Bound states in the continuum are influenced by an external magnetostatic field in hyperbolic material metasurfaces

A bound state in the continuum (BIC) metasurface (MS) was designed to achieve a high quality factor (Q-factor) by utilizing a hyperbolic material (InAs). A unit cell of the MS, comprising four elliptical cylinders and one cylinder, was designed to study the dispersion relationship, Q-factor, and reflection. The amplitude and direction of the external magnetostatic field can be adjusted to influence the frequency and Q-factor of the BIC. The MS structure supports symmetry-protected BICs, which can be converted into quasi-BICs by increasing the incident angle. Further analysis based on multipole theory indicates that the electric dipole (ED) has the most significant influence on the resonance.