Enhanced transmission through a sub-wavelength aperture: resonant approaches employing metamaterials

In this paper, we propose a number of resonant metamaterial-based approaches to enhance the power transmission through sub-wavelength apertures. The extraordinary transmission beyond the diffraction limit is usually obtained using setups that rely on covers supporting proper surface plasmon polaritons or leaky waves. However, the actual implementation in real-life applications of these structures is strongly limited by their large transverse extension. After briefly reviewing the aforementioned limitations, we present in the paper new setups based on resonant approaches, characterized by covers whose transverse dimensions are of the same order of magnitude as the aperture size. The phenomenology of the enhanced transmission, the related theoretical aspects, the results of the numerical simulations and the successful experimental verification using the newly proposed setups are then presented in detail.