High-Q triple-mode quasi-bound states in the continuum in an asymmetric dielectric metamaterial

Bound states in the continuum (BICs) in metamaterials have attracted much attention due to their high efficiency in field enhancing. In this paper, we numerically demonstrated the triple-mode symmetry-protected BICs (SP-BICs) in an all-dielectric microtube metamaterial. By moving the hollows transversely and longitudinally in microtubes, three SP-BICs are transformed into high quality-factor (Q-factor) quasi-BICs (q-BICs), which are supported by asymmetric magnetic toroidal dipole electric hexapolar resonances respectively. The maximum Q-factor of q-BICs enabled by asymmetric magnetic toroidal dipole reaches 67647. This high Q-factor triple-mode q-BICs in all-dielectric microtube metamaterial has great potential in the applications of sensing, laser generation, and nonlinear optics.