Broken symmetry theta-shaped dielectric arrays for a high Q-factor Fano resonance with anapole excitation and magnetic field tunability

We have designed and numerically analyzed the theta-shaped dielectric arrays based on a single resonator per unit cell and generated non-radiative anapole resonance with an enhanced Q-factor. Relying on breaking the symmetry, it is shown that instead of leading to additional radiation losses, the Q-factor in theta-shaped Si arrays is enlarged about one order larger than that of the perfect disk arrays. And the magnetic near-field enhancements can be extended outside of the structures and are extremely enlarged. Further, the asymmetrirc magnetic field distributions can be observed by changing the nanorod position, providing a new way of indirectly manipulating the localized magnetic fields. The high Q-factor and strong magnetic near-field enhancements outside of the structures can be easily tailored by adjusting different geometric parameters and are achieved simultaneously, which furthermore provides a useful insight into their tuning behavior.