Ultra-broadband multimode 3dB optical power splitter using an adiabatic coupler and a Y-branch

As an essential component of mode division multiplexing (MDM) system, a multimode 3dB power splitter with low loss, high power balance, and low mode crosstalk is highly desired. In this paper, we propose an ultra-broadband on-chip multimode 3dB optical power splitter using an adiabatic coupler and an S-bend based Y-branch. As an example, a splitter for the four-lowest modes of a rib waveguide on silicon on insulator (SOI) platform is designed. Simulation results show that the device exhibits < 0.12dB insertion losses, within ± 0.38dB power imbalances, and < -18.5dB mode crosstalks for the four-lowest modes within a large operating wavelength range of 165 nm (from 1400 nm to 1565 nm). The fabrication tolerance of gap size at the output end of the adiabatic coupler is also analyzed.