Equivalent energy level hybridization approach for high-performance metamaterials design

Metamaterials have microscopic physical properties highly analogous to real materials, since their characteristic frequencies behave as equivalent energy levels, providing an efficient route to deal with stacked meta-atoms with strong interactions. Based on the hybridization of equivalent energy levels theory, in this paper, we designed transmissive multilayer metasurfaces to convert the handedness of a circularly polarized wave with high efficiency in a broad bandwidth. In stacked metasurfaces, the equivalent energy levels gradually split with an increasing layer number (i.e. meta-atoms). Their hybridization introduces trapped modes with near-unity transmission, contributes to a near-π transmission phase difference and promotes the split modes overlapping to form a broad bandwidth. Through theoretical calculations, numerical simulations and experimental measurements, a four-layer metasurface was shown to exhibit a high transmission conversion coefficient (80-98%) of a circularly polarized wave covering the whole X-band. Furthermore, a multifunctional meta-lens with broad bandwidth was designed and fabricated based on the Pancharatnam-Berry phase to converge or diverge incident Gaussian beams with different handedness at a high efficiency rate.

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