Recent experiments have shown the viability of the metamaterial approach to dielectric response engineering for enhancing the transition temperature, Tc, of a superconductor. In this report, we demonstrate the use of Al2O3-coated aluminium nanoparticles to form the recently proposed epsilon near zero (ENZ) core-shell metamaterial superconductor with a Tc that is three times that of pure aluminium. IR reflectivity measurements confirm the predicted metamaterial modification of the dielectric function thus demonstrating the efficacy of the ENZ metamaterial approach to Tc engineering. The developed technology enables efficient nanofabrication of bulk aluminium-based metamaterial superconductors. These results open up numerous new possibilities of considerable Tc increase in other simple superconductors.

We demonstrate a novel artificial optical material, the ''photonic hyper-crystal'', which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. Over the last few decades a considerable progress has been made in developing artificial optical materials with novel and often counterintuitive properties. Revolutionary research by Yablonovitch and John on photonic crystals 1,2 was followed by the development of electromagnetic metamaterial paradigm by Pendry 3 . Even though considerable difficulties still exist in fabrication of three-dimensional (3D) photonic crystals and metamaterials, both fields exhibit considerable experimental progress 4,5 . On the other hand, on the theoretical side these fields are believed to be complementary but mutually exclusive. Photonic crystal effects typically occur in artificial optical media which are periodically structured on the scale of free space light wavelength l, while electromagnetic metamaterials are required to be structured (not necessarily in a periodic fashion) on the scale, which is much smaller than the free space wavelength of light. For example, in metal nanowire-based hyperbolic metamaterials 6 schematically shown in Fig. 1A the inter-wire distance must be much smaller than l. Here we report experimental realization of 3D ''photonic hyper-crystals'' which bridge this divide by combining the most interesting properties of hyperbolic metamaterials and photonic crystals.Our concept of the photonic hyper-crystal 7 is based on the fact that dispersion law of extraordinary photons in hyperbolic metamaterials does not exhibit the usual diffraction limit. In such uniaxial metamaterials the in-plane e xy and out-of-plane e z components of the dielectric permittivity tensor have opposite signs (e.g. the metal wire array hyperbolic metamaterial shown in Fig. 1A may have e z , 0 and e xy . 0 8 ), so that the photon wave vector components k i are not bounded at a given frequency of light v. Existence of large k-vector modes in a broad range of frequencies is responsible for such unusual effects as hyperlens-based super-resolution imaging [8][9][10][11] and broadband divergence of photonic density of states in hyperbolic metamaterials 12 . On the other hand, this also means that periodic modulation ...

Transformation optics gives rise to numerous unusual optical devices, such as novel metamaterial lenses and invisibility cloaks. Very recently Mattheakis et al. [1] have suggested theoretical design of an optical waveguide based on a network of Luneburg lenses, which may be useful in sensing and nonlinear optics applications. Here we report the first experimental realization of such Luneburg waveguides. We have studied wavelength and polarization dependent performance of the waveguides. Explosive development of elecromagnetic metamaterials and transformation optics (TO) produced such novel and fascinating optical devices as perfect lenses [2], hyperlenses [3-5], invisibility cloaks [6-9], and perfect absorbers [10]. Very recently Mattheakis et al. [1] have suggested a theoretical design of an optical waveguide based on a network of TO-based lenses, such as a Luneburg lens [11], and suggested that such a waveguide may be useful in sensing and nonlinear optics applications. Here we report the first experimental realization of such Luneburg waveguides, which operate in the visible

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