Artificially structured hyperbolic metamaterials (HMMs) - uniaxial materials with opposite signs of permittivity for ordinary and extraordinary waves - are one of the most attractive classes of metamaterials. Their existing in nature counterpart natural (homogeneous) hyperbolic materials (NHMs) has several advantages but has not yet been analyzed extensively. Here, based on literature-available data on permittivity as a function of wavelength, we review materials with naturally occurring anisotropy of permittivity in specific wavelength ranges. We suggest the best choice of materials that may act as NHMs depending on the wavelength, strength of the dielectric anisotropy (SDA), and losses.

Metamaterials offer new unusual electromagnetic properties, which have already been demonstrated, and many postulated new functionalities are yet to be realized. Currently, however, metamaterials are mostly limited by narrow band behavior, high losses, and limitation in making genuinely 3D materials. In order to overcome these problems an overlap between metamaterial concepts and materials science is necessary. Engineered self‐organization is presented as a future approach to metamaterial manufacturing. Using directional solidification of eutectics, the first experimental realization of self‐organized particles with a split‐ring resonator‐like cross section is demonstrated. This unusual morphology/microstructure of the eutectic composite has a fractal character. With the use of TEM and XRD the clear influence of the atomic crystal arrangement on the microstructure geometry is presented. The materials obtained present very high anisotropy and can be obtained in large pieces. Metallodielectric structures can be created by etching and filling the space with metal. The next steps in the development of self‐organized materials exhibiting unusual properties are discussed.

Metallodielectric materials with plasmonic resonances at optical and infrared wavelengths are attracting increasing interest, due to their potential novel applications in the fields of photonics, plasmonics and photovoltaics. However, simple and fast fabrication methods for three‐dimensional bulk plasmonic nanocomposites that offer control over the size, shape and chemical composition of the plasmonic elements have been missing. Here, such a manufacturing method and examples of experimental realizations of volumetric isotropic nanocomposites doped with plasmonic nanoparticles that exhibit resonances at visible and infrared wavelengths are presented. This method is based on doping a low‐melting dielectric material with plasmonic nanoparticles, using a directional glass‐solidification process. Transmission‐spectroscopy experiments confirm a homogenous distribution of the nanoparticles, isotropy of the material and resonant behavior. The phenomenon of localized surface plasmon resonance is also observed visually. This approach may enable rapid and cost‐efficient manufacturing of bulk nanoplasmonic composites with single or multiple resonances at various wavelength ranges. These composites could be isotropic or anisotropic, and potentially co‐doped with other chemical agents, in order to enhance different optical processes.

Due to the development of novel manufacturing technologies and the increasing availability of nano‐/micromaterials, plasmonics has become an emerging field in photonics research. Although the fabrication of metallic elements has already been widely demonstrated, the development of 3D plasmonic materials is progressing slowly. This paper reports the development of a self‐organized, 3D nanoplasmonic eutectic composite that exhibits localized surface plasmon resonance at 595 nm. This eutectic composite is produced by directional solidification with the micro‐pulling‐down method and consists of a 3D, multiscale network of silver, nanometer‐thick, micron‐long sheets, and triangular cross‐section microprecipitates embedded in a crystalline bismuth oxide matrix. Annealing at 600 °C further refined the structure and introduced metallic nanoparticles that exhibited plasmonic resonance in the optical region of the spectrum. This is the first demonstration of plasmonic behavior in a eutectic‐based composite, which is engineered specifically for this purpose using a self‐organization mechanism.

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Sodium aluminophosphate glasses were evaluated for their bone repair ability. The glasses belonging to the system 45Na2O–xAl2O3‐(55‐x)P2O5, with x = (3, 5, 7, 10 mol%) were prepared by a melt‐quenching method. We assessed the effect of Al2O3 content on the properties of Na2O–Al2O3–P2O5 (NAP) glasses, which were characterized by density measurements, DSC analyses, solubility, bioactivity in simulated body fluid and cytocompatibility with MG‐63 cells. To the best of our knowledge, this is the first investigation of calcium‐free Na2O–Al2O3–P2O5 system glasses as bioactive materials for bone tissue engineering.

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Metastable defects in semiconductor materials have been well known for decades, but have only recently started to attract attention for their potential applications in information technology. Here, we describe active and passive nanoplasmonic materials with optically active metastable defects that can be switched on or off by cooling with or without laser illumination, respectively. To the best of our knowledge, this is the first report of metastable defects in either passive or active nanoplasmonic materials, and, more generally, in non-semiconducting materials. The nanocomposites are made of a sodium-boron-phosphate glass matrix doped with silver nanoparticles (nAg) or co-doped with nAg and Er3+ ions by NanoParticle Direct Doping method. We further show that the different origins of the two types of defect-related luminescence behaviour are attributable to either a metal-glass defect (MG1) or a metal-glass-rare-earth ion defect (MGR1). Such materials could potentially be used for data writing and erasing using laser illumination with a ‘tight’ focus such as direct laser writing.