Wafer scale fabrication of porous three-dimensional plasmonic metamaterials for the visible region: chiral and beyond

Singh, Haobijam Johnson; Nair, Greshma; Ghosh, Arijit; Ghosh, Ambarish

doi:10.1039/c3nr02666c

Cited by 89 publications

(108 citation statements)

References 33 publications

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“…The Ghosh group in 2013 circumvented this problem by first creating a dielectric helical template via GLAD, which was subsequently covered with gold or silver nanoparticles by physical vapor deposition under a small tilt angle [49]. The process is illustrated in Figure 7(a).…”

Section: Glancing-angle Depositionmentioning

confidence: 99%

Optical and Infrared Helical Metamaterials

Kaschke

Wegener

2016

Nanophotonics

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By tailoring metamaterials with chiral unit cells, giant optical activity and strong circular dichroism have been achieved successfully over the past decade. Metamaterials based on arrays of metal helices have revolutionized the field of chiral metamaterials, because of their capability of exhibiting these pronounced chiro-optical effects over previously unmatched bandwidths. More recently, a large number of new metamaterial designs based on metal helices have been introduced with either optimized optical performance or other chiro-optical properties for novel applications. The fabrication of helical metamaterials is, however, challenging and even more so with growing complexity of the metamaterial designs. As conventional two-dimensional nanofabrication methods, for example, electron-beam lithography, are not well suited for helical metamaterials, the development of novel three-dimensional fabrication approaches has been triggered. Here, we will discuss the theory for helical metamaterials and the principle of operation. We also review advancements in helical metamaterial design and their limitations and influence on optical performance. Furthermore, we will compare novel nano-and microfabrication techniques that have successfully yielded metallic helical metamaterials. Finally, we also discuss recently presented applications of helical metamaterials extending beyond the use of far-field circular polarizers.

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Section: Glancing-angle Depositionmentioning

confidence: 99%

Optical and Infrared Helical Metamaterials

Kaschke

Wegener

2016

Nanophotonics

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“…The small size of the NPs is of utmost importance in engineering the chiro-optical response in the visible part of the spectrum. Using our techniques, we were successful [22] in fabricating 3D plasmonic nanostructures with highest chiro-optical response values reported so far in the literature.…”

Section: Introductionmentioning

confidence: 66%

Metallic nanoparticles arranged in a Helical geometry: route towards strong and broadband chiro-optical response

et al. 2014

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Recent advances in nanotechnology have paved ways to various techniques for designing and fabricating novel nanostructures incorporating noble metal nanoparticles, for a wide range of applications. The interaction of light with metal nanoparticles (NPs) can generate strongly localized electromagnetic fields (Localized Surface Plasmon Resonance, LSPR) at certain wavelengths of the incident beam. In assemblies or structures where the nanoparticles are placed in close proximity, the plasmons of individual metallic NPs can be strongly coupled to each other via Coulomb interactions. By arranging the metallic NPs in a chiral (e.g. helical) geometry, it is possible to induce collective excitations, which lead to differential optical response of the structures to right-and left circularly polarized light (e.g. Circular Dichroism -CD). Earlier reports in this field include novel techniques of synthesizing metallic nanoparticles on biological helical templates made from DNA, proteins etc. In the present work, we have developed new ways of fabricating chiral complexes made of metallic NPs, which demonstrate a very strong chiro-optical response in the visible region of the electromagnetic spectrum. Using DDA (Discrete Dipole Approximation) simulations, we theoretically studied the conditions responsible for large and broadband chiro-optical response. This system may be used for various applications, for example those related to polarization control of visible light, sensing of proteins and other chiral bio-molecules, and many more.

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“…37 Although initially nonspherical, the NPs can become spherical upon heating. 38,39 Upon continuation of the heating step, as shown in the SEM images shown in Figure 3A, the separation between the NPs can be controlled reasonably well, without significant variation in the particle size.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Plasmonic Interactions at Close Proximity in Chiral Geometries: Route toward Broadband Chiroptical Response and Giant Enantiomeric Sensitivity

et al. 2014

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Chiral metamaterials can have diverse technological applications, such as engineering strongly twisted local electromagnetic fields for sensitive detection of chiral molecules, negative indices of refraction, broadband circular polarization devices, and many more. These are commonly achieved by arranging a group of noble-metal nanoparticles in a chiral geometry, which, for example, can be a helix, whose chiroptical response originates in the dynamic electromagnetic interactions between the localized plasmon modes of the individual nanoparticles. A key question relevant to the chiroptical response of such materials is the role of plasmon interactions as the constituent particles are brought closer, which is investigated in this paper through theoretical and experimental studies. The results of our theoretical analysis, when the particles are brought in close proximity are dramatic, showing a large red shift and enhancement of the spectral width and a near-exponential rise in the strength of the chiroptical response. These predictions were further confirmed with experimental studies of gold and silver nanoparticles arranged on a helical template, where the role of particle separation could be investigated in a systematic manner. The "optical chirality" of the electromagnetic fields in the vicinity of the nanoparticles was estimated to be orders of magnitude larger than what could be achieved in all other nanoplasmonic geometries considered so far, implying the suitability of the experimental system for sensitive detection of chiral molecules. ■ INTRODUCTIONStrong light matter interactions in metallic nanoparticles (NPs), especially those made of noble metals such as gold and silver, is at the heart of much ongoing research in nanophotonics. Individual NPs can support collective excitations (plasmons) of the electron plasma at certain wavelengths, known as the localized surface plasmon resonance (LSPR), 1 which forms the basis of bright colors in colloidal solutions of Au and Ag and provides a powerful platform for various sensing, imaging, and therapeutic technologies. 2,3 It is interesting to note that the optical properties of a collection of NPs can be significantly different from isolated particles, an effect that originates in the electromagnetic interactions between the localized plasmon modes. This problem has been considered in one and two dimensions with periodic, 4−7 as well as with random, 8−10 arrays of NPs, and it was found that as the particles are brought closer, the plasmon resonances show distinct broadening, along with significant red or blue shifts in their spectral positions, where the sign of the shift depends on the direction of polarization with respect to the interparticle axes. With recent advances in nanotechnology, it has now been possible to develop wafer scale methods of fabricating 3-D arrays of NPs, 11,12 whose sizes and spacing could be engineered with high precision. Of great current interest is that of a chiral arrangement of NPs 13−16 that has been shown to give rise to strong chi...

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Wafer scale fabrication of porous three-dimensional plasmonic metamaterials for the visible region: chiral and beyond

Cited by 89 publications

References 33 publications

Optical and Infrared Helical Metamaterials

Optical and Infrared Helical Metamaterials

Metallic nanoparticles arranged in a Helical geometry: route towards strong and broadband chiro-optical response

Plasmonic Interactions at Close Proximity in Chiral Geometries: Route toward Broadband Chiroptical Response and Giant Enantiomeric Sensitivity

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