Enhanced Chiroptical Responses of Chiral Nanocubes Coupled to Periodic Nanopore Arrays

Abstract

Translating highly localized nanoscale chirality into uniform far-field chiroptical emission at the macroscopic scale remains a formidable challenge due to the severe radiative damping and spatially incoherent near-field scattering inherent to isolated nanostructures. Here, we experimentally and theoretically demonstrate a general strategy to generate enhanced and highly uniform chiral emission within the measured momentum space by synergizing discrete chiral nanoparticles with localized cavity-like regions within a periodic lattice. Deviating from conventional chiral nanoparticle arrays, we strategically embed individual and inter-cavity dimer chiral Au nanocubes within a periodic gold nanopore lattice. This architecture triggers a robust hybridization between localized surface plasmon resonances (LSPRs) and lattice-mediated collective modes of the periodic structure. The sub-wavelength nanopore acts as a localized cavity-like region, efficiently coupling and concentrating delocalized lattice energy, thereby amplifying the near-field chiroptical asymmetry. Remarkably, introducing an inter-cavity dimer configuration induces a long-range multipolar coupling, leading to a reconfiguration of the hybridized modes, which is strongly correlated with the observed polarity reversal of the far-field anisotropy g-factor. Furthermore, utilizing momentum-space Stokes polarimetry, we provide evidence for a lattice-mediated collective polarization coherence, where the chaotic near-field asymmetry is successfully converted into a highly uniform angular distribution of circular polarization. This work provides a viable route to bridge the scale mismatch between nanoscale intrinsic chirality and far-field optical performance, providing a viable route for engineering planar chiral emission platforms and spin-dependent planar nanophotonic devices.