Design of polarization-independent adiabatic splitters fabricated on silicon-on-insulator substrates

A novel design for a polarization-independent SOI-based 2 × 2 3-dB adiabatic splitter with sub-micron-scale dimensions is proposed and modeled. To achieve slow and smooth mode evolution, a structure with simultaneous tapering of velocity and coupling is used. To reduce the adiabatic region length by adjusting the gap separation, the coupling strengths of TE and TM polarizations as a function of the gap value are analyzed. For both polarizations, a high uniformity within ± 0.2dB over a broad bandwidth from 1520 to 1650 nm is achieved with a 300-μm-long adiabatic region.