Abstract
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 ${\lt}19\;\;{\rm{dB}}$, and cross talk (XT) of ${{\lt}- 15.85\;\;{\rm{dB}}}$ within the span of 1400–1700 nm and coupling length of 4.62 µm are achieved. In addition, ${{\rm{TM}}_0} {-} {{\rm{TE}}_0}$ conversion loss of ${\sim}0.19\;{\rm{dB}}$, ER of 35.88 dB, and XT of ${-}{30.46}\;{\rm{dB}}$ 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 ${\pm}10\;\;{\rm{nm}}$. 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.
© 2022 Optica Publishing Group
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