Lattice-induced strong coupling in symmetric and asymmetric split-ring metamaterial arrays

The intrinsic link between surface plasmon modes (eigenmodes) and lattice modes in subwavelength periodic structures is investigated based on the split-ring metamaterial structure. The paper shows that the strong coupling between the eigenmodes and the lattice modes can be achieved by appropriately adjusting the period of the metamaterial structure, and the emergence of new, to the best of our knowledge, modes at low frequencies is observed, resulting in a lower spectral loss of a single hybrid resonance and an increase in its Q factor up to 110. In addition, an asymmetric double-split-ring structure is proposed, and the Fano resonance is excited, giving rise to a spectral line with three resonance valleys. The coupled harmonic-oscillator model is used to interpret the underlying coupling mechanism in lattice-induced transparent systems, which agrees well with our simulation results. This strong-coupling scheme between the lattice and the mixed modes of the metamaterial unit provides a new avenue to modulate lattice-induced transparency, high-Q resonance, and strong-field confinement, which may find applications in the design of ultrasensitive sensors, slow-light devices, as well as multiple frequency absorbers and other fields.