Theoretical Investigation of Polarization-Insensitive Multimode Interference Splitters on Silicon-on-Insulator

An ultracompact polarization-insensitive 1times2 multimode interference (MMI) splitter based on silicon-on-insulator is investigated theoretically. The impact of the insulator index on the size of the MMI and the polarization-dependent performance is analyzed. A polarization-insensitive 1times2 MMI splitter of 4 mum by 16.5 mum is shown as an example. Relaxed tolerances on MMI width (> plusmn100 nm) and length (> plusmn0.7 mum) are obtained for both polarizations while the polarization differential loss is kept in range of 0.1 dB and its excess loss is kept below 0.5 dB. In addition, a wide operation wavelength window of 150 nm is obtained for both polarizations as well.