Near-flat top bandpass filter based on non-local resonance in a dielectric metasurface

Localized light matter interaction at a resonant nanostructure facilitates spectrally selective transmission of light, which has led to demonstrations of ultrathin metasurface based optical filters. Unfortunately, due to the nature of Lorentzian spectral line shape in such resonances, it is inevitable to suffer significant spectral crosstalk. In this work, we demonstrate a conceptually new type of spectral filter which exhibits near flat-top bandpass with minimized spectral overlaps. To realize this, we leverage the recent development of non-local resonance in dielectric nanostructure to design a double-layered optical filter with performance comparable to the ideal spectral filters. The designed metasurface shows averaged transmission of more than 90% across the target spectral band and suppressed transmission of less than 10% out of the spectral band.