Giant Nonlinear Optical Activity of Achiral Origin in Planar Metasurfaces with Quadratic and Cubic Nonlinearities

Chen, Shumei; Zeuner, Franziska; Weismann, Martin; Reineke, Bernhard; Li, Guixin; Valev, Ventsislav K.; Cheah, Kok Wai; Panoiu, Nicolae C.; Zentgraf, Thomas; Zhang, Shuang

doi:10.1002/adma.201505640

Cited by 99 publications

(89 citation statements)

References 39 publications

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“…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.…”

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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Section: Doi: 101002/adma201605110mentioning

confidence: 99%

Strong Rotational Anisotropies Affect Nonlinear Chiral Metamaterials

et al. 2017

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“…From the viewpoint of classical electrodynamics, the degeneracy between the helicity eigenmodes of light, i.e., left and right circularly polarized (LCP and RCP) waves, is broken due to cross coupling between the electric and magnetic dipoles in a chiral medium, leading to differential extinction (CD) or transmission (optical activity) for LCP/ RCP waves. Compared with naturally occurring materials, they often have significantly enhanced chirality and thus enable many fascinating phenomena such as pronounced linear [4][5][6][7] and nonlinear chiroptical effects, [8,9] negative refraction, [10][11][12] manipulating Casimir effect, [13][14][15] unusual spin Hall effect of light, [16] and chiral-selective nonlinear imaging. However, these effects induced by magnetoelectric coupling in natural materials, particularly in biomolecules like amino acids, sugars, proteins, and viruses, are often very weak.…”

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confidence: 99%

Ultrabroadband Optical Superchirality in a 3D Stacked‐Patch Plasmonic Metamaterial Designed by Two‐Step Glancing Angle Deposition

Hou

Leung

Chan

et al. 2016

Adv Funct Materials

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7807wileyonlinelibrary.com respectively from the interaction of circularly or linearly polarized light with structurally chiral media in nature, such as chiral (bio)molecules and solids without any mirror symmetry. From the viewpoint of classical electrodynamics, the degeneracy between the helicity eigenmodes of light, i.e., left and right circularly polarized (LCP and RCP) waves, is broken due to cross coupling between the electric and magnetic dipoles in a chiral medium, leading to differential extinction (CD) or transmission (optical activity) for LCP/ RCP waves. These chiroptical effects provide an effective approach for manipulating polarization states of light in various optical and photonic applications, and also for sensing enantiomers of chemical molecules and determining structural conformation of biological molecules. However, these effects induced by magnetoelectric coupling in natural materials, particularly in biomolecules like amino acids, sugars, proteins, and viruses, are often very weak. [1] This unfavorable feature not only limits the ability of naturally occurring materials to effectively manipulate light polarization at the nanoscale, particularly for nanophotonics applications, but also severely restricts the application of chirality-sensitive spectroscopic techniques to samples at the microgram level. [1][2][3] Recently, plasmonic chiral metamaterials (PCMs) made of subwavelength metal nanostructures, artificially engineered chiral resonators that cannot be superimposed on their mirror images, have attracted a considerable amount of research interest. Compared with naturally occurring materials, they often have significantly enhanced chirality and thus enable many fascinating phenomena such as pronounced linear [4][5][6][7] and nonlinear chiroptical effects, [8,9] negative refraction, [10][11][12] manipulating Casimir effect, [13][14][15] unusual spin Hall effect of light, [16] and chiral-selective nonlinear imaging. [17,18] Depending on their spatial dimensions, the PCMs developed thus far can be either 2D (or planar) or 3D. The planar 2D PCMs are composed of periodic arrays of plasmonic resonators such as gold gammadions, [5,7] fish-scale, [19][20][21] and G-shape nanostructures, [22] and their chiroptical effects are generally asymmetric with respect Low-cost and large-scale fabrication of 3D chiral metamaterials is highly desired for potential applications such as nanophotonics devices and chiral biosensors. One of the promising fabrication methods is to use glancing angle deposition (GLAD) of metal on self-assembled dielectric microsphere array. However, structural handedness varies locally due to long-range disorder of the array and therefore large-scale realization of the same handedness is impossible. Here, using symmetry considerations a two-step GLAD process is proposed to eliminate this longstanding problem. In the proposed scheme, the unavoidable long-range disorder gives rise to microscale domains of the same handedness but of slightly different structural geometries and ultima...

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“…16 The interplay of nonlinearity and circular dichroism (CD) was highlighted from the observation of strong cross-phase modulation and four-wave mixing in a type of varactor-loaded nonlinear chiral metamaterial. 17 Chirality signatures of individual twisted-cross gold nanodimers via SHG microscopy, 18 nonlinear imaging and spectroscopy of artificial enantiomers of a twisted-arc metamaterial, 19 and harmonic generation of optical activity 22 Furthermore, we also demonstrate that rotating the gammadion around its rotational axis can continuously control the phase of the THG, and thus can be utilized in the FZP design to rotate the polarization of the output THG signals. Fig.…”

confidence: 70%

“…15 Recently, there is also a growing interest in nonlinear optical signals generated from chiral plasmonic nanostructures, which provide a promising platform to study chiral-selective nonlinear optical interactions. [16][17][18][19][20][21][22] For example, asymmetric SHG from chiral G-shaped gold nanostructures upon a reverse of the handedness of the structures was presented. 16 The interplay of nonlinearity and circular dichroism (CD) was highlighted from the observation of strong cross-phase modulation and four-wave mixing in a type of varactor-loaded nonlinear chiral metamaterial.…”

confidence: 99%

Controlling third harmonic generation with gammadion-shaped chiral metamaterials

Zhang

Yang

et al. 2016

AIP Advances

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We theoretically investigated third harmonic generation (THG) from planar chiral metamaterials consisting of a square array of gammadion-shaped metal-insulator-metal multilayered nanostructures. We show that there exists strong circular dichroism (CD) for THG on the proposed chiral metamaterials. We also demonstrate that geometrically mirroring the gammadion -shaped meta-atoms can result in reversal of the THG-CD effect. Based on these CD effects in the optical nonlinear regime, we propose a design of a Fresnel zone plate (FZP) for intense focusing of the THG signals, in which adjacent zones of the FZP consist of gammadions with mirror symmetry and generate circularly polarized THG with opposite handedness. Furthermore, we demonstrate that the relative phase of the THG can be continuously changed by rotating the gammadion around its rotational axis, which could be used in the FZP to control the polarization of the output THG signals.

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Giant Nonlinear Optical Activity of Achiral Origin in Planar Metasurfaces with Quadratic and Cubic Nonlinearities

Cited by 99 publications

References 39 publications

Strong Rotational Anisotropies Affect Nonlinear Chiral Metamaterials

Strong Rotational Anisotropies Affect Nonlinear Chiral Metamaterials

Ultrabroadband Optical Superchirality in a 3D Stacked‐Patch Plasmonic Metamaterial Designed by Two‐Step Glancing Angle Deposition

Controlling third harmonic generation with gammadion-shaped chiral metamaterials

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