We demonstrate that spectrally diverse multiple magnetic dipole resonances can be excited in all-dielectric structures lacking rotational symmetry, in contrast to conventionally used spheres, disks or spheroids. Such multiple magnetic resonances arise from hybrid Mie-Fabry-Pérot modes, and can constructively interfere with induced electric dipole moments, thereby leading to novel multi-frequency unidirectional scattering. Here we focus on elongated dielectric nanobars, whose magnetic resonances can be spectrally tuned by their aspect ratios. Based on our theoretical results, we suggest all-dielectric multimode metasurfaces and verify them in proof-ofprinciple microwave experiments. We also believe that the demonstrated property of multimode directionality is largely responsible for the best efficiency of all-dielectric metasurfaces that were recently shown to operate across multiple telecom bands.

Originally introduced in the early 2010's, the idea of smart environments through reconfigurable intelligent surfaces (RIS) controlling the reflections of the electromagnetic waves has attracted much attention in recent years in preparation for the future 6G. Since reconfigurable intelligent surfaces are not based on increasing the number of sources, they could indeed pave the way to greener and potentially limitless wireless communications. In this paper, we design, model and demonstrate experimentally a millimeter wave reconfigurable intelligent surface based on an electronically tunable metasurface with binary phase modulation. We first study numerically the unit cell of the metasurface, based on a PIN diode, and obtain a good phase shift and return loss for both polarizations, over a wide frequency range around 28.5 GHz. We then fabricate and characterize the unit cell and verify its properties, before fabricating the whole 10 cm×10 cm reconfigurable intelligent surface. We propose an analytical description of the use that can be done of the binary phase RIS, both in the near field (reflectarray configuration) and in the far field (access point extender). We finally verify experimentally that the designed RIS works as expected, performing laboratory experiments of millimeter wave beamforming both in the near field and far field configuration. Our experimental results demonstrate the high efficiency of our binary phase RIS to control millimeter waves in any kind of scenario and this at the sole cost of the energy dissipated by the PIN diodes used in our design.

A simple dynamically tunable metasurface (two-dimensional metamaterial) operating at microwave frequencies is developed and experimentally investigated. Conceptually, the simplicity of the approach is granted by reconfigurable properties of unit cells partially filled with distilled water. The transmission spectra of the metasurface for linear and circular polarizations of the incident wave were experimentally measured under the metasurface rotation around a horizontal axis. The changes in the transmission coefficient magnitude up to 8 dB at 1.25 GHz are reported while rotating the metasurface by the 90° angle. The proposed approach manifests the cheap and accessible route for the electromagnetic wave control in the microwave region with the help of metasurfaces.

−1 ; d) Q factor of the fundamental magnetic dipole mode Q md for the same wavelength and r/L = 0.55; e) References for material parameters; f) Anisotropic, in-plane, and out-of-plane component, respectively; g) High-resistivity silicon; h) Measured data (Figure 2c).

All-dielectric reciprocal metasurface based on bianisotropic scatterers operating at microwave frequencies is demonstrated experimentally. Experimental studies of a single bianisotropic particle supporting both electric and magnetic Mie-type resonances are performed, and reveal that the particle with a broken symmetry exhibits different back-scattering for the opposite excitation directions. A metasurface composed of the all-dielectric bianisotropic particles is fabricated and experimentally investigated in the frequency range of 4–9 GHz. The measured data demonstrate that the metasurface is characterized by different reflection phases when being excited from the opposite directions. At the frequency 6.8 GHz, the metasurface provides a 2π phase change in the reflection spectrum with the amplitude close to 1.

A composite medium consisting of two sublattices of dielectric spherical particles of high permittivity and different radii embedded in a dielectric matrix of smaller permittivity are considered. It has been shown that such a composite medium reveals properties of an isotropic double negative media (DNG) in a limited frequency range, when resonance oscillations of HIII mode in one kind of particles and EIII mode in another kind of particles are excited simultaneously. The EIII resonance and the HIII resonance give rise to the magnetic dipole momentum and the electric dipole momentum correspondingly. Averaging the magnetic momentum and the electric momentum over the cells belonging to the appropriate spherical particles gives the negative permittivity and permeability. The model of diffraction of a plane electromagnetic wave on a dielectric sphere is presented and compared with the mixing rule based consideration. The results obtained are rather close. Distribution of the electromagnetic wave outside the sphere is calculated. Influence of the dispersion of the sphere size and the dielectric permittivity on the effective parameters of the DNG material is estimated.

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