Epsilon-Near-Zero Materials

Conformable optical coatings with epsilon near zero response

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In this paper, published in APL Photonics, we design and experimentally demonstrate an optical free-standing and low-loss epsilon-near-zero (ENZ) metamaterial which shows a vanishing effective permittivity at the visible range. We fabricate the flexible ENZ membrane using the sacrificial layer-assisted method by stacking polymer (SU-8) and silver nano-layers. The obtained membranes do not show any sign of degradation even after several thousand bending cycles (BCs). Additionally, we demonstrate that our ENZ material can conform to targets with a radius of curvature of a few microns. This material permits to coat any substrate or device with a tailored made “photonic skin”, decoupling the fabrication requirements from… Read More »Conformable optical coatings with epsilon near zero response

Optically Induced Metal-to-Dielectric Transition in Epsilon-Near-Zero Metamaterials

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Our work on the “Optically Induced Metal-to-Dielectric Transition in Epsilon-Near-Zero Metamaterials” has recently appeared in Scientific Reports. In this work we designed a metamaterial with epsilon-near-zero (ENZ) response, that is tuned all-optically from a metallic to dielectric behaviour. The transition is demonstrated using an ultrafast pump and probe scheme. The study unveils both analytically and experimentally the full associated nonlinear dynamics. The full article can be found here.

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