Ultra-broadband 16-channel mode division (de)multiplexer utilizing densely packed bent waveguide arrays

We demonstrate an ultra-broadband 16-channel mode division (de)multiplexer utilizing densely packed bent waveguide arrays (DPBWAs). The phase mismatch is realized by using bent waveguides with a different radius instead of changing the waveguide width. The proposed structure shows theoretical insertion losses (ILs) that are <0.1  dB and crosstalk (CT) that is <-30  dB over a 100 nm wavelength range for all the channels. The fabricated device, which consists of a multiplexer, DPBWAs, and a demultiplexer, exhibits ILs that are <1  dB and crosstalk that is <-20  dB over an ∼80  nm wavelength band.