High-Q Absorption in All-Dielectric Photonics Assisted by Metamirrors

High-Q absorption in all-dielectric photonics boosts the fundamental study of light–matter interactions at the nanoscale and has potential applications in biomedical science, nonlinear optics, and thermophotonics. In contrast to the demonstrated high-Q (Q-factors > 105) transmission in non-absorbing all-dielectric photonics, the reported experimental Q-factors in absorbing all-dielectric photonics are extremely limited (Q-factors < 170) due to the challenge of simultaneously engineering radiative and non-radiative losses. Here, we demonstrate a design paradigm for high-Q all-dielectric absorption by combining a weakly absorptive film with a metamirror. The metamirror with dispersive reflection selectively enhances the absorptance in the film around the Fabry–Perot frequency, allowing the realization of high-Q absorption. As a proof of concept, a near-infrared all-dielectric absorber, which consists of a low-loss germanium film and a silicon metamirror with quasi-bound states in the continuum mode, is experimentally demonstrated with a Q-factor of 282 and an absorptance of 66.5%. Engineering Q-factors in absorbing all-dielectric photonics promotes the development of sensing, photodetecting, light-emitting diodes, and thermal emission devices.