Subwavelength, polarimetric color sorting by densely interleaved nano-resonators

Abstract

Sorting light by spectrum in subwavelength scale emerges as important research due to its potential applications in nanoscale optical devices. Diverse research activities are explored to achieve efficient spectral sorting based on nanostructured metasurfaces by leveraging plasmonic and dielectric resonances. While they show many advantages of controlling light in nanoscale with compact form factor, practical realization of the efficient sorting of light in visible spectrum is still elusive due to the strong optical coupling and crosstalk between nanostructures that are arranged in subwavelength scale. Here, we demonstrate silicon-based ultrathin metasurfaces composed of densely interleaved one-dimensional nano-resonators (meta atoms) with three different widths that function both as efficient spectral sorter and light absorber in the visible regime. We find that the geometric aspect ratio of meta atoms and specific mode of resonance play a crucial role in realizing efficient subwavelength spectral splitting with significantly suppressed crosstalk. The sorting efficiency up to 78% is reported by optimally designing the metasurface. We believe that suggested designing scheme paves an important way to realize ultrathin, subwavelength spectral sorters and to develop nano-scale optical sensors.