected to the actuator. When a voltage is applied to the electrodes of the actuator, the gap between the waveguides reduces, allowing light travelling from the input waveguide to transfer to the output. The coupler was symmetrically shaped with respect to the center line between the waveguides to avoid asymmetric electromagnetic distribution. Port isolation of 18.5 dB was obtained at a wavelength of 1.55 μm, and the bandwidth over which the port isolation was higher than-10 dB was approximately 60 nm. These characteristics are suitable for a matrix switch in wavelength-division multiplexing.