Radio-shielding metamaterials transparent in the visible spectrum: approaches to creation

Abstract

The approaches to creation of the materials providing simultaneously high indicators of transparency in the visible spectrum and shielding in a wide radio frequency band are considered in this paper. The analysis and comparison of the main designs of such materials, as well as approaches to their creation, including multilayer and conductive mesh structures, is carried out. The results of our own theoretical studies of the disordered mesh structure are presented, which allow one to obtain a light transmission coefficient from 90 to 98 % in combination with an electromagnetic interference shielding efficiency from 50 to 65 dB. The best results practically achieved to date (shielding efficiency equal 45 dB in the range from 10 kHz to 20 GHz with a light transparency of more than 80 %) were obtained on mesh structures by photolithography, which is a significant limiting factor of this approach. The created multilayer structures show, in general, lower characteristics. However, the technology for their production is better scaled, and the optimization of the thicknesses and chemical composition of multilayer structures can significantly increase them. In this regard, technological aspects may come to the fore when taking into account the possibility of subsequent scaling of the technology and economic indicators when choosing an approach for the implementation of the materials with the required characteristics.

Optically Transparent and Highly Conductive Electrodes for Acousto-Optical Devices

“…Today, thin films based on tin indium oxide (ITO) are the most widely used [ 20 ]. Still, their usage is limited by the low ratio of transparency and electrical characteristics for many current tasks; the best samples of ITO coatings have a surface resistance of about 20 Ω/sq with transparency in the visible range of about 90% [ 21 ]. In addition, this material is expensive due to the depletion of global indium reserves [ 22 ], and requires high-temperature annealing to obtain a high Q factors ϕ s (ϕ s = T 550 10 /ρ s [ 23 ]), which complicate the production of high-quality transparent electrodes on flexible polymer substrates.…”

“…The geometry of such systems can be calculated in advance and specified during manufacture. Electrodes based on these structures have the best characteristics at the moment [ 21 ] in terms of the ratio of sheet resistance and transparency (3–5 Ω/sq with transparency of more than 85% [ 19 ]).…”

“…Currently, several approaches are being developed to produce such microgrids [ 21 , 26 ]. One of the general approaches consists of forming microgrooves with a high aspect ratio in an optically transparent material, such as quartz, into which metal, for example, silver or copper, is subsequently deposited [ 22 ].…”