Ultra-Compact On-Chip Silicon Photonic Polarization- and Wavelength-Selective Switch

Silicon-based optical switches are indispensable for on-chip optical interconnects and have become essential components of optical neural networks and optical computing. Although broadband Mach–Zehnder interferometer (MZI) switches have been widely studied, they are large in size and difficult to implement wavelength or polarization selection functions at the switching element (SE) level. Here, we introduce a novel design for a polarization- and wavelength-selective switch on the standard silicon-on-insulator (SOI) platform, composed of mode-coupled micro-ring (MR) switches, polarization rotators (PRs), and mode exchangers (MEs). Parallel-cascaded MR switches facilitate the expansion of wavelength channels, while PRs and MEs enable two polarizations to route separately through two sets of MR switches without the need for polarization splitting. As a proof of concept, we demonstrate an ultra-compact 2 × 2 × 3λ × 2P (TE & TM) SE with full spatial, spectral, and polarization switching capabilities. Experimental results show that the insertion losses are less than 1.1 dB, and the crosstalk is better than −17 dB around 1550 nm. Additionally, all channels’ 3 dB optical bandwidth is over 60 GHz, and characterization with 50 Gbps on-off keying (OOK) modulated signals demonstrates aggregate throughput up to 600 Gbps.