Abstract
The collective effects in a periodic array of plasmonic double-antenna meta-molecules are studied. We experimentally observe that the collective behavior in this structure substantially differs from the one observed in their single-antenna counterparts. This behavior is explained using an analytical dipole model. We find that in the double-antenna case the effective dipole-dipole interaction is significantly modified and the transverse long-range interaction is suppressed, giving rise to the disappearance of Wood's anomalies. Numerical calculations also show that such suppression of long-range interaction results in an anomalous spatial dispersion of the electric-dipolar mode, making it insensitive to the angle of incidence. In contrast, the quadrupolar mode of the antenna pair experiences strong spatial dispersion. These results show that collective effects in plasmonic metamaterials are very sensitive to the design and topology of meta-molecules. Our findings envision the possibility of suppressing the spatial dispersion effects to weaken the dependence of the metamaterials' response on the incidence angle.
Highlights
The importance of metamaterials operating in the IR and visible domains for various applications, including plasmonics [1], photovoltaics and thermo-photovoltaics [2], and sensing [3, 4, 5, 6] is hard to underestimate
The quadrupolar mode of the antenna pair experiences strong spatial dispersion. These results show that collective effects in plasmonic metamaterials are very sensitive to the design and topology of meta-molecules
To understand the physics underlying the optical properties of double-antenna meta-surface (DAM) and demonstrate the importance of the meta-molecule geometry on the collective response, we use as a reference its well-understood counterpart, which consists of periodically arranged single plasmonic antennas
Summary
The importance of metamaterials operating in the IR and visible domains for various applications, including plasmonics [1], photovoltaics and thermo-photovoltaics [2], and sensing [3, 4, 5, 6] is hard to underestimate For this reason, the metamaterials with a resonant response at optical frequencies have recently attracted significant attention. Collective long-range effects are most strongly manifested at the onset of Bragg diffraction, when the period is comparable to the wavelength and the correlation length effectively diverges. We show that the dipole model can qualitatively describe the experimentally observed anomalous collective response of the meta-surface. These results are confirmed by a rigorous numerical modal matching technique [29].
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