Chiroptical Effects in Planar Achiral Plasmonic Oriented Nanohole Arrays

Maoz, Ben M.; Ben-Moshe, Assaf; Vestler, Daniel; Bar-Elli, Omri; Markovich, Gil

doi:10.1021/nl300316f

Cited by 92 publications

(91 citation statements)

References 28 publications

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“…For instance, Ben et aldemonstrated a ~4 times stronger optical chirality in achiral periodic nanoholes compared to the gammadion structure. 12 Recently, Abraham et. al.…”

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confidence: 99%

Switching the Optical Chirality in Magnetoplasmonic Metasurfaces Using Applied Magnetic Fields

et al. 2020

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Chiral nanophotonic devices are promising candidates for chiral molecules sensing, polarization diverse nanophotonics and display technologies. Active chiral nanophotonic devices, where the optical chirality can be controlled by an external stimulus has triggered great research interest.However, efficient modulation of the optical chirality has been challenging. Here, we demonstrate switching of the extrinsic chirality by applied magnetic fields in a magneto-plasmonic metasurface device based on a magneto-optical oxide material, Ce1Y2Fe5O12 (Ce:YIG). Thanks to the low optical loss and strong magneto-optical effect of Ce:YIG, we experimentally demonstrated a giant and continuous far-field circular dichroism (CD) modulation by applied magnetic fields from -0.65° to +1.9° at 950 nm wavelength under glancing incident conditions. The far field CD modulation is due to both magneto-optical circular dichroism and near-field modulation of the superchiral fields by applied magnetic fields. Finally, we demonstrate magnetic field tunable chiral imaging in millimeter-scale magneto-plasmonic metasurfaces fabricated using self-assembly. Our results 2 provide a new way for achieving planar integrated, large-scale and active chiral metasurfaces for polarization diverse nanophotonics. KEYWORDS: Magnetoplasmonic, Metasurface, Optical Chirality, Magneto-optical effectChirality describes the symmetry property of a structure, that its mirror image cannot be superimposed with itself through translation and rotation operations, like our two hands. The chirality of biomolecules is universal in our living body, such as amino acid and proteins, which has significance in biomolecules recognition. 1,2 However, the chiroptical signal of chiral biomolecules is very weak. Recently, chiral plasmonic 3,4 and all dielectric structures 5,6 with large chiroptical response have attracted great research interest. Benefitted from advanced nano-fabrication technologies, 3D or planar chiroptical nanostructures, such as helices, 7,8 shurikens, 9 gammadions, 6,10 and twisted split-rings 11 have been fabricated. On the other hand, extrinsic chirality can also be observed in achiral photonic nanostructures under obliquely incidence conditions. The extrinsic chirality is originated from asymmetric distributions of electromagnetic fields, i.e. the electromagnetic near field distribution is chiral. 12 Nanophotonic structures such as nanoholes, 12 squares 13 and split ring resonators 14,15 showed large extrinsic chirality. For instance, Ben et al.demonstrated a ~4 times stronger optical chirality in achiral periodic nanoholes compared to the gammadion structure. 12 Recently, Abraham et. al. experimentally demonstrated that the achiral nanohole structures can also show superchiral near-fields even at perpendicular incidence conditions. 16 In that case, the far-field circular dichroism (CD) background signals from the plasmonic structures is eliminated, improving the sensitivity for chiral molecule sensing applications. These reports demonstrate a promising potent...

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“…For instance, Ben et aldemonstrated a ~4 times stronger optical chirality in achiral periodic nanoholes compared to the gammadion structure. 12 Recently, Abraham et. al.…”

mentioning

confidence: 99%

Switching the Optical Chirality in Magnetoplasmonic Metasurfaces Using Applied Magnetic Fields

et al. 2020

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“…Typically, it was thought that samples that produced CD had to be chiral, that is, they could not be superimposed with its mirror image 9 . However, recent experiments with planar mirror-symmetric plasmonic structures have shown that a non-zero CD can be obtained if the sample is illuminated at oblique angles [10][11][12][13] . Other attempts to create CD with a non-chiral sample have been carried out surrounding the sample with a chiral medium [14][15][16] .…”

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confidence: 99%

Angular momentum-induced circular dichroism in non-chiral nanostructures

2014

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Circular dichroism, that is, the differential absorption of a system to left and right circularly polarized light, is one of the only techniques capable of providing morphological information of certain samples. In biology, for instance, circular dichroism spectroscopy is widely used to study the structure of proteins. More recently, it has also been used to characterize metamaterials and plasmonic structures. Typically, circular dichorism can only be observed in chiral objects. Here we present experimental results showing that a non-chiral sample such as a subwavelength circular nanoaperture can produce giant circular dichroism when a vortex beam is used to excite it. These measurements can be understood by studying the symmetries of the sample and the total angular momentum that vortex beams carry. Our results show that circular dichroism can provide a wealth of information about the sample when combined with the control of the total angular momentum of the input field.

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“…The research on chiral metasurfaces has covered an astoundingly large portfolio of designs, ranging from the initial famous gammadion shape meta-atom [ 16,28 ] to split-rings, [29][30][31] fi shshapes, [ 32 ] L-shape, [ 33 ] and achiral oriented structures, [34][35][36][37] and spanned the frequencies from visible to gigahertz(GHz). [ 38 ] For the purpose of chiral molecule sensing, [ 39,40 ] it is essential to achieve a pronounced chiral optical response in the UV to near-IR spectral range, where the resonant responses of most chiral molecules lie.…”

Section: A Novel Chiral Metasurface With Controllable Circular Dichromentioning

confidence: 99%

“…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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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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Chiroptical Effects in Planar Achiral Plasmonic Oriented Nanohole Arrays

Cited by 92 publications

References 28 publications

Switching the Optical Chirality in Magnetoplasmonic Metasurfaces Using Applied Magnetic Fields

Switching the Optical Chirality in Magnetoplasmonic Metasurfaces Using Applied Magnetic Fields

Angular momentum-induced circular dichroism in non-chiral nanostructures

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

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