Low-Loss and Power-Efficient Polarization-Diversity 4 × 4 Microring Switch on a Multi-Layer Si₃N₄-on-SOI Platform

Silicon optical switches show great potential in building the next generation of flexible switching nodes. However, due to the birefringence nature of silicon waveguides, most of them are polarization sensitive, which significantly affects their practical applications. Here, we demonstrate an integrated polarization-diversity crossbar optical switch on a multi-layer Si<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>-on-SOI platform, capable of handling random polarization states. The optical switch demonstrates exceptional performance, with fiber-to-fiber insertion losses ranging from 4.16 to 6.59 dB and polarization-dependent losses from 0.32 to 1.88 dB. The transmission spectra exhibit a box-like shape with an optical bandwidth of ∼52 GHz and crosstalk below −32 dB. Furthermore, the power consumption of a single switch element is reduced to 46 mW by removing the silicon substrate under the phase shifter, which is only 1/8 of our previous work without undercuts. This research provides strong proof for the practical application of optical switches in optical communication systems.