Water-based metamaterial absorbers for optical transparency and broadband microwave absorption

Abstract

Naturally occurring water is a promising candidate for achieving broadband absorption. In this work, by virtue of the optically transparent character of the water, the water-based metamaterial absorbers (MAs) are proposed to achieve the broadband absorption at microwave frequencies and optical transparence simultaneously. For this purpose, the transparent indium tin oxide (ITO) and polymethyl methacrylate (PMMA) are chosen as the constitutive materials. The water is encapsulated between the ITO backed plate and PMMA, serving as the microwave loss as well as optically transparent material. Numerical simulations show that the broadband absorption with the efficiency over 90% in the frequency band of 6.4–30 GHz and highly optical transparency of about 85% in the visible region can be achieved and have been well demonstrated experimentally. Additionally, the proposed water-based MA displays a wide-angle absorption performance for both TE and TM waves and is also robust to the variations of the structure parameters, which is much desired in a practical application.

Optically transparent and very thin structure against electromagnetic pulse (EMP) using metal mesh and saltwater for shielding windows

“…The EM shielding mechanism of the saltwater layer is different from the metal mesh, in which the reflection mainly contributes to the total EM shielding 8 . A similar phenomenon of EM absorption was reported in the literature 20 .

Figure 3 ( a ) E-field distribution of the incident EM wave along with the thickness of the saltwater layer with a thickness of a half wavelength of the EM wave in saltwater ( ); SE of the planar saltwater in the C-band: ( b ) at different salinities ( t s = 10 mm), ( c ) at different thicknesses (S = 200 ppt); ( d ) SE of the four types of TEs in the C-band.

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“…The EM shielding mechanism of the saltwater layer is different from the metal mesh, in which the reflection mainly contributes to the total EM shielding 8 . A similar phenomenon of EM absorption was reported in the literature 20 .…”

Multi-Spectral Metasurface With High Optical Transparency, Low Infrared Surface Emissivity, and Wideband Microwave Absorption

“…With the rapid development of the technologies of metamaterials, the function of singlewaveband materials can no longer satisfy the needs of various applications. It is the mainstream to design the multispectral metasurfaces (MSMs) to apply under a variety of environments [11][12][13][14][15][16]. According to spectroscopy, microwave band, infrared (IR) band, and visible light band are the most commonly used region.…”

Generalised probe method to measure the liquid complex permittivity

“…a microfluidically controlled 3D printed waveguide [10]), metamaterials and absorbers (e.g. a water-based tunable metasurface [11], a tunable all-dielectric electromagnetic metamaterial [12], and water-based broadband metamaterial absorbers [13,14]).…”