Design of an ultra-broadband silicon mode (de)multiplexer

We propose a low-crosstalk and broadband mode (de)multiplexer. It is designed by cascading mode (de)interleavers utilizing silicon waveguide asymmetric Y-junctions. Asymmetric Y-junctions of each stage are modular. For each asymmetric Y-junction, the even (odd) modes of the stem separated from the odd (even) modes evolve into the low-order modes of the wide (narrow) arm by controlling the widths of the two arms, and vice versa. A four-channel mode (de)multiplexer for TE polarization is analyzed as an example. Simulations show the four-channel mode (de)multiplexer pair has a low crosstalk (<−14.1 dB) over a common spectral bandwidth of 280 nm.