Flat-Top CWDM (De)Multiplexers Based on Contra-Directional Couplers With Subwavelength Gratings

A coarse wavelength division multiplexing (CWDM) (de)multiplexer based on the contra-directional couplers (contra-DCs) with subwavelength grating (SWG) waveguide is proposed and demonstrated on the silicon-on-insulator (SOI) platform. By utilizing the SWG waveguides with strong coupling strength, the coupling length can be significantly reduced and the transmission spectra are flat-top. The footprint of the demonstrated device is about 15 × 160 μm
²
. The proposed device is characterized with large bandwidth and low crosstalk at C-band.