Fourier Control of Air Modes in High‐Q Metasurfaces

Abstract

AbstractDielectric metasurfaces supporting high‐quality factor (high‐Q) resonances, e.g., through bound states in the continuum, have attracted significant interest from the scientific community. Air modes can significantly improve the performance and functionality of metasurfaces, for example, by enhancing mode sensitivity and reducing material absorption. Here, the concept of air‐guided mode resonances with Fourier control of the resonance Q‐factor with a double‐ridge metasurface supporting air modes is introduced and experimentally demonstrated. It is shown that the Q‐factor can be easily Fourier controlled all the way to infinity by adjusting the gap width, and that the energy confinement in air is largely independent of the gap width. As an application example, it is shown that the Q‐factor of air modes is decoupled from material losses, thus allowing a Q‐factor enhancement of up to 12× when compared to conventional (single‐ridge) metasurfaces. This design offers an easy way to control the Q‐factor of air modes, thus opening the possibility of achieving high‐Q in metasurfaces using lossy materials.