Symmetric Meta‐Absorber‐Induced Superchirality

Abstract

Chiral light‐matter interaction in plasmonic metamaterials represents a new paradigm in optics. However, most previously reported works require structural chirality based on asymmetric three‐dimensional architectures, imposing a significant cost barrier in scalable manufacturing. Here, the generation of superchiral light‐matter interaction in symmetric metal‐dielectric‐metal (MDM) metamaterial structures is theoretically proposed. Due to the interplay of the spatially separated and enhanced electric (E‐) and magnetic (H‐) fields with complementary profiles, a superchiral localized hotspot can be generated in MDM structures when an appropriate phase condition is satisfied. By introducing chiral molecules into the spacer layer, the circular dichroism (CD) signal of the coupled system can be enhanced significantly. The origin of the enhanced CD is attributed to the inherent and induced CD signals of the coupled system, which are derived from the direct molecular CD response and the asymmetric absorption of circularly polarized light by the metallic nanostructure. It is demonstrated that the metamaterial‐induced CD response contributes dominantly to the overall CD response of the coupled system, and a 1300‐fold enhancement factor can be obtained when on‐resonance chiral molecules are adsorbed in the optical superchiral field in the spacer layer. This finding paves the way toward the development of practical and scalable platforms for new chiroptical applications.

Enhanced Chiral Mie Scattering by a Dielectric Sphere within a Superchiral Light Field

“…The optical antenna theory can be used to design the chiral light [7]. Symmetric metal-dielectric-metal (MDM) metamaterial structures have also been proposed to enhance the chiral light-matter interaction [8]. However, metals have intrinsic loss, which fundamentally limits the practical performance of the designed plasmonic structures.…”

Uniform Chiral Near‐Fields in Achiral Nanocavity Induced by Magnetic Polaritons Mode

“…In layerby-layer nanostructures, left-handed chiral near-field is obtained in the gap, whereas right-handed chiral near-fields occur in the surrounding medium. [27] The strong enhancement area of chiral near-field locates at the layer between the two nanostructure layers. Unfortunately, these strongly enhanced chiral fields are difficult to use in chiral molecule sensors.…”

Surface Enhanced Circular Dichroism by Electric and Magnetic Dipole Resonance of Cross Shaped Nanoholes

“…At the beginning, the chiral plasmonic nanostructures were considered as potential candidates for enhancing the MCD, because chiral nanostructure can enhance localized optical chiral field which contributes to the MCD [7][8][9] . But lateral studies show that the ICD arisen from interactions of chiral molecule and achiral nanostructure is greater than MCD enhanced by localized optical chiral field [10][11][12][13][14][15][16][17][18][19] . Different shapes of achiral nanostructures, such as half sphere [10][11][12] , cross [13] , cubic [14,15] and cylindrical [16,17] ones have been proposed for enhancing the ICD.…”

“…Although the adjustment of shape and materials indeed enhances the ICD, but no detailed investigation about mechansim of MCD and ICD generation is availble, moreover the enhancement factor still does not meet the expectations. Only an enhancement of MCD up to two orders of magnitude in long wave infrared (LW-IR) range [18] has been reported, but LW-IR range is not comparable with molecular vibrational wavelength, therefore the value of ICD is small. 3 Generally, ICD is larger in the region close to molecular vibrational resonance.…”