  We present a design approach for realizing on-chip wavelength division
demultiplexing (WDD) schemes by integrating all-dielectric metasurfaces of TiO2
nanorod arrays into a SiN waveguide. The designed metasurface locally modifies
the effective refractive index of the SiN waveguide, creating an effective WDD
that selectively passes a certain band of wavelengths into a specific output
port. A set of representative 2-channel and 3-channel WDDs schemes were
demonstrated for input TE00/TM00 modes and operating in different bands,
showing the flexibility of our design approach. The proposed WDD schemes are
compatible with visible to infrared wavelengths, photolithography-based
fabrication, high efficiency with maximum transmission of 91%, and a small
footprint at a few microns. Our design method paves the way for realizing
several on-chip integrated devices for applications in optical data processing
and biological sensing.
