Giant Chiral Optical Response from a Twisted-Arc Metamaterial

Cui, Yonghao; Kang, Lei; Lan, Shoufeng; Rodrigues, Sean P.; Cai, Wenshan

doi:10.1021/nl404572u

Cited by 283 publications

(217 citation statements)

References 30 publications

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“…In contrast, in metamaterials, they can be many orders of magnitude larger [1][2][3][4][5][6][7][8] and can also be tuned to desired operation wavelengths. The status has been reviewed in [9].…”

Section: Introductionmentioning

confidence: 99%

Tapered N-helical metamaterials with three-fold rotational symmetry as improved circular polarizers

Kaschke¹,

Blome²,

Burger³

et al. 2014

Opt. Express

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Abstract:Chiral helix-based metamaterials can potentially serve as compact and broadband circular polarizers. We have recently shown that the physics of structures composed of multiple intertwined helices, so called N-helices with N being an integer multiple of 4, is distinct from that of structures made of single circular helices (N = 1). In particular, undesired circular polarization conversion is strictly eliminated for N = 4 helices arranged on a square lattice. However, the fabrication of such structures for infrared/visible operation wavelengths still poses very significant challenges. Thus, we here revisit the possibility of reducing N from 4 to 3, which would ease micro-fabrication considerably. We show analytically that N = 3 helices arranged on a hexagonal lattice exhibit strictly vanishing circular polarization conversion. N = 3 is the smallest option as N = 2 obviously leads to linear birefringence. To additionally improve the circular-polarizer operation bandwidth and the extinction ratio while maintaining high transmission for the wanted polarization and zero conversion, we also investigate by numerical calculations N = 3 helices with tapered diameter along the helix axis. We find operation bandwidths as large as 2.4 octaves.

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Section: Introductionmentioning

confidence: 99%

Tapered N-helical metamaterials with three-fold rotational symmetry as improved circular polarizers

Kaschke¹,

Blome²,

Burger³

et al. 2014

Opt. Express

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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.…”

mentioning

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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“…However, these structures need oblique incidence of light to discriminate polarizations with opposite handedness and also exhibit weak dichroic selection. To maximize the interaction with light, chiral metamaterials should extrude along the third dimension, that is, by a stacked arrangement of a unit cell (quasi-three-dimensional (3D) objects) [10][11][12][13][14][15] . In particular, fully 3D helix-based metamaterials can be considered as the best candidates for pronounced chiral response integrated in compact devices, as demonstrated by the fully 3D helical metamaterials acting as circular polarizers in the infrared range 2 , and realized by direct laser writing.…”

mentioning

confidence: 99%

Triple-helical nanowires by tomographic rotatory growth for chiral photonics

et al. 2015

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Three dimensional helical chiral metamaterials resulted in effective manipulation of circularly polarized light in the visible infrared for advanced nanophotonics. Their potentialities are severely limited by the lack of full rotational symmetry preventing broadband operation, high signal-to-noise ratio and inducing high optical activity sensitivity to structure orientation. Complex intertwined three dimensional structures such as multiple-helical nanowires could overcome these limitations, allowing the achievement of several chiro-optical effects combining chirality and isotropy. Here we report three dimensional triple-helical nanowires, engineered by the innovative tomographic rotatory growth, on the basis of focused ion beam-induced deposition. These three dimensional nanostructures show up to 37% of circular dichroism in a broad range (500-1,000 nm), with a high signal-to-noise ratio (up to 24 dB). Optical activity of up to 8°only due to the circular birefringence is also shown, tracing the way towards chiral photonic devices that can be integrated in optical nanocircuits to modulate the visible light polarization.

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Giant Chiral Optical Response from a Twisted-Arc Metamaterial

Cited by 283 publications

References 30 publications

Tapered N-helical metamaterials with three-fold rotational symmetry as improved circular polarizers

Tapered N-helical metamaterials with three-fold rotational symmetry as improved circular polarizers

Strong Rotational Anisotropies Affect Nonlinear Chiral Metamaterials

Triple-helical nanowires by tomographic rotatory growth for chiral photonics

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