Toroidic and antitoroidic orders in hexagonal arrays of dielectric trimers: Magnetic group approach

Article

关键词: SYMMETRY;    METASURFACES;    RESONATORS;    MOMENTS;    STATES;    MODES;   

DOI  :  10.1103/PhysRevB.103.165402

来源: SCIE

【 摘 要 】

Herein, we investigate symmetry-protected toroidal dipole resonances and conditions of their excitation in a new type of electromagnetic metamaterials. These metamaterials are all-dielectric planar periodic arrays of dielectric disks disposed on a dielectric substrate. The elementary building blocks of the array are trimers which are distributed in hexagonal unit supercells. The highest geometrical symmetry of the unit supercell is C-6v. The analysis is fulfilled by using the representation theory of groups with application of the magnetic group theory, which is a new approach in solving such problems. We have shown that to get access to the toroidal supermodes of the array, the symmetry of the unit supercell must be broken twice: firstly, the C-3(v) symmetry of the trimer, and secondly, the C-6v symmetry of the unit supercell needs to be reduced. Selection rules for the symmetric and antisymmetric orders of the toroidal dipole moments in the arrays are defined. In particular, we have shown that with the reduction of the unit supercell symmetry to the C-2(v) group, the array exhibits the toroidal dipole resonance with antitoroidic order. The arrays with the lower C-s symmetry can provide resonances with both toroidic and antitoroidic orders. It is also shown that these arrays are always polarization sensitive. Full-wave simulations and experiments confirm the theoretical predictions. The suggested metamaterials can provide an enhanced light-matter interaction due to the spatially and temporally confined light in resonant systems with very high quality factors.

【 授权许可】

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