Negative refraction in a metamaterial composed of pairs of nanowires

A metamaterial with an electromagnetically active single unit composed of two parallel nanowires was recently proposed by Sarychev and his collaborators. One layer of the anisotropic metamaterial contains a randomly distributed set of oriented wires that cover 10% of the layer surface. It was noted that a multilayer structure of the metamaterial should exhibit macroscopic negative refraction. Here, in the computer refraction experiment we confirm that expectation. In FDTD simulations we analyze propagation of near infrared light through the metamaterial slab. We simulate performance of a single layer illuminated normally and of a few layers illuminated at a small angle. Electric field of the illuminating Gaussian beam lies in the plane of incidence that is parallel to the direction of oriented pairs of wires. For a small angle of incidence we calculate two characteristics: the attenuation versus wavelength and the lateral shift of beam on the plane-parallel slab versus wavelength. According to our model, negative refraction should be observed for a narrow range of wavelengths around 2.85 μm. In simulations made for a single layer medium, negative refraction is observed for wavelengths λ from 1.55 to 2.1 μm, with Δλ/λ≈0.3. When the number of layers increases, the range of negatively refracted wavelengths becomes narrower. In the metamaterial slab composed of three layers attenuation of the Gaussian beam of wavelengths λ=1.2-1.55 μm and incident at 10° changes from -13 to -25 dB, respectively.