Broadband 1 x 4 Silicon Nitride Photonic Switch Fabricated on a Hybrid Electrothermal and Electrostatic MEMS Platform

This study demonstrates a monolithic 1 x 4 optical switch composed of a planar micro-electro-mechanical system (MEMS) integrated with silicon nitride (SiN) waveguides. The switching motion is induced by an optimized cascaded chevron electrothermal actuator, which produces an analog, precise, and large stroke for low voltages. Nanoscale displacement measurements show a repeatability on the order of 10 nm and a total switching displacement of ∼12 μm for about 10 V. To reduce the insertion losses, a parallel plate electrostatic actuator closes the gap between the waveguides after the switching motion. The optical transmission, measured for 10 devices, is roughly the same across the entire 1520--1620 nm wavelength range. The average optical losses are 4.0 ± 1.9, 4.4 ± 2.0, 4.9 ± 1.9, and 4.1 ± 1.2 dB for ports 1 to 4 respectively, while the average optical crosstalk is smaller than −35 dB. The relatively compact switch (< 1 mm
²
), considering its large displacement, is built on a silicon-on-insulator wafer with a customized fabrication process flow developed by AEPONYX Inc. We believe that this device can lead the way to a new class of small and robust MEMS integrated silicon photonic devices able to operate over a wide wavelength span and to provide a large tuning range for low voltages. Future work will focus on reducing the switch optical losses and on achieving near zero power consumption with the addition of mechanical latches.