Strong, spectrally-tunable chirality in diffractive metasurfaces

León, Israel De; Horton, Matthew; Schulz, Sebastian A.; Upham, Jeremy; Banzer, Peter; Boyd, Robert W.

doi:10.1038/srep13034

Cited by 94 publications

(99 citation statements)

References 40 publications

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“…Extrinsic chirality allows for control over the polarization properties of the transmitted light and optical activity of reflected waves . Spectrally tunable enhanced extrinsic chirality was realized in flat metasurfaces, owing to the interaction of delocalized lattice surface modes with individual resonances, leading to strong narrowband circular dichroism (CD) spectra and spatially coherent circularly polarized fluorescence …”

Section: Introductionmentioning

confidence: 99%

Chirality of Symmetric Resonant Heterostructures

Nechayev

Woźniak

Neugebauer

et al. 2018

Laser & Photonics Reviews

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Chiroptical effects arising in mirror‐symmetric geometrically achiral resonant heterostructures are investigated. It is shown that coalescence of extrinsic chirality, heterogeneous morphology, and substrate‐induced break of symmetry leads to pronounced circular dichroism and circular birefringence. The physics of the involved phenomena is elucidated by studying spin‐splitting in scattering and hybridized dipolar modes of a heterodimer made of gold and silicon nanoparticles of the same shape and size. The work sheds new light on the optical properties of heterogeneous nanostructures and paves the way for designing polarization‐controlled tunable heterogeneous optical elements.

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Section: Introductionmentioning

confidence: 99%

Chirality of Symmetric Resonant Heterostructures

Nechayev

Woźniak

Neugebauer

et al. 2018

Laser & Photonics Reviews

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“…More importantly, because of the design complexity of the proposed chiral patterns and the enhancement mechanism being linked only to the localized mode, it is hard to tailor the chiral resonance by simply altering geometric parameters. [ 41 ] Although some pioneer work [ 35,36 ] on chiral metasurfaces linked the collective chiral responses to the propagating modes, there is still lack of clear demonstration. Consequently, the chiral responses shown in previous works were mostly spectrally fi xed, which severely limits practical applications.…”

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confidence: 99%

A Novel Chiral Metasurface with Controllable Circular Dichroism Induced by Coupling Localized and Propagating Modes

Wang

Adamo

et al. 2016

Advanced Optical Materials

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COMMUNICATIONeither exhibit a weak chiral response or require illuminations at quite shallow angles of incidence. More importantly, because of the design complexity of the proposed chiral patterns and the enhancement mechanism being linked only to the localized mode, it is hard to tailor the chiral resonance by simply altering geometric parameters. [ 41 ] Although some pioneer work [ 35,36 ] on chiral metasurfaces linked the collective chiral responses to the propagating modes, there is still lack of clear demonstration. Consequently, the chiral responses shown in previous works were mostly spectrally fi xed, which severely limits practical applications. [ 5,22 ] In this communication, we study a novel chiral metasurface made of an array of nanoslits milled in a ≈100 nm thin gold layer on a sapphire substrate that exhibits pronounced chiral optical resonant responses from visible to near-IR frequencies which, thanks to the effect of surface lattice resonances [ 42,43 ] introduced by a propagating mode, are fi nely controllable by the tuning of both the lattice period and the length of nanoslits. Our results clearly highlight the impact of the propagating surface plasmon modes in controlling chiral responses in metamaterials and metasurfaces, and therefore, provide a new strategy for designing chiral platforms with tailored responses as needed. Furthermore, when compared to chiral patterns made of isolated metallic nanoparticles, our metamaterial, etched in a continuous metal fi lm, allows electrical conductivity across the fi lm, thus enabling applications for optoelectric devices as well.The proposed chiral pattern, a square lattice metamaterial array with unit cell period p , is illustrated in Figure 1 . Each metamolecule is made of four nanoslits of identical length a and width b separated by a gap g , in a chiral arrangement where each slit has a 90° rotation with respect to the preceding one and is aligned with its long axis to the center of the following one, in either clockwise or anticlockwise rotation, to determine the handedness of the isotropic chiral pattern. Figure 1 b,c shows scanning electron microscope (SEM) images over a magnifi ed area of a 40 × 40 µm 2 metamaterial array (50 × 50 unit cells) for the same sample design with opposite handedness ( a = 350 nm, b = 100 nm, g = 50 nm, p = 810 nm), fabricated by focus ion beam milling of the gold fi lm, while arrays with the same unit cell size and different lattice constant are also prepared.Based on the resonant profi le of a single nanoslit, the chiral confi guration will exhibit overlapping of E-fi eld and H-fi eld hot spots occurring around the four gaps, [ 6,39 ] which means that the localized plasmon mode given by the coupling between adjacent nanoslits in one unit cell contributes to the enhancement of Chirality is a key molecular structural concept and a ubiquitous phenomenon in nature that has become an increasingly signifi cant research avenue since it was introduced in the context of metamaterials. [ 1,2 ] Compared with the weak chiral opt...

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“…A common way for polarization conversion and rotation is the use of wave plates of birefringent materials and optical gratings. An imbalance between the left-and right-circularly polarized photons takes place in chiral materials with nonequivalent left-and right-circularly polarized electromagnetic field modes [1][2][3][4]. The imbalance in semiconductors is usually reached by applying a static magnetic field that disturbs the time-reversal symmetry and leads to a splitting of the left-and right-circularly polarized modes.…”

Section: Introductionmentioning

confidence: 99%

Controlling circular polarization of light emitted by quantum dots using chiral photonic crystal slabs

et al. 2015

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We study the polarization properties of light emitted by quantum dots that are embedded in chiral photonic crystal structures made of achiral planar GaAs waveguides. A modification of the electromagnetic mode structure due to the chiral grating fabricated by partial etching of the waveguide layer has been shown to result in a high circular polarization degree ρ c of the quantum dot emission in the absence of external magnetic field. The physical nature of the phenomenon can be understood in terms of the reciprocity principle taking into account the structural symmetry. At the resonance wavelength, the magnitude of |ρ c | is predicted to exceed 98%. The experimentally achieved value of |ρ c | = 81% is smaller, which is due to the contribution of unpolarized light scattered by grating defects, thus breaking its periodicity. The achieved polarization degree estimated removing the unpolarized nonresonant background from the emission spectra can be estimated to be as high as 96%, close to the theoretical prediction.

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Strong, spectrally-tunable chirality in diffractive metasurfaces

Cited by 94 publications

References 40 publications

Chirality of Symmetric Resonant Heterostructures

Chirality of Symmetric Resonant Heterostructures

A Novel Chiral Metasurface with Controllable Circular Dichroism Induced by Coupling Localized and Propagating Modes

Controlling circular polarization of light emitted by quantum dots using chiral photonic crystal slabs

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