All-dielectric metasurfaces enabled by quasi-BIC for high-Q near-perfect light absorption

All-dielectric metasurface (ADM) absorbers driven by quasi-bound states in the continuum (BIC) are critical for high-performance optoelectronic devices due to their ability to offer high Q-factor absorption. However, these all-dielectric metasurfaces usually require the aid of degenerate critical coupling schemes or back-metal reflective layers to achieve high absorption, which often suffers from limitations such as sensitive geometrical parameters, ohmic losses, and low Q-factors. This work presents an ADM for high-Q near-perfect light absorption, which consists of double Si nanorods and SiO₂/Ta₂O₅ multilayers. By breaking the symmetry of the length of the Si nanorods, this ADM can excite a single quasi-BIC resonance corresponding to the electric dipole. Without introducing a metal layer, we realize the highly asymmetric coupling of quasi-BIC by only 6 layers of SiO₂/Ta₂O₅ films. It is theoretically and numerically demonstrated that the quasi-BIC has more than 98% absorption at 943.68 nm and a Q-factor as high as 2842. In addition, the ADM exhibits excellent tolerance to geometrical parameters while ensuring high absorption performance. Our results provide new ideas for the design of all-dielectric perfect absorbers with large tolerances and high Q-factors and also open up new possibilities for optical filtering, optical sensing, and photon detection devices.