Disposable Plasmonics: Plastic Templated Plasmonic Metamaterials with Tunable Chirality

Karimullah, Affar S.; Jack, Calum; Tullius, Ryan; Rotello, Vincent M.; Cooke, Graeme; Gadegaard, Nikolaj; Barron, Laurence D.; Kadodwala, Malcolm

doi:10.1002/adma.201501816

Cited by 102 publications

(147 citation statements)

References 39 publications

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“…[130] The fabricated template plasmonic substrates (TPSs) can be seen as a solid and inverse structure. The coupling of electric and magnetic fields enabled solid structure overlap with inverse one.…”

Section: Wwwadvopticalmatdementioning

confidence: 99%

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Luo

Chi

Jiang

et al. 2017

Advanced Optical Materials

170

122

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(circular birefringence) and absorption losses (circular dichroism) with the circu larly polarized light (CPL) illumination. [10] CB arises from the difference in the real part of refractive index, leading to a dif ferent velocity for LCP and RCP compo nents, and thus results in the polarization rotation of the linearly polarized incident light. CD corresponds to the difference in the imaginary part of refractive index, resulting in a distinct absorption loss for LCP and RCP excitations. Besides the con ventional CD and CB, asymmetric trans mission (circular conversion dichroism) is another fundamental chiroptical pheno menon, which exists in the nondiffracting array, referring to different LCPtoRCP and RCPtoLCP conversion efficiencies. [11] All of these chiroptical phenomena have been successfully applied in the spectros copy for identifying special arrangements of chiral matters in biology, chemistry and physics as efficient diagnostic tools. [12][13][14][15][16] However, the chirop tical response in natural chiral materials is relatively weak due to the small electromagnetic (EM) interaction volume, [17] hence limits its further applications.Recent progress in plasmonics paves the way for the enhancement of chiroptical response. [18][19][20] Surface plasmons (SPs), as the collective electrons oscillation at the dielectric and metal interface, [21][22][23] present the capacity of light confine ment and field enhancement, which significantly improve the strength of lightmatter interactions. [24][25][26][27][28] With the uptodate nanofabrication technology, the study field of chirality has been extended from traditional chiral molecules to 3D metallic nanostructures. [29][30][31][32] Chiroptical responses of metallic meta molecules have been widely investigated, [33][34][35] and applied in various fields, such as biosensing, [36] chiral catalysis, [37] polari zation tuning, [38] and chiral photo detection.[39] The 3D metallic structure exhibited giant optical activity response because of the strong interaction between electric and magnetic resonant modes. [40,41] Different from 3D chiral ensembles, planar chiral structures show none chiral effect, as they can always coincide with their mirror images. However, 2D chirality was successfully found in the quasitwodimensional (quasi2D) chiral structure. [42] Moreover, recent reports show that even achiral nanomaterials have the ability to generate strong CD under an oblique CPL illumination. [43] This kind of extrinsic chirality arises from sym metry breaking of the incident light and the quasi2D material, which is quite different from the intrinsic chirality of 3D chiral The plasmonic chiroptical effect has been used to manipulate chiral states of light, where the strong field enhancement and light localization in metallic nanostructures can amplify the chiroptical response. Moreover, in metamaterials, the chiroptical effect leads to circular dichroism (CD), circular birefringence (CB), and asymmetric transmission. Potential applications enabled by chiral plasmonics...

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Section: Wwwadvopticalmatdementioning

confidence: 99%

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Luo

Chi

Jiang

et al. 2017

Advanced Optical Materials

170

122

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“…Although planar meta/nanomaterials are thus 3D, it is clear that their threedimensionality is not very pronounced. At optical frequencies, various 3D structured meta/nanomaterials have been proposed, such as rosettes, [24,25] twisted arcs, [26] 3D shuriken, [27] stacked split rings, [28,29] oligomers, [30,31] gyroids, [32] and helices. [33][34][35][36] Of all these examples, the latter (i.e., the helix) is the archetypical chiral structure.…”

Section: Doi: 101002/adma201605110mentioning

confidence: 99%

Strong Rotational Anisotropies Affect Nonlinear Chiral Metamaterials

et al. 2017

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complications as the technique can become too sensitive, making it difficult to separate the desirable and undesirable contributions to the SHG signal. An example of an undesirable complication is extrinsic chirality, [15,16] which affects the nonlinear susceptibility tensor components in SHG. [17,18] Any anisotropy present in the sample can have a similar effect and our work here focuses on highlighting the effects of rotational anisotropy. We begin by selecting the sample geometry.Chirality is intrinsically a 3D property; however, a great number of works have focused on so-called "planar" nanostructures. A few recent examples include S-shaped nanostructures, [19,20] three-and fourfold symmetric propellers, [21] and heptamers. [22] These planar chiral nanostructures are very attractive because of their ease of fabrication with electron beam lithography. The necessary 3D symmetry-breaking arises from a dissymmetry along the axis perpendicular to the sample plane, [23] for instance, due to the presence of a substrate on one side of the sample and air on the other. Although planar meta/nanomaterials are thus 3D, it is clear that their threedimensionality is not very pronounced. At optical frequencies, various 3D structured meta/nanomaterials have been proposed, such as rosettes, [24,25] twisted arcs, [26] 3D shuriken, [27] stacked split rings, [28,29] oligomers, [30,31] gyroids, [32] and helices. [33][34][35][36] Of all these examples, the latter (i.e., the helix) is the archetypical chiral structure. The strong interaction of nanohelices with circularly polarized light (CPL) gives rise to large chiroptical effects, such as circular dichroism. This makes them attractive for applications involving CPL. [6,8,[37][38][39] Thus, the nonlinear optical response of helical metamaterials is of particular interest as they already demonstrate strong linear chiroptical effects. However, until recently it has been very difficult to fabricate high quality helical metamaterials for use at optical frequencies. Herein, we have investigated a chiral metamaterial made of nanohelices, with substantially subwavelength dimensions (<λ/10). As the archetypical chiral geometry, the helical design is particularly suitable because it is pronouncedly 3D, it gives rise directly to superchiral field configurations along the center of the helix, and its structural chirality parameter is straightforward to estimate as a function of varying dimensions. [33,40] Within this metamaterial, we clearly identify three different rotational anisotropies and demonstrate how they can mask the true chiral effect, rendering the SHG-CD signals unreliable. Our experimental results highlight the need for a general method to extract the true chiral contributions to the SHG signal. Here, we use a method for approximating these contributions. Although not fully rigorous, this method yields three measures of the chirality: averaged SHG-CD, direct inspection of the chiral component of the effective susceptibility tensor, and evaluation of the chiral coefficients tha...

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“…The building blocks for solid‐state chiral metamaterials on substrates are either inherently chiral plasmonic nanostructures or anisotropic achiral plasmonic nanostructures stacked into chiral structures with site‐specific twists . Fabrication of these building blocks often requires sophisticated lithographic techniques such as e‐beam lithography and focused ion‐beam lithography to define features at the nanoscale for targeted performances.…”

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confidence: 99%

Moiré Chiral Metamaterials

Zheng

2017

Advanced Optical Materials

107

117

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nanostructures as building blocks. The excitation of the light-coupled collective resonances of free electrons in plasmonic nanostructures leads to the strong lightmatter interactions at the subwavelength scale. The chiral configuration makes the interactions depend on whether the incident light has left-handed circularly polarization (LCP) or right-handed circularly polarization (RCP). Therefore, it is possible to achieve plasmonic chiral metamaterials with strongly enhanced chiroptical effects and compact size. [1,[16][17][18] A large number of plasmonic chiral metamaterials with different configurations have been demonstrated including gammadions, [19] helixes, [10] and self-assembled chiral super structures. [20] The building blocks for solid-state chiral metamaterials on substrates are either inherently chiral plasmonic nanostructures [21][22][23][24] or anisotropic achiral plasmonic nanostructures stacked into chiral structures with site-specific twists. [25][26][27][28] Fabrication of these building blocks often requires sophisticated lithographic techniques such as e-beam lithography and focused ion-beam lithography to define features at the nanoscale for targeted performances. Moreover, multistep precise alignments are needed to fabricate the metamaterials consisted of the stacked building blocks. The structural and spatial precision for the building blocks is often below 50 nm for the metamaterials working in the visible and near-infrared regimes, limiting the fabrication throughput, scalability, and reproducibility. In addition, new design and fabrication of the samples are needed to tune the chiroptical responses.Herein, we report a new type of chiral metamaterials, known as moiré chiral metamaterials (MCMs), consisted of two layers of identical achiral Au nanohole arrays stacked into moiré patterns. In contrast to the previously reported plasmonic chiral metamaterials based on local structural chirality or site-specific twisting of anisotropic components, the optical chirality of MCMs is originated from relative in-plane rotation between the lattice directions of the two identical achiral layers. The chiroptical responses of the moiré chiral metamaterials can be precisely tuned by the in-plane rotation between the two layers of nanohole arrays. Through experimental and theoretical studies, we reveal mechanism behind the chiroptical effects in the moiré chiral metamaterials. Furthermore, we apply the moiré chiral metamaterials to achieve label-free enantiodiscrimination of biomolecules and drug molecules at the picogram level. With their ultrathin thickness (≈70 nm, which is only ≈1/10 of the operation wavelength), strong chirality, and high tunability, Plasmonic chiral metamaterials are promising for applications in chiral sensors and photonic devices due to their strong optical chirality and lightmatter interactions at the subwavelength scale. However, most of current plasmonic chiral metamaterials rely on local structural chirality or site-specific symmetry breaking, which has limited their optica...

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Disposable Plasmonics: Plastic Templated Plasmonic Metamaterials with Tunable Chirality

Cited by 102 publications

References 39 publications

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Strong Rotational Anisotropies Affect Nonlinear Chiral Metamaterials

Moiré Chiral Metamaterials

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