High-<i>Q</i> All-Dielectric Metasurface: Super and Suppressed Optical Absorption

Abstract

All-dielectric metasurface absorbers are good candidates for realizing near-unity light absorption within subwavelength-thin nanostructures. However, only moderate quality factor (Q-factor, e.g., Q ∼ 10) all-dielectric metasurface absorbers have been demonstrated due to high radiative loss of the supported Mie resonances. Here, we theoretically propose a high-Q crystalline silicon metasurface superabsorber with near-unity absorption in the near-infrared region by utilizing the dipole quasi bound states in the continuum (quasi-BIC) resonances with engineered radiative loss. The designed all-dielectric metasurface superabsorber shows high-Q (∼640) near-unity absorption in the near-infrared region. Moreover, when the superstrate refractive index is different from that of the substrate, the anticrossing behavior of the induced dipole quasi-BIC resonances can be observed in the absorption spectra. This design applies to arbitrary high-refractive-index low-loss materials at various working bands, enabling practical applications of high-Q all-dielectric ultrathin superabsorbers in optical sensing, optical filtering, and photon detection.