Broadband Silicon Four-Mode (De)Multiplexer Using Subwavelength Grating-Assisted Triple-Waveguide Couplers

A broadband silicon four-mode (de)multiplexer [(De)MUX] is proposed and experimentally demonstrated based on subwavelength gratings (SWGs)-assisted triple-waveguide couplers (TWCs), which can (de)multiplex TE
₀
, TE
₁
, TE
₂
, and TE
₃
modes. The mode interaction is enhanced, benefitting from both the triple-waveguide coupling and subwavelength structures. The proposed four-mode (De)MUX is composed of three SWG-assisted TWCs connected by three linear tapers. The experimental results show that the 3-dB bandwidths are 100 nm, 76 nm, 90 nm, and 95 nm for the TE
₀
, TE
₁
, TE
₂
, and TE
₃
modes, respectively. The corresponding insertion losses are 0.2, 1.8, 1.3, and 1.7 dB, and the mode crosstalks are -23.3, -17.7, -15.5, and -17.0 dB at the 1550 nm wavelength. The proposed device can work as a mode-(De)MUX compatible with wavelength division multiplexing (WDM) to increase the transmission capacity of on-chip optical interconnects.