Wire metamaterials: physics and applications

From 1D to 3D: a new route to fabricate tridimensional structures via photo-generation of silver networks

A time-saving and low-cost method is established to construct stacked 3D structures through the combination of bottom-up and top-down techniques which enables us to create building blocks freely and to precisely adjust the matrix feature.

Impact of filling ratio on subwavelength optical imaging using metallic nanolens of different geometries

A nanolens based on a metallic nanorod has been considered as a prospective candidate for transporting subwavelength information. Such a lens is tuned to a particular frequency by tailoring the length of the nanorod. In this paper, we have investigated the impact of filling ratio on the subwavelength imaging capabilities of such a lens. Through full-wave electromagnetic simulation, we have demonstrated that the imaging performance of a silver (Ag) nanorod array depends not only on the length and periodicity but also on the filling ratio or the radius of the nanorod. We have studied this impact for nanorods having different cross-sectional shapes such as cylindrical and triangular and examined their performances for various filling ratios.

Realization of deep subwavelength resolution with singular media

The record of imaging resolution has kept being refreshed in the past decades and the best resolution of hyperlenses and superlenses so far is about one out of tens in terms of wavelength. In this paper, by adopting a hybrid concept of transformation optics and singular media, we report a broadband meta-lens design methodology with ultra-high resolution. The meta-lens is made of subwavelength metal/air layers, which exhibit singular medium property over a broad band. As a proof of concept, the subwavelength imaging ability is demonstrated over a broad frequency band from 1.5-10 GHz with the resolution varying from 1/117 to 1/17 wavelength experimentally.

Subwavelength imaging in the visible range using a metal coated carbon nanotube forest

We demonstrate subwavelength imaging in the visible range by using a metal coated carbon nanotube forest. Under 532 nm illumination, a 160 nm separated double slit is resolved. This corresponds to the resolution of 0.3 wavelength. By controlling the growing conditions and with the help of the microtoming technique, we made a dense carbon nanotube forest layer of 400 nm thickness. The metal coated carbon nanotube forest, acting as a wire medium nanolens, delivers imaging information including details in the evanescent fields near the objects.

Imaging performance of finite uniaxial metamaterials with large anisotropy

Metamaterials with extreme anisotropy overcome the diffraction limit by supporting the propagation of otherwise evanescent waves. Recent experiments in slabs of wire media have shown that images deteriorate away from the longitudinal Fabry-Perot resonances of the slab. Existing theoretical models explain this using nonlocality, surface waves, and additional boundary conditions. We show that image aberrations can be understood as originating from cavity resonances of uniaxial media with large local axial permittivity. We apply a simple cavity resonator model and a transfer matrix approach to replicate salient experimental features of wire media hyperlenses. These results offer avenues to reduce observed imaging artefacts, and are applicable to all uniaxial media with large magnitude of the axial permittivity, e.g., wire media and layered media.

Arbitrary control of electromagnetic flux in inhomogeneous anisotropic media with near-zero index

We propose a method to control electromagnetic flux in an almost arbitrary way in wavelength and subwavelength scales. The capability of subwavelength flux control is enabled by the evanescent waves induced in a class of inhomogeneous anisotropic media with a near-zero permittivity component. By designing the spatial profile of the other permittivity component in such inhomogeneous media, the flow and distribution of energy flux can be conveniently manipulated. This method provides another approach to efficiently control electromagnetic flux in nonmagnetic media.

Homogenization of quasi-1d metamaterials and the problem of extended bandwidth

We derive approximate analytical expressions for the effective permittivity tensor of two-phase metamaterials whose geometry is close to one-dimensional (quasi-one-dimensional metamaterials). Specifically, we consider the metamaterial made of parallel slabs with width given by a linear or parabolic function. Using our approach, the design of epsilon-near-zero, ultra-low and high refractive index metallodielectric metamaterials with extended bandwidth has been demonstrated. In addition, generalizations to the three-dimensional case and some limitations of the presented technique are briefly considered.

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.

Optimization of radiative heat transfer in hyperbolic metamaterials for thermophotovoltaic applications

Using our recently developed method we analyze the radiative heat transfer in micron-thick multilayer stacks of metamaterials with hyperbolic dispersion. The metamaterials are especially designed for prospective thermophotovoltaic systems. We show that the huge transfer of near-infrared thermal radiation across micron layers of metamaterials is achievable and can be optimized. We suggest an approach to the optimal design of such metamaterials taking into account high temperatures of the emitting medium and the heating of the photovoltaic medium by the low-frequency part of the radiation spectrum. We show that both huge values and frequency selectivity are achievable for the radiative heat transfer in hyperbolic multilayer stacks.