Tunable metamaterial with quantitatively switchable anapole modes via quasi-BIC using two methods

Traditional anapole metamaterials exhibit limited tunability and only support single mode. Herein, we employ two methods to achieve the switch from anapole to dual-anapole in a simple metal-perforated structure. As the asymmetry parameter α increases, the quasi-bound states in the continuum (q-BIC) exhibit characteristics of an anapole mode, and switching between anapole and dual-anapole can be accomplished by altering the polarization mode. Alternatively, by incorporating graphene sheet, this functionality can also be realized at very low Fermi energy levels, and even enable anapole mode switching. Furthermore, the effect of the asymmetry parameter α on the sensing and slow-light properties of metamaterials is examined separately. The metamaterials demonstrate group delays of up to 100 ps and a sensitivity of 189 GHz/RIU. Our proposed tunable anapole metamaterials hold significant potential for applications in biosensing, filtering, and optical switching.