Fano-resonance-assisted metasurface for color routing

Controlling the phase of an electromagnetic field using plasmonic nanostructures provides a versatile way to manipulate light at the nanoscale. Broadband phase modulation has been demonstrated using inhomogeneous metasurfaces with different geometries; however, for many applications such as filtering, hyperspectral imaging and color holography, narrowband frequecy selectivity is a key functionality. In this work, we demonstrate, both theoretically and experimentally, a narrowband metasurface that relies on Fano resonances to control the propagation of light. By geometrically tuning the sub-radiant modes with respect to a fixed super-radiant resonance, we can create a phase modulation along the surface within a narrow spectral range. The resulting anomalous reflection measured for such a Fano-resonant metasurface exhibits a 100 nm bandwidth and a color routing efficiency of up to 81% at a central wavelength of λ=750 nm. The design flexibility provided by this Fano-assisted metasurface for color-selective light manipulation is further illustrated by demonstrating a highly directional color-routing effect between two channels, at λ=532 and 660 nm, without any crosstalk.