Broadband ultra-compact polarization splitter–rotator using diagonally overlapped bi-layer architecture

A broadband and ultra-compact polarization splitter–rotator based on diagonally overlapped bi-layer architecture and an asymmetrical directional coupler is proposed on a silicon-on-insulator platform. By leveraging the structure over supermode theory, a 1-dB bandwidth of 220 nm, extinction ratio (ER) of < 19 d B , and cross talk (XT) of < − 15.85 d B within the span of 1400–1700 nm and coupling length of 4.62 µm are achieved. In addition, T M 0 − T E 0 conversion loss of ∼ 0.19 d B , ER of 35.88 dB, and XT of − 30.46 d B can be obtained at 1550 nm. The fabrication tolerances are also analyzed, indicating that the insertion losses remain below 1 dB over 1460–1620 nm in terms of width errors and layer-to-layer misalignments within ± 10 n m . The results show that the proposed device is very suitable to utilize between fibers and for polarization diversity of on-chip systems for broadband operation as well as ultra-compact integration.