Equivalent circuit model for coupled complementary metasurfaces

Coupled complementary metasurfaces (CCMTS) exhibit a passband whose frequency is several times lower than that of the individual metasurface (MTS) passband frequency. In this paper we explain this phenomenon and propose a simple and accurate equivalent circuit for CCMTS comprised of slots and their Babinet complement, dipoles. An equivalent circuit is extracted from a coupled EFIE-MFIE equation using a synthetic basis function. The same procedure can be conveniently applied to any CCMTS. The model allows one to estimate the large downshift of resonant frequency and the bandwidth utilizing a simple formula. When used in a subresonant regime, the unit cell may have a dimension of a tenth of a free space wavelength with a moderate value of permittivity between the complementary layers

Dipole-slot-dipole metasurfaces

A complementary frequency selective surface (CFSS) can be formed on the basis of Babinet’s principle. It consists of an array of slots separated from an array of dipoles by a thin dielectric substrate. This study shows that by adding an extra layer of dipoles to a CFSS capacitance can be added to the structure, which leads to a decrease in its resonant frequency. This new structure is called a dipole-slot-dipole metasurface (MTS) and it has unit-cell dimensions of l/10 × l/10 × l/333, where l is representing the free space wavelength. The dipole-slot-dipole MTS has been fabricated and measured. The study also reports on its equivalent circuit; and the effects of the length of the dipoles on the added layer and their alignment on the pass band resonant frequency of the dipole-slot-dipole MTS

THz-photonics transceivers by all-dielectric phonon-polariton nonlinear nanoantennas

The THz spectrum (spanning from 0.3 to 30 THz) offers the potential of a plethora of applications, ranging from the imaging through non transparent media to wireless-over-fiber communications and THz-photonics. The latter framework would greatly benefit from the development of optical-to-THz wavelength converters. Exploiting Difference Frequency Generation in a nonlinear all dielectric nanoantenna, we propose a compact solution to this problem. By means of a near-infrared pump beam (at ω1), the information signal in the optical domain (at ω2) is converted to the THz band (at ω3= ω2- ω1). The approach is completely transparent with respect to the modulation format, and can be easily integrated in a metasurface platform for simultaneous frequency and spatial moulding of THz beams