Ultracompact Polarization-Insensitive 1 × <i>N</i> Silicon-Based Optical Wavelength-Selective Switch by Leveraging I/O Waveguide Spacing Difference

Wavelength-selective switches (WSS) have large potential applications in future high-capacity, low-latency, flexible, and energy-efficient data center optical networks. Here, a novel ultracompact 1 × N polarization-insensitive WSS is proposed on the silicon-on-insulator (SOI) platform. The WSS comprises one input port with a polarizing beam splitter and rotator (PBSR), two identical (M × N + 1) × (M + N) arrayed waveguide gratings (AWGs) cascaded with M 1 × N thermo-optic (TO) switches, and N output ports with polarization combiners. The AWG works as both a demultiplexer and multiplexer to eliminate the center wavelength mismatch induced by fabrication errors and to achieve an ultracompact footprint. The TO switches placed on loopback arms allow for the routing of each wavelength to any one of the N output ports. A new design of leveraging the I/O waveguide spacing difference between the loopback inputs and demultiplexing outputs of AWG is employed to eliminate waveguide crossings in a conventional WSS layout design. In experiment, a 12-channel 400 GHz spacing 1 × 2 WSS with a footprint of 1.67 × 1.7 mm2 is demonstrated. The minimal on-chip loss of 6.8 dB, best extinction ratio of 25 dB, and switching speed of 42 μs are achieved. The measured polarization-dependent loss is <0.5 dB and polarization-dependent wavelength shift is <0.08 nm.