Multiple magnetic dipole excitation in permittivity-asymmetric all-dielectric metamaterials induced by quasi-bound states in the continuum

In this work, we numerically investigate multiple magnetic dipole (MD) excitation in an all-dielectric metamaterial of permittivity-asymmetric nanodisk dimer with symmetric geometric parameters. Besides the original MD mode, the permittivity-asymmetric metamaterials can support symmetry-protected dual quasi-bound states in the continuum (BICs), which show inverse square dependence of Q-factors on the asymmetric parameter. Far-field multiple decompositions and magnetic near-field enhancements further indicate that such two quasi-BICs are governed by MD responses, where asymmetric localized MD distributions in near-infrared wavelength realize indirectly manipulate the localized magnetic field. Further, multiple MDs with high Q-factors are designed as a multiwavelength sensor with a near theoretical FOM of similar to 2300.