3D Chiral MetaCrystals

Abstract

Fine control of the chiral light-matter interaction at the nanoscale, by exploiting designed metamaterial architecture, represents a cutting-edge craft in the field of biosensing, quantum, and classic nanophotonics. Recently, artificially engineered 3D nanohelices demonstrate programmable wide chiroptical properties by tuning materials and architecture, but fundamental diffractive aspects that are at the origin of chiral resonances still remain elusive. Here, a novel concept of a 3D chiral metacrystal, where the chiroptical properties are finely tuned by in-plane and out-of-plane diffractive coupling, is proposed. Different chiral dipolar modes can be excited along the helix arms, generating far field optical resonances and radiation pattern with in-plane side lobes, and suggesting that a combination of efficient dipole excitation and diffractive coupling matching controls the collective oscillations among the neighbor helices. The proposed concept of compact chiral metacrystal can be suitable for integration with quantum emitters and open perspectives in novel schemes of enantiomeric detection.

Chiral Metasurfaces with Maximum Circular Dichroism Enabled by Out‐of‐Plane Plasmonic System

“…To overcome the limited amount of natural chiroptical effects, chiral metamaterials or metasurfaces, consisting of artificially constructed electromagnetic materials, are capable of providing an extraordinary way to control electromagnetic waves via the spatial structuring of materials. [5][6][7][8][9][10][11][12][13][14][15][16][17] Among them, reflective chiral metasurfaces, also known as chiral absorbers and chiral mirrors, [18,19] are capable of near-perfectly absorbing only one circularly polarized wave whereas reflecting its counterparts without reversing their handedness. Thus, they have drawn enormous attention in recent years due to their fascinating potential in photodetection, [20] meta-hologram, [21][22][23][24] nonlinear optics, [25,26] and photochemistry.…”

Surface Lattice Resonances in 3D Chiral Metacrystals for Plasmonic Sensing

“…The chiral dipoles give rise to collective interactions between neighboring helices, and to a selective extinction of CPL in the visible spectral range, with two opposite CD bands. [25,27] Figure 1c shows the extinction spectra of a 30 × 30 elements array with lattice period (LP) of 460 nm, under illumination with CPL at normal incidence, as collected in different refractive index (n) media, in particular, air (n = 1), DI water (n = 1.3334) and oil (n = 1.518). When measured in air (bottom panel), the extinction spectra show the fingerprints of a chiral LSPR, with a higher extinction for right-handed circularly polarized (RCP) light (matching the handedness of the helices), peaked at 𝜆 RCP = 528 nm.…”

“…[20][21][22][23] NH), as fully 3D nanostructures with chiral shape, exhibit a very large optical activity, even under normal incidence conditions. [24] Indeed, in our recent works we described how ordered arrays of 3D NHs can build up a chiral metacrystal, with resulting chiroptical response ruled out by out-ofplane and in-plane lattice parameters, [25] and how they can work as biomolecule sensing systems. [19] Nevertheless, the generation of c-SLRs in such a metamaterial has not been fully investigated.…”

Emerging Nonplanar van der Waals Nanoarchitectures from 2D Allotropes for Optoelectronics

“…[ 157 ] Even at mesoscale, nanowires with Eshelby twist may have optical activity, as the transmission of circularly polarized light to helix metamaterial designed at the same scale has been shown to be selective. [ 159,160 ] At the same time, spiral nanowires containing screw dislocations, regardless of Eshelby twist, may still exhibit optical activity if the crystal is anisotropic (Figure 8e), and more specifically, the optical activity results from linear anisotropy in two directions (Figure 8h). [ 156 ] Therefore, the dispersion of optical response of topologically twisted vdW nanoarchitectures is designable through the alteration of their spatial dimensions, whereas these properties remain to be explored experimentally.…”