A dual-narrowband perfect absorber based on the magnetic anapole mode with polarization tunability and high...

Due to its unique energy localization and non-radiative properties, the anapole mode has garnered significant attention in dielectric nanostructures. This study proposes a polarization-tunable, high-sensitivity dual-narrowband perfect absorber, comprising Si double disks and an Au ring. Nearly perfect dual-narrowband absorption is achieved, with peak absorptions reaching 98.58% and 99.38%, respectively. Electromagnetic field analysis and multipole decomposition reveal that magnetic dipole response and magnetic anapole mode excitations dominate the two absorption peaks, respectively. By adjusting the structural parameters, the position of the resonance peaks and their absorption characteristics can be effectively modulated. The optical switching effect is realized by tuning the incident light polarization angle. Furthermore, this structure demonstrates exceptional capabilities in refractive index sensing, achieving sensitivities up to 573.6 nm per RIU and 622.1 nm per RIU. This design deepens the understanding of the physical mechanism of the magnetic anapole mode and offers new insights and application prospects for developing high-performance nanophotonic absorbers and refractive index sensors.