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Justyna K. Gansel

Bio: Justyna K. Gansel is an academic researcher from Karlsruhe Institute of Technology. The author has contributed to research in topics: Metamaterial & Polarizer. The author has an hindex of 6, co-authored 9 publications receiving 2610 citations.

Papers
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Journal ArticleDOI
18 Sep 2009-Science
TL;DR: This work investigated propagation of light through a uniaxial photonic metamaterial composed of three-dimensional gold helices arranged on a two-dimensional square lattice that is scalable to other frequency ranges and can be used as a compact broadband circular polarizer.
Abstract: We investigated propagation of light through a uniaxial photonic metamaterial composed of three-dimensional gold helices arranged on a two-dimensional square lattice. These nanostructures are fabricated via an approach based on direct laser writing into a positive-tone photoresist followed by electrochemical deposition of gold. For propagation of light along the helix axis, the structure blocks the circular polarization with the same handedness as the helices, whereas it transmits the other, for a frequency range exceeding one octave. The structure is scalable to other frequency ranges and can be used as a compact broadband circular polarizer.

2,252 citations

Journal ArticleDOI
TL;DR: In this paper, the authors show that the bandwidth of a 3D gold helices can be increased to 1.5 octaves by tapering the gold-helix radius.
Abstract: We have previously shown that square arrays of three-dimensional gold helices can serve as compact broadband circular polarizers. Here, we show by heuristic reasoning supported by numerical calculations that the bandwidth of the device can realistically be increased to 1.5 octaves by tapering the gold-helix radius. The tapering also improves the extinction ratio. Depending on the side from which light impinges onto the tapered helices, the polarization conversions are different. Therefore, the structure is either optimal as polarizer or as analyzer. Corresponding structures for the infrared spectral range are fabricated by direct laser writing and gold electroplating.

193 citations

Journal ArticleDOI
TL;DR: This study systematically study the dependence of the metamaterial's chiral optical properties on helix pitch, helix radius, two-dimensional lattice constant, wire radius, number of helix pitches, and angle of incidence.
Abstract: We have recently shown that metamaterials composed of three-dimensional gold helices periodically arranged on a square lattice can be used as compact “thin-film” circular polarizers with one octave bandwidth. The physics of the motif of these artificial crystals is closely related to that of microwave sub-wavelength helical antennas in end-fire geometry. Here, we systematically study the dependence of the metamaterial’s chiral optical properties on helix pitch, helix radius, two-dimensional lattice constant, wire radius, number of helix pitches, and angle of incidence. Our numerical calculations show that the optical properties are governed by resonances of the individual helices, yet modified by interaction effects. Furthermore, our study shows possibilities and limitations regarding performance optimization.

192 citations

Journal ArticleDOI
TL;DR: Symmetry considerations and current progress in the fabrication of N-helix optical metamaterials as broadband circular polarizers is presented, which can be eliminated by recovering four-fold rotational symmetry.
Abstract: Metal-helix based metamaterials have been introduced as compact and broadband circular polarizers. However, the end of the metal wire together with the helix center defines an axis in space, which unavoidably breaks the rotational symmetry at the metamaterial surface. This introduces linear birefringence. Symmetry can be recovered by considering an integer number, e.g. N = 4, of intertwined helices arranged to a square array. We show that the operation principles are fundamentally different though. Metamaterial circular polarizers based on N = 4 helices, unlike single helices, inherently require absorption of the constituent metal. Otherwise, the combination of a four-fold rotational axis and time-inversion symmetry strictly forbids circular-polarizer action. Our symmetry analysis is confirmed by extensive numerical calculations comparing results for perfect electric conductors with those for a free-electron Drude metal with finite damping.

111 citations

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate metamaterial metal-based bolometers, which take advantage of resonant absorption in that a spectral and/or polarization filter can be built into the bolometer.
Abstract: We demonstrate metamaterial metal-based bolometers, which take advantage of resonant absorption in that a spectral and/or polarization filter can be built into the bolometer. Our proof-of-principle gold-nanostructure-based devices operate around 1.5 \mum wavelength and exhibit room-temperature time constants of about 134 \mus. The ultimate detectivity is limited by Johnson noise, enabling room-temperature detection of 1 nW light levels within 1 Hz bandwidth. Graded bolometer arrays might allow for integrated spectrometers with several octaves bandwidth without the need for gratings or prisms and for integrated polarization analysis without external polarization optics.

105 citations


Cited by
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Journal ArticleDOI
TL;DR: This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam.
Abstract: Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components. Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.

4,613 citations

Journal ArticleDOI
22 Jun 2010-ACS Nano
TL;DR: The present review critically investigates to what extent self-assembly can be directed, enhanced, or controlled by either changing the energy or entropy landscapes, using templates or applying external fields.
Abstract: Within the field of nanotechnology, nanoparticles are one of the most prominent and promising candidates for technological applications. Self-assembly of nanoparticles has been identified as an important process where the building blocks spontaneously organize into ordered structures by thermodynamic and other constraints. However, in order to successfully exploit nanoparticle self-assembly in technological applications and to ensure efficient scale-up, a high level of direction and control is required. The present review critically investigates to what extent self-assembly can be directed, enhanced, or controlled by either changing the energy or entropy landscapes, using templates or applying external fields.

1,938 citations

Journal ArticleDOI
15 Mar 2012-Nature
TL;DR: It is shown that DNA origami enables the high-yield production of plasmonic structures that contain nanoparticles arranged in nanometre-scale helices, and it is found that the structures in solution exhibit defined circular dichroism and optical rotatory dispersion effects at visible wavelengths that originate from the collective plAsmon–plasmon interactions of the nanoparticles positioned with an accuracy better than two nanometres.
Abstract: Matter structured on a length scale comparable to or smaller than the wavelength of light can exhibit unusual optical properties. Particularly promising components for such materials are metal nanostructures, where structural alterations provide a straightforward means of tailoring their surface plasmon resonances and hence their interaction with light. But the top-down fabrication of plasmonic materials with controlled optical responses in the visible spectral range remains challenging, because lithographic methods are limited in resolution and in their ability to generate genuinely three-dimensional architectures. Molecular self-assembly provides an alternative bottom-up fabrication route not restricted by these limitations, and DNA- and peptide-directed assembly have proved to be viable methods for the controlled arrangement of metal nanoparticles in complex and also chiral geometries. Here we show that DNA origami enables the high-yield production of plasmonic structures that contain nanoparticles arranged in nanometre-scale helices. We find, in agreement with theoretical predictions, that the structures in solution exhibit defined circular dichroism and optical rotatory dispersion effects at visible wavelengths that originate from the collective plasmon-plasmon interactions of the nanoparticles positioned with an accuracy better than two nanometres. Circular dichroism effects in the visible part of the spectrum have been achieved by exploiting the chiral morphology of organic molecules and the plasmonic properties of nanoparticles, or even without precise control over the spatial configuration of the nanoparticles. In contrast, the optical response of our nanoparticle assemblies is rationally designed and tunable in handedness, colour and intensity-in accordance with our theoretical model.

1,838 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe recent progress in the fabrication of three-dimensional metamaterial structures and discuss some of the remaining challenges, including ultra-high-resolution imaging systems, compact polarization optics and cloaking devices.
Abstract: Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallodielectric subwavelength building blocks. This deceptively simple yet powerful concept allows the realization of many new and unusual optical properties, such as magnetism at optical frequencies, negative refractive index, large positive refractive index, zero reflection through impedance matching, perfect absorption, giant circular dichroism and enhanced nonlinear optical properties. Possible applications of metamaterials include ultrahigh-resolution imaging systems, compact polarization optics and cloaking devices. This Review describes recent progress in the fabrication of three-dimensional metamaterial structures and discusses some of the remaining challenges.

1,594 citations

Journal ArticleDOI
14 Jun 2013-Science
TL;DR: In this paper, the authors demonstrated ultrathin, broadband, and highly efficient metamaterial-based terahertz polarization converters that are capable of rotating a linear polarization state into its orthogonal one.
Abstract: Polarization is one of the basic properties of electromagnetic waves conveying valuable information in signal transmission and sensitive measurements. Conventional methods for advanced polarization control impose demanding requirements on material properties and attain only limited performance. We demonstrated ultrathin, broadband, and highly efficient metamaterial-based terahertz polarization converters that are capable of rotating a linear polarization state into its orthogonal one. On the basis of these results, we created metamaterial structures capable of realizing near-perfect anomalous refraction. Our work opens new opportunities for creating high-performance photonic devices and enables emergent metamaterial functionalities for applications in the technologically difficult terahertz-frequency regime.

1,531 citations