Tapered gold-helix metamaterials as improved circular polarizers

Gansel, Justyna K.; Latzel, Michael; Frölich, Andreas; Kaschke, Johannes; Thiel, Michael; Wegener, Martin

doi:10.1063/1.3693181

Cited by 216 publications

(172 citation statements)

References 10 publications

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“…Using a combination of direct laser writing and electroplating, high-quality structures have been fabricated for mid-infrared frequencies [2]. Both, extinction ratio and bandwidth have been further enhanced by tapering the helix radius along the helix axis [5]. These asymmetric tapered helices show different circular polarization conversions when changing the direction of propagation, making them either good circular polarizers or analyzers, depending on their orientation.…”

Section: Introductionmentioning

confidence: 99%

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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%

“…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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“…Tapered gold-helix metamaterials 21 were designed with direct laser writing to broaden the operation bandwidth in the THz region and reduce polarization intensity conversion 20 . Recently, using the focused ion beam-induced deposition (FIBID) technology, it has been possible to reach a broadband CD in the near-infrared optical region reducing the helix dimension to submicron size 22 .…”

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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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“…[22][23][24] DLW into a positive tone photoresist followed by electroplating with gold is another approach already used to fabricate 3D plasmonic metaatoms. [5,25] Gold helix and tapered-helix mid infrared metamaterials have already been realized utilizing the latter approach. Initially, hollow cavities of the desired architectures are generated within the volume of a positive tone resin by DLW on a conductive substrate and, subsequently, filled with gold using an electrochemical deposition procedure.…”

Section: Introductionmentioning

confidence: 99%

3D Chiral Plasmonic Metamaterials Fabricated by Direct Laser Writing: The Twisted Omega Particle

Sakellari

Yin

Nesterov

et al. 2017

Advanced Optical Materials

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and by exploiting their acute response to their immediate environment, a variety of novel applications have been realized such as negative indices of refraction, [3,4] broadband circular polarization devices, [5] and strongly twisted local electromagnetic fields for sensitive detection of chiral molecules. [6][7][8][9][10] In chiral media, optical activity is a result of the cross-coupling between electric and magnetic fields. Two classical approaches have been proposed to model the mechanisms of optical activity: [11,12] (a) the coupled oscillator model system, where optical activity arises from the coupling of two separate, noncollinear oscillators, and (b) the one-electron model system, where an electron is bound on a helix, giving electric and magnetic character to the optical transitions. Recently, the plasmonic analogue of the coupled oscillator model system, which consists of a system of two cornerstacked gold nanorods, was experimentally demonstrated. [13] This system resembles two coupled, vertically displaced electrons that carry out orthogonal harmonic oscillation driven by an external light field. In this work, we experimentally and theoretically study the plasmonic version of the one-electron model system, which comprises a loop-wire structure, namely the so-called "twisted omega particle." In this case, the 3D plasmonic meta-atom combines a small electric dipole antenna (the metallic wire) and a split-ring resonator (the loop), which exhibits a magnetic dipole resonance leading to a different electromagnetic response to RCP light and the left-handed one (LCP). [14,15] Results and Discussion Fabrication and Optical Characterization Fabrication ApproachTwisted omega architectures have already been theoretically studied and discussed as prototype for plasmonic structures with strong chiro-optical far-field response. [16][17][18][19] To this end, Helgert et al. utilized a layer-by-layer approach to fabricate an architecture reminiscent of the twisted omega by placing two L-shaped gold nanoparticles on top of each other and connected in the vertical direction. [20] Based on a combined spectroscopicThe plasmonic version of a 3D chiral meta-atom which consists of a loopwire structure, namely the so-called twisted omega particle, is experimentally realized. The structure is fabricated by direct laser writing and subsequent electroless silver plating, a novel technique capable of producing truly 3D photonic nanostructures. In this case, the metallic wire of finite length supports an electric dipole resonance, whereas the loop acts as a split-ring resonator which exhibits a magnetic dipole resonance, leading to the separation of right-handed circularly polarized light and the left-handed one. The arising optical activity is discussed in terms of a single oscillator model system used classically to describe the generation of natural optical activity in chiral media, and it is shown that the twisted omega particle acts as its exact plasmonic analogue.

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Tapered gold-helix metamaterials as improved circular polarizers

Cited by 216 publications

References 10 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

Triple-helical nanowires by tomographic rotatory growth for chiral photonics

3D Chiral Plasmonic Metamaterials Fabricated by Direct Laser Writing: The Twisted Omega Particle

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