Mode Engineering in Large Arrays of Coupled Plasmonic–Dielectric Nanoantennas

Abstract

Strong electromagnetic field confinement and enhancement can be readily achieved in plasmonic nanoantennas, however, this is considerably more difficult to realize over large areas, which is essential for many applications. Here, dispersion engineering in plasmonic metamaterials is applied to successfully develop and demonstrate a coupled array of plasmonic–dielectric nanoantennas offering an ultrahigh density of electromagnetic hot spots (1011 cm−2) over macroscopic, centimeter scale areas. The hetero‐metamaterial is formed by a highly ordered array of vertically standing plasmonic dipolar antennas with a ZnO gap and fabricated using a scalable electrodeposition technique. It supports a complex modal structure, including guided, surface and gap modes, which offers rich opportunities, frequently beyond the local effective medium theory, with optical properties that can be easily controlled and defined at the fabrication stage. This metamaterial platform can be used in a wide variety of applications, including hot‐electron generation, nanoscale light sources, sensors, as well as nonlinear and memristive devices.

Anapole-Assisted Absorption Engineering in Arrays of Coupled Amorphous Gallium Phosphide Nanodisks

“…In turn, if p x is fixed to 300 nm (Figure d), the variation of p y causes a strong amplification of the anapole-assisted absorption, which peaks at p y = 400 nm. We attribute this phenomenon to grating effects or Rayleigh anomalies, which are well studied for arrays of plasmonic particles with strong dipolar resonances, , showing significant increase of the array extinction once the individual resonance of the particle is merged with the grating resonance. , In rectangular arrays and at normal incidence of light the additional coupling mode arises at the wavelength with n s being the refractive index of the substrate and i , j the grating order. Under this condition, the dipolar fields of the individual particles interfere to form collective oscillations and the in-phase addition of the scattered light fields increases the optical power in the plane of the array. , Even though the resonant particles are dielectric in our study, we observe similar behavior, which we assign to a strong contribution from the ED to the excitation of the anapole state that spectrally overlaps with the TD.…”

“…We attribute this phenomenon to grating effects or Rayleigh anomalies, which are well studied for arrays of plasmonic particles with strong dipolar resonances, 42,43 showing significant increase of the array extinction once the individual resonance of the particle is merged with the grating resonance. 44,45 In rectangular arrays and at normal incidence of light the additional coupling mode arises at the wavelength…”

Recent Progress in the Fabrication and Optical Properties of Nanoporous Anodic Alumina

“…Such broadband and stable photoresponses by highly periodic nanostructures enabled by NAA are not possible in random nanostructures. In a similar recent work, Nasir et al fabricated large arrays of plasmonic-dielectric nanoantennas in the hetero-metamaterials nanostructural forms by longitudinally segmenting Au and ZnO by electrodeposition [303]. The high density of nanopores in NAA was replicated in the generation of electromagnetic hot spots of density ~10 11 cm −2 over a large area.…”

Molecular Plasmonics with Metamaterials

“…Benefiting from the scalable electrochemical fabrication technique, such metamaterials can cover macroscopic (centimeters squared) areas with typical nanorod areal densities as high as 10 10 –10 11 cm –2 . The functionality of nanorod metamaterials can be further extended by inserting functional materials into the nanorods to form split-rod metamaterials , or by coating the surface of the nanorods with functional materials to form core–shell nanorod metamaterials. − The former are usually fabricated via sequential electrodeposition of metal (bottom section), functional material (middle section, e.g., ZnO), and metal (top section) into porous AAO templates on a substrate, and the latter can be readily fabricated by first widening the AAO pores to create a shell around the nanorods with nanometer-scale thickness, followed by the electrodeposition of functional materials such as palladium, polypyrrole, or nickel into the shells, to coat each nanorod. Furthermore, by electrodepositing metal around sacrificial polymer nanorods in a porous AAO template, plasmonic nanotube metamaterials can be fabricated (Figure b). , Coaxial rod-in-a-tube arrays with gap as small as 5 nm can also be realized by sequential deposition of gold nanorods, sacrificial polypyrrole nanoshells, and gold nanoshells into a porous AAO template …”