Flexible engineering of circular dichroism enabled by chiral surface lattice resonances

Abstract

Engineering the chiroptical responses of artificial nanostructures is vital for realizing applications in the fields of optical devices, enantioselective separation and bio-sensing. Here, by utilizing the nano-kirigami based meta-molecule arrays, the flexible engineering of circular dichroism (CD) is achieved in the near-infrared wavelength region by the excitation of chiral surface lattice resonances (SLRs). It is found that the chiral SLRs can be flexibly tailored by a tiny structural perturbation. As a result, the wavelength, intensity, and sign of CD peak/dip can be abruptly engineered. Specifically, a CD peak with the value of +0.44 is evolved into a CD dip with the intensity of -0.66, when the etching silt length of the meta-molecules is simply decreased by 190 nm. Importantly, such CD reversal is experimentally demonstrated with the nano-kirigami method without requiring the inversion of geometric chirality. Moreover, it is found that the asymmetric dielectric environment around the meta-molecules can significantly suppress the chiral SLRs, providing an insightful understanding of the chiral SLR. Such flexible tailoring of the CD with chiral SLRs paves a versatile way towards the manipulation of chiral light-matter interactions and chiroptical functional devices.

Chiral Lattice Resonances in 2.5-Dimensional Periodic Arrays with Achiral Unit Cells

“…The prospects of these applications have triggered the study and characterization of a variety of periodic arrays supporting chiral lattice resonances. − The majority of these arrays are built from the repetition of chiral unit cells, made of either individual nanostructures with complex chiral morphologies, − , such as helices, or multiple nanostructures forming a chiral arrangement. , As expected, the lattice resonances supported by these systems exhibit different responses under illumination with right- and left-handed circularly polarized light. More recently, it has been shown that the combination of a rectangular lattice with an achiral unit cell results in arrays capable of supporting lattice resonances with some degree of chirality, which can be enhanced by positioning the array in an inhomogeneous dielectric environment .…”

“…53−55 The prospects of these applications have triggered the study and characterization of a variety of periodic arrays supporting chiral lattice resonances. 56−64 The majority of these arrays are built from the repetition of chiral unit cells, made of either individual nanostructures with complex chiral morphologies, [56][57][58]63 such as helices, 60 or multiple nanostructures forming a chiral arrangement. 65,66 circularly polarized light.…”

Exploring Functional Photonic Devices made from a Chiral Metal-Organic Framework Material by a Multiscale Computational Method

“…To explain the emergence of lattice resonances and the characterization of the collective coupling of multipoles inside a lattice, see [66,67], for instance. The asymmetric Fano resonance observed in this spectral range in the circular dichroism spectra indicates an interference of different competing pathways determining whether the lattice resonance is left-or right-handed and, therefore, also the sign of the circular dichroism, see [61]. Three aspects influence the resonance around 334 nm in the spectra: (i) The chiral response of the MOF material, (ii) the chiral, electric, and magnetic dipole moments of the isolated MOF cylinders, and (iii) the lattice coupling.…”

“…The possibility of enhancing the circular dichroism of chiral objects by the strong near-fields of plasmonic structures or high-refractive-index dielectric materials as silicon cylinders is well-known [53][54][55][56][57][58][59][60][61][62]. A central quantity in the discussion of this enhancement is the optical chirality density defined as [63]…”

“…Especially if the electric and magnetic dipole resonances of the nanostructure overlap, a high enhancement can be achieved [57,58,60]. In this context, also lattice resonances, which collectively couple multipole moments, are of significant importance [59,61,62].…”