Hyperbolic metamaterials for terahertz applications

We develop a method for fabricating hyperbolic metamaterials for terahertz (THz) applications. We prepare a porous silicon matrix with a triangular lattice of holes, which we fill with copper by means of electrochemical deposition. We study transmission properties of this wire medium using THz time-domain spectroscopy, and demonstrate hyperbolic media properties

Wire metamaterials: physics and applications

The physics and applications of a broad class of artificial electromagnetic materials composed of lattices of aligned metal rods embedded in a dielectric matrix are reviewed. Such structures are here termed wire metamaterials. They appear in various settings and can operate from microwaves to THz and optical frequencies. An important group of these metamaterials is a wire medium possessing extreme optical anisotropy. The study of wire metamaterials has a long history, however, most of their important and useful properties have been revealed and understood only recently, especially in the THz and optical frequency ranges where the wire media correspond to the lattices of microwires and nanowires, respectively. Another group of wire metamaterials are arrays and lattices of nanorods of noble metals whose unusual properties are driven by plasmonic resonances. Wire metamaterials appear in various settings, and they can operate in a wide range of frequencies. Such materials are known to possesses extreme optical anisotropy, and their important properties have been revealed and understood only recently, especially in the optical frequency ranges where the wire media correspond to the lattices of nanowires or nanorods. Examples shown include wire media employed for subwavelength imaging, and also an array of free-standing nanorods

www.advmat.de www.MaterialsViews.com Wire Metamaterials: Physics and Applications

The physics and applications of a broad class of artificial electromagnetic materials composed of lattices of aligned metal rods embedded in a dielectric matrix are reviewed. Such structures are here termed wire metamaterials. They appear in various settings and can operate from microwaves to THz and optical frequencies. An important group of these metamaterials is a wire medium possessing extreme optical anisotropy. The study of wire metamaterials has a long history, however, most of their important and useful properties have been revealed and understood only recently, especially in the THz and optical frequency ranges where the wire media correspond to the lattices of microwires and nanowires, respectively. Another group of wire metamaterials are arrays and lattices of nanorods of noble metals whose unusual properties are driven by plasmonic resonances. 1

Manipulating polarization of light with ultrathin epsilon-near-zero metamaterials

One of the basic functionalities of photonic devices is the ability to manipulate the polarization state of light. Polarization components are usually implemented using the retardation effect in natural birefringent crystals and, thus, have a bulky design. Here, we have demonstrated the polarization manipulation of light by employing a thin subwavelength slab of metamaterial with an extremely anisotropic effective permittivity tensor. Polarization properties of light incident on the metamaterial in the regime of hyperbolic, epsilon-near-zero, and conventional elliptic dispersions were compared. We have shown that both reflection from and transmission through λ/20 thick slab of the metamaterial may provide nearly complete linear-to-circular polarization conversion or 90° linear polarization rotation, not achievable with natural materials. Using ellipsometric measurements, we experimentally studied the polarization conversion properties of the metamaterial slab made of the plasmonic nanorod arrays in different dispersion regimes. We have also suggested all-optical ultrafast control of reflected or transmitted light polarization by employing metal nonlinearities.This work has been supported in part by EPSRC (UK) and ERC. P. G. acknowledges support from the Royal Society via the Newton International Fellowship

Manipulating polarization of light with ultrathin epsilon-near-zero metamaterials

[EN] One of the basic functionalities of photonic devices is the ability to manipulate the polarization state of light. Polarization components are usually implemented using the retardation effect in natural birefringent crystals and, thus, have a bulky design. Here, we have demonstrated the polarization manipulation of light by employing a thin subwavelength slab of metamaterial with an extremely anisotropic effective permittivity tensor. Polarization properties of light incident on the metamaterial in the regime of hyperbolic, epsilon-near-zero, and conventional elliptic dispersions were compared. We have shown that both reflection from and transmission through./20 thick slab of the metamaterial may provide nearly complete linear-to-circular polarization conversion or 90 linear polarization rotation, not achievable with natural materials. Using ellipsometric measurements, we experimentally studied the polarization conversion properties of the metamaterial slab made of the plasmonic nanorod arrays in different dispersion regimes. We have also suggested all-optical ultrafast control of reflected or transmitted light polarization by employing metal nonlinearities. (C) 2013 Optical Society of AmericaThis work has been supported in part by EPSRC (UK) and ERC. P. G. acknowledges support from the Royal Society via the Newton International Fellowship.Ginzburg, P.; Rodríguez Fortuño, FJ.; Wurtz, G.; Dickson, W.; Murphy, A.; Morgan, F.; Pollard, R.... (2013). Manipulating polarization of light with ultrathin epsilon-near-zero metamaterials. Optics Express. 21(12):14907-14917. doi:10.1364/OE.21.014907S14907149172112Papakostas, A., Potts, A., Bagnall, D. M., Prosvirnin, S. L., Coles, H. J., & Zheludev, N. I. (2003). Optical Manifestations of Planar Chirality. 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Metal-free quantum-based metamaterial for surface plasmon polariton guiding with amplification. Journal of Applied Physics, 104(6), 063513. doi:10.1063/1.2978208Cortes, C. L., Newman, W., Molesky, S., & Jacob, Z. (2012). Quantum nanophotonics using hyperbolic metamaterials. Journal of Optics, 14(6), 063001. doi:10.1088/2040-8978/14/6/063001Poddubny, A. N., Belov, P. A., Ginzburg, P., Zayats, A. V., & Kivshar, Y. S. (2012). Microscopic model of Purcell enhancement in hyperbolic metamaterials. Physical Review B, 86(3). doi:10.1103/physrevb.86.035148Ziolkowski, R. W. (2004). Propagation in and scattering from a matched metamaterial having a zero index of refraction. Physical Review E, 70(4). doi:10.1103/physreve.70.046608Silveirinha, M., & Engheta, N. (2006). Tunneling of Electromagnetic Energy through Subwavelength Channels and Bends usingε-Near-Zero Materials. Physical Review Letters, 97(15). doi:10.1103/physrevlett.97.157403Edwards, B., Alù, A., Young, M. 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Chemical origins of a fast-charge performance in disordered carbon anodes

Fast charging of lithium-ion cells often causes capacity loss and limited cycle life, hindering their use in high-power applications. Our study employs electrochemical analysis and a multiphysics model to identify and quantify chemical and physical constraints during fast charging, comparing state-of-the-art graphite and nanocluster carbon (nC, a disordered carbon) anodes. The combination of modeling material phase separation phenomena with ion-electron transfer theory reveals significant insight. The active material strongly influences charge transfer kinetics and solid-state lithium diffusion. Unlike graphite, nC supports lithium insertion without phase separation, enabling faster lithium diffusion, better volume utilization, and lower charge transfer resistance. We demonstrate practical implications of these material phenomena through multilayer pouch cells made with nC anodes, which withstand over 5000 fast-charge cycles at 2C without significant degradation (<10% at reference 0.2C)