Broad band optical band-reject filters in near-infrared regime utilizing bilayer Ag metasurface

A band-reject filter working in a near-infrared regime employing a bilayer Ag metasurface was demonstrated numerically and experimentally. This band-reject filter exhibited a broad rejection band (more than 500 nm), simple structure (including an ultrathin metal film, a dielectric layer, and substrate), and high tunability in the near-infrared spectral region, superior to previously reported filters with band-reject features. Simulations of optical reflection spectra under different conditions were carried out and revealed that the filtering behavior strongly depends on structural parameters. Three band-reject filters were experimentally fabricated and proved to be in good agreement with simulations.