Inverse-Designed Ultra-Compact Polarization Splitter–Rotator in Standard Silicon Photonic Platforms With Large Fabrication Tolerance

Polarization splitter-rotators (PSRs) are crucial components for controlling the polarization states of the input light in photonic integrated circuits. In this paper, we designed, fabricated and characterized a high-performance CMOS-compatible O-band PSR based on silicon-on-insulator (SOI) platform by using inverse design technique. The PSR mainly consists of a polarization rotator designed by our new proposed bi-level shape adjoint method and a mode demultiplexer designed by topology adjoint method. The device robustness against fabrication errors is significantly strengthened by properly designing optimization strategies. The proposed PSR displays a low insertion loss (<1 dB) and low crosstalk (<−20 dB) within a bandwidth of 50 nm by measurements. The device footprint is 3 × 17 μm, making this the smallest PSR based on standard silicon photonic platforms with no extra layers or an air cladding.