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Plasmonics and Metamaterials

Enhanced Nonlinear Refractive Index in Epsilon-Near-Zero Materials

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In collaboration with Heriot-Watt University and Purdue University, we published a paper in Phys. Rev. Lett. demonstrating that epsilon-near-zero metamaterials (ENZ) exhibit an enhanced nonlinear response. In this study we demonstrated a six-fold enhancement of the Kerr nonlinear refractive index in proximity of the ENZ condition, in the near-infrared. The experiemtn was performed on Al-doped ZnO (AZO) thin film, and demonstrates a general behaviour of ENZ materials. The full paper can be found here.

Chiral Epsilon-Near-Zero Metamaterials

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In a paper published in Physical Review Letters we demonstrate that a one-dimensional stack of achiral material can exhibit electromagnetic chirality… Artificial chirality is currently a very much-researched field both from a fundamental point of view and for its applications in molecular biology, life science, optics, crystallography and particle physics. In this context, plasmonic-based metamaterials are the natural platform of choice because their smallest constituents (meta-atoms) can be engineered to exhibit artificial chirality. This is usually achieved by breaking the spatial symmetry of the meta-atoms, structuring plasmonic materials at the nanoscale, either in 3D (akin to natural chirality) or in 2D, but never in 1D. Here… Read More »Chiral Epsilon-Near-Zero Metamaterials

Optical guided mode resonance filter on a flexible substrate

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In Optical guided mode resonance filter on a flexible substrate, published in Optics Express, we present the design, fabrication and characterization of a new filtering platform, based on the principle of Guided Mode Resonance. The filters consist of plasmonic nanofeatures realised on flexible polymer substrates, and work down to the visible range. In this paper we also exhibit an example proof-of-concept application by mounting the sample directly onto the end of a collimated fibre output, as shown in the figure.  This progresses research on lab-on-fibre technologies, introducing an alternative to directly fabricating structures on the end of a fibre, and rather produce fibre terminating caps which can be… Read More »Optical guided mode resonance filter on a flexible substrate

Nanoplasmonic Filters for Hollow Core Photonic Crystal Fibres

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Photonic crystal fibres are an essential tool in many experiments which require their sensing or highly non-linear properties.  Using our ability to fabricate flexible plasmonic structures, we have been able to functionalise the facet of a hollow core photonic crystal fibre with a spectral filter. This brings the possibility to combine Lab-on-Fibre (LoF) technologies with photonic crystal fibres, expanding the available toolkit of LoF functions. Using a flexible plasmonic membrane allows the fibre to be given a function reversibly, and without having to directly write onto the fibre’s facet itself.  Crucially this allows us to realise LoF on a hollow core photonic crystal fibre, which… Read More »Nanoplasmonic Filters for Hollow Core Photonic Crystal Fibres

Reproducible SERS Substrate

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In a recently published article in ACS Nano, we demonstrate a SERS substrate capable of reproducible measurements, such that the relative concentration of a mixture of SERS active molecules can be determined. Surface enhanced Raman spectroscopy has become a widely used research tool for the identification of molecules, but has yet to achieve widespread use outside of academia.  The dominant method for generating the required spectra is to use colloidal metallic nanoparticles, but this leads to an inherently random distribution of SERS-active sites, and thus although the signal can uniquely identify a molecule, the intensity of that signal will vary, rendering quantitative analysis impossible. We use… Read More »Reproducible SERS Substrate

Coherent control of plasmonic nanoantennas using optical eigenmodes

In a paper published in Nature Scientific Report we show how to couple light to subwavelenght plasmonic features using the principle of optical eigenmodes. This technique can be used also in presence of large optical aberrations and allow to selectively couple light to nanofeatures in a crowded region, with minimal crosstalk. In the picture we show a SEM picture of a typical sample (gold nanoantennas on glass) that we fabricated to test the technique.

Flexible Metamaterials

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Metamaterials (MMs) are man made materials with unusual electromagnetic properties that are not typically found in Nature. They are the key to achieving such extraordinary properties as invisibility cloaks and perfect lenses. At present, they are bulky and confined to laboratories. If they were flexible, they could become much more versatile and practical. We are working towards a novel concept for flexible MMs (Metaflex) that will turn current cloaking devices from suits of armour into true cloaks.   In the following figure a single layer of Metaflex is placed on a commercial disposable contact lens, to show the potential of the approach. Our interest in Metaflex… Read More »Flexible Metamaterials