![]() Semireal case T SR: (red, dashed) real case T R (blue, solid). Left: operational wavelength λ 1 = 1.437 μ m right: operational wavelength λ 1 = 1.389 μ m. The incident beam is Gaussian with σ k = 1 / 25 ⋅ 2 π / λ ( FWHM ≈ 19 μ m ). ![]() Bottom: calculated beam displacements Δ of the transmitted field at the output facet of the MM slab as a function of the incident-beam’s mean wave-vector component k x 0. Top right: schematic illustration of the direction of beam propagation normal to the isofrequency curve around the mean wave vector k ( 0 ) (lossless medium assumed). For R e ( n ) < 0 the expected shift is negative, with Δ < 0 (red, dashed path). In geometrical optics, a material with R e ( n ) > 0 leads to a positive shift of the beam Δ > 0 (blue, dotted path) along the surface. Top left: schematic picture of ray optical refraction and beam shift at the interfaces of an isotropic and homogeneous slab for oblique incidence. Ultimately the main conclusion to be drawn is that a negative index of refraction is by no means a sufficient criterion to achieve negative refraction and/or perfect imaging.įigure 9(Color online) Refraction of wide beams. All our physical predictions are backed by rigorous numerical calculations and the agreement is almost perfect. In particular, we discuss both the effect of the specific dispersion relation and the losses on the imaging properties. In detail, we study the effect of these peculiarities on imaging and refraction of finite beams. We show that both refraction and diffraction properties are strongly spatially and temporally dispersive and they can even change sign. As an example, we apply it to the fishnet structure: one of the most prominent and best studied design approaches to date. This general approach holds for any optical material, in particular, for all MMs in question. Imaging properties follow straightforwardly from that data. Most of the relevant optical parameters, such as refraction and diffraction coefficients, can be derived from this relation. Instead we prove that the dispersion relation of normal modes in these MMs provides all the required information. We show that this approach is pointless for realistic MMs. On this basis suggestions for a perfect lens, exploiting this negative refractive index have been put forward by taking advantage of geometrical optics arguments. To date, apart from identifying chiral properties of very specific configurations, this is primarily done in retrieving an effective refractive index-mostly-only for normal incidence. For the light of given colour, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant in the given pair of media. An inevitable first step toward this goal is the evaluation of the optical properties of specifically designed MMs. The incident ray, the refracted ray and the normal to the interface of the two transparent media at the point of incidence all lie in the same plane. In the past several years, optical metamaterials (MMs) have attracted a considerable deal of interest because it may be anticipated that their properties can be shaped to an unprecedented extent relieving optics from some of its natural limitations.
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