Experimental demonstration of water based tunable metasurface

Abstract

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.

Toroidal Dipole Mode Observation In Situ

“…Toroidal dipole is inherent to the system of toroidal topology and appears due to specific configuration of current density. Namely, poloidal currents, flowing along the meridians on the torus‐like objects, generate magnetic moments that circulate inside the torus, and altogether they create toroidal moments oscillating along the torus main axis . Apparently, the main interest on toroidal moment is underpinned by their contribution to more promising anapole mode excitations that take place due to destructive interference between electric and toroidal multipoles of the same order, leading to such effects as strong field localization inside the even point‐like sources and invisibility to external observer .…”

“…It is very convenient for applications due to controllable properties, namely adaption to any geometry in volume and mechanical, thermal, and gravitational tunability, dramatic dependence of permittivity on the temperature and pressure, and, obviously, ecologically friendliness. In fact, water is an available elementary component for laboratory prototyping of electromagnetic effects, such as Mie resonance in all‐dielectric particles, phase diagrams in nanophotonics, perfect absorbers, etc . Since water is a liquid‐state dielectric, we have a chance to “look into” water metamolecules to find out what exactly happens with electromagnetic fields inside dielectrics as well as to confirm the theory of Mie scattering on dielectric particles and even legitimize Maxwell's theory describing the behavior of electromagnetic waves in dielectrics.…”

“…Namely, poloidal currents, flowing along the meridians on the toruslike objects, generate magnetic moments that circulate inside the torus, and altogether they create toroidal moments oscillating along the torus main axis. [14][15][16][17][18][19][20][21][22] Apparently, the main interest on toroidal moment is underpinned by their contribution to more promising anapole mode excitations that take place due to destructive interference between electric and toroidal multipoles of the same order, leading to such effects as strong field localization inside the even point-like sources and invisibility to external observer. [10][11][12][13]17,[23][24][25][26][27][28][29][30][31][32] The works of the last decade point out to feasibility of this effect in structures from microwaves to optics and demonstrate such effects as novel types of transparency, [23] optical invisibility, [27,33] and cloaking.…”

“…In fact, water is an available elementary component for laboratory prototyping of electromagnetic effects, such as Mie resonance in all-dielectric particles, [18] phase diagrams in nanophotonics, [43] perfect absorbers, etc. [14,[44][45][46][47][48] Since water is a liquid-state dielectric, we have a chance to "look into" water metamolecules to find out what exactly happens with electromagnetic fields inside dielectrics [49] as well as to confirm the theory of Mie scattering on dielectric particles and even legitimize Maxwell's theory describing the behavior of electromagnetic waves in dielectrics.…”

Cylindrical-water-resonator-based ultra-broadband microwave absorber

“…Recently, water has also become a hot spot in the design of all-dielectric metamaterials [33][34][35], which can support electric or/and magnetic resonance through properly tailoring the shape or orientation of dielectric resonators. And because of the fluidity of water, tunable all-dielectric metamaterials are easy to be achieved [36,37]. Different from other microwave dielectrics, the imaginary part of water's permittivity, ε″, is quite large in microwave band, making it shows high dielectric loss and suitable for design of EM absorber with high absorptivity.…”