We provide a numerical tool to quantitatively study the impact of nonlocality arising from free electrons in metals on the optical properties of metallo-dielectric multilayers. We found that scattering matrices are particularly well suited to take into account the electron response through the application of the hydrodynamic model. Though effects due to nonlocality are, in general, quite small, they, nevertheless, can be important for very thin (typically below 10 nm) metallic layers, as in those used in structures characterized by exotic dispersion curves. Such structures include those with a negative refractive index, hyperbolic metamaterials, and near-zero index materials. Higher wave vectors mean larger nonlocal effects, so that it is not surprising that subwavelength imaging capabilities of hyperbolic metamaterials are found to be sensitive to nonlocal effects. We find in all cases that the inclusion of nonlocal effects leads to at least a 5% higher transmission through the considered structure.

This study aims to give a general theory that enables the design of flat lenses based on hyperbolic metamaterials. We derive a lens equation that is demonstrated to involve the curvature of the dispersion relation. Guided by this theory, hyperbolic lenses of focal length ranging from zero to a few wavelength are simulated. High transmission efficiency is also obtained by reducing the amount of metal compared to the dielectric material.

The aim of Moosh is to provide a complete set of tools to compute all the optical properties of any multilayered structure: reflection, transmission, absorption spectra, as well as gaussian beam propagation or guided modes. It can be seen as a semi-analytic (making it light and fast) solver for Maxwell's equations in multilayers. It is written in Octave/Matlab, available on Github and based on scattering matrices, making it perfectly stable. This software is meant to be extremely easy to (re)use, and could prove useful in many research areas like photovoltaics, plasmonics and nanophotonics, as well as for educational purposes for the large number of physical phenomena it can illustrate.

In the framework of the hydrodynamic model describing the response of electrons in a metal, we show that arrays of very narrow and shallow metallic slits have an optical response that is influenced by the spatial dispersion in metals arising from the repulsive interaction between electrons. As a simple Fabry-Perot model is not accurate enough to describe the structure's behavior, we propose to consider the slits as generalized cavities with two modes, one being propagative and the other evanescent. This very general model allows to conclude that the impact of spatial dispersion on the propagative mode is the key factor explaining why the whole structure is sensitive to spatial dispersion. As the fabrication of such structures with relatively large gaps compared to previous experiments is within our reach, this work paves the way for future much needed experiments on nonlocality.arXiv:1501.05765v2 [physics.optics]

We show that any metallo-dielectric multilayer with a hyperbolic dispersion relation can actually be characterized by a complex effective index. This refractive index, extracted from the complex Bloch band diagram, can be directly linked to the super-resolution of a flat lens made of this socalled indefinite medium. This allows for a systematic optimization of the lens design, leading to structures that are outperforming state-of-art flat lenses. We show that, even when fully taking absorption into account, our design provides super-resolved images for visible light up to a distance of one wavelength from the lens edge.PACS numbers: 78.67.Pt, 42.25.Fx, 78.20.Ci Since the seminal work of Sr J. B. Pendry, who proposed a perfect lens of unlimited resolution, intensive efforts have been made to realize reliable metamaterials that could make this concept effective [1]. Beating the optical diffraction limit requires to conceive bulk metamaterials presenting both electric and magnetic permittivities (ǫ and µ) equal to -1. These slabs of -1 refractive index are however particularly difficult to realize at optical frequencies since their building blocks (split rings resonators, wires) are not sizable at the nanometer scale [2]. An alternative approach has recently emerged with feasible metal-dielectric multilayers, referred to as indefinite metamaterials, which operate at ultraviolet frequencies [3]. These highly anisotropic media present hyperbolic photonic dispersion surfaces in the k-space, which induces enhanced optical properties [4][5][6][7][8] Fig. 1. Consequently, both propagating and evanescent waves emitted by a source decompose onto propagating waves in the hyperbolic medium, so that the subwavelength details are efficiently transported through the lens. This principle has been experimentally demonstrated in the far-field space with a hyperlens that presents a spherical shape [9][10][11]. Planar indefinite hyperbolic metamaterials have also been theoretically predicted to form subwavelength images bonded at the output interface of the lens when the canalization regime is reached [12,13]. Others results have moreover shown that light focalization is also possible in the near-field and a lens equation for these hyperbolic lenses has been derived [14][15][16][17]. Other progress towards negative index metamaterials have been reported theoretically and demonstrated experimentally with coupled plasmonic waveguide structures that resemble indefinite metamaterials [18,19]. The latter results have in particular shown that these metamaterials behave as -1 effective index flat lenses that make images for ultraviolet light [19]. This effective index has been evidenced by tracking the refracted angles of a beam launched for various incident angles through a stack of silver and TiO 2 thin films. According to the authors, subwavelength resolution has not been achieved because of the optical losses, that are known to reduce the efficiency of metamaterials lenses. However, very little is known so far on the exact role of ...

This paper reports on dielectric properties of ternary mixtures involving sodium chloride (NaCl) and sucrose (C12H22O11) dissolved into water (H2O). Broadband electromagnetic characterizations of such mixtures at various concentrations were performed, evidencing a dual behavior made of conductive effects at low frequencies and dipolar relaxation at microwave frequencies. Conductive and dielectric properties resulting from these both effects were integrated into predictive models for variations of Cole–Cole model parameters. Based upon this modelling, an innovative microwave-based sensor able to retrieve concentrations of both sodium chloride and sucrose in ternary aqueous solutions was introduced, designed, realized and assessed. The proposed sensor shows an error lower than 5.5% for concentration ranges of 0 to 154 mmol/L for sodium chloride and 0 to 877 mmol/L for sucrose.

It can be shown that negative refraction cannot occur in one-dimensional photonic crystals oriented as in[1].

When a thin structure in which negative refraction occurs (a metallo-dielectric or a photonic crystal) is illuminated by a beam, the reflected and transmitted beam can undergo a large negative lateral shift. This phenomenon can be seen as an interferential enhancement of the geometrical shift and can be considered as a signature of negative refraction. c 2017 Optical Society of America OCIS codes: 000.0000, 999.9999.It has been recently shown that when a beam is illuminating a slab presenting negative permittivity and permeability the reflected and transmitted beam could undergo a large negative lateral shift [1]. It has then been suggested that some of these lateral shifts are linked to the negative refraction which occurs when light enters the structure [2,3]. In the present letter, we show for the first time that a large lateral shift explicitely due to negative refraction can be obtained using a very thin slab of photonic crystal, thus confirming the previous assumption. Here we have not used metamaterials designed to present negative permittivity and permeability as in [1], which definitely shows that negative refraction alone is responsible for the negative shift.In previous works, large lateral shifts have already been obtained using a photonic crystal, but they were either positive [4,5] or negative but due to a guided mode excited by a grating [6].The lateral shift associated to negative refraction has already been proposed as a signature of that phenomenon [7] in a case where the thickness of the structure is larger than the waist of the incident beam. The lateral shift is in that case purely geometrical. We show in this paper that the large negative lateral shift is finally an interferential enhancement of the geometrical lateral shift. It occurs in very thin structures compared to the waist, and it can be used to characterize negative refraction.In order to get a physical picture of the phenomenon, let us begin by considering a lossless metallo-dielectric multilayer. Such a structure can be considered as a 1D photonic crystal. It is now well-known that negative refraction may occur when TM polarized light enters such a structure [8]. The transparency of that type of structure is due to the excitation of coupled resonances : either coupled guided modes supported by the metallic slabs, or Fabry-Perot resonances of the cavity constituted by the dielectric layers. Here we consider the second case, when the field is propagative in the dielectric layer.Negative refraction occurs when the dielectric layers are thin and when their relative permittivity is high enough, so that the field is more localized in the metal.We have thus chosen ǫ m = −4.43, corresponding to the real part of the permittivity of silver at 400 nm and ǫ d = 5.3 so that ǫ d > |ǫ m |. The thickness of the dielectric (resp. metallic) layers is h d = 0.0979λ (resp. h m = 0.0975λ).The component of the Poynting vector parallel to the interfaces of the metallo-dielectric structure, P x , controls the direction in which light will propagate in t...