Metasurfaces possess excellent capabilities to flexibly manipulate electromagnetic waves in multiple frequency domains, which show great potential application in multispectral stealth. Herein, a broadband surface waves coupler based on the design of thin Pancharatnam-Berry (PB) phase gradient metasurfaces (PGMs) of thickness 0.12λ0 is proposed to reduce infrared emission and microwave reflection simultaneously. Low infrared emission results from the high filling ratio of the indium-tin-oxide (ITO) on the surface, and low microwave reflection results from the conversion from propagating waves to surface waves. Intriguingly, this design is also capable of acting as a simple circular polarized (CP) discriminator because orthogonal CP waves are coupled into surface waves propagating along opposite directions. A proof-of-concept prototype is simulated and measured to validate the effectiveness of our methodology. The results indicate that the broadband surface waves coupler shows low infrared emissivity less than 0.28 from 3 to 14 µm and has microwave reflection reduction larger than 10 dB in 7.3-9.5 GHz. The exceptional performances of the proposed broadband surface waves coupler make us believe that our design offers an alternative strategy for multispectral stealth and multifunctional application.

A visible-light-transparent metasurface has been designed to achieve infrared (IR)–radar stealth. An optically transparent material, indium tin oxide was chosen in preference to other low-IR-emissivity metals to achieve camouflage compatibility for the IR–radar stealth material. In addition, flexible polyethylene terephthalate was adopted as the dielectric material to in order to benefit from its visible light transparency; its softness could also improve its application prospects. The fabricated structure exhibited a strong absorptivity of over 90% from 8.265 GHz to 17.65 GHz and a low IR emissivity of less than 0.3 in the region of 3–14 μ m. The results demonstrated that the metasurface was polarization independent and it was still able to maintain 90% of its absorptivity with an oblique incidence of 20°. The good consistency between the experimental and simulated results verified that the proposed metasurface can be practically applied in multifunctional stealth technology.

Metasurfaces have shown promising applications in radar-infrared compatible stealth because of its superior electromagnetic wave control capabilities, but, to date, the majority of designs still suffer from the defects of large thickness, limited working bandwidth, relatively high infrared emissivity and so on. Here, an exotic phase gradient metasurface (PGM) is proposed to achieve low microwave reflection and low infrared emission concurrently, which has a small thickness of about 0.10λ0. The microwave reflection reduction larger than 10 dB in 14-20 GHz is attributed to the anomalous reflection for arbitrary LP incident waves, and the infrared emissivity less than 0.28 from 3 to 14 µm is due to the indium-tin-oxide (ITO) with low infrared emissivity and high filling ratio. Also, the designed PGM can also realize beam deflection for orthogonal CP waves because of the meta-atoms' isotropic characteristics. Our methodology is fully verified by numerous simulations and experiments and may open a new avenue for radar-infrared compatible stealth research.

An optically transparent broadband metamaterial absorber (MA) containing an air layer and a water layer is proposed, which can absorb broad-band microwave and reduce infrared radiation at the same time. As a proof, a structure consisting of indium tin oxide (ITO) frequency selective surface (FSS), air layer, water substrate and ITO backplane was firstly designed. The simulation reveal that the structure can absorb wideband microwave with an efficiency of over 90% in the 14.4 GHz to 39.4 GHz frequency band, and it is optically transparent. This is consistent with the experimental results. In addition, the use of the water circulation system can significantly reduce the infrared radiation, thereby achieving infrared stealth. Due to its versatility and excellent performance, the proposed design is expected to find extensive applications in multi-spectrum stealth, such as glass windows for stealth devices, camouflage, etc.

In this paper, an optically transparent coding metasurface structure based on indium tin oxide (ITO) thin films with simultaneously low infrared (IR) emissivity and microwave scattering reduction is proposed. To this end, two ITO coding elements which can reflect 0° and 180° phase responses are firstly designed. Based on these two elements, four coding sequences with different scattering patterns are designed. Three of them can realize anomalous reflections and the fourth can realize random diffusion of normal incident electromagnetic (EM) waves. A prototype of the random diffusion coding metasurface was fabricated and measured. The experimental results show that for normal incident EM waves, at least 10dB backward scattering reduction from 3.8GHz to 6.8GHz can be achieved, and the structure is polarization insensitive. The averaged transmittance of visible light through the coding metasurface reaches up to 72.2%. In addition, due to the high occupation ratio of ITO on the outside of the coding metasurface, a low IR emissivity of about 0.275 is obtained. Good consistency between the experiment and simulation results convincingly verifies the coding metasurface. Due to its multispectral compatibility, the proposed coding metasurface may find potential applications in multi-spectral stealth, camouflage, etc.

In this article, we propose the design of a multispectral metasurface (MSM), which can simultaneously achieve quite good optical transparency, low infrared (IR) emissivity, and wideband microwave absorption. To this end, optically transparent materials were used in the MSM design, including indium tin oxide, polyethylene terephthalate, and polymethyl methacrylate. The MSM is composed of three functional layers: a frequency-selective surface (FSS) on the top, a resistively absorbing layer in the middle and a complete conducting sheet at the bottom. Because of large occupation ratio of conducting area and the low-pass property of the FSS, electromagnetic waves are allowed to penetrate through it into the middle absorbing layer, simultaneously with low surface IR emissivity. A prototype was designed, fabricated, and measured. Both the simulation and experiment results show that the MSM can achieve strong absorption of > 90% in 12.03-29.43 GHz and low IR emissivity of about 0.3 in 3.0-14.0 mu m simultaneously. Moreover, the average optical transparency is higher than 90%. Because of the excellent multispectral compatibility, the MSM may find applications in electromagnetic protection, stealth technologies, etc.

In this paper, we propose the design of an optically transparent metasurface with simultaneously wideband microwave absorption and low infrared (IR) emissivity. To this end, two optically transparent functional layers are firstly designed using indium-tin-oxide (ITO), which can suppress IR emission and achieve wideband microwave absorption, respectively. The two functional layers are then combined together to construct the multispectral metasurface. By properly tuning the structural parameters and sheet resistance of ITO, a wide microwave absorption band can be achieved with absorption higher than 90%. Low IR emissivity of about 0.30 is obtained by controlling the occupation ratio of ITO on the front side structure of the metasurface. A prototype was fabricated and measured. The measured results show that the averaged transmittance of visible light through the metasurface reaches up to 62.4% and the high-efficiency microwave absorption can be achieved in 11.2-33.9 GHz, with absorption rate higher than 90%. Good consistency between the experiment and simulation results convincingly verifies the metasurface. Due to its multispectral compatibility, the proposed metasurface may find potential applications in multi-spectral stealth, camouflage, etc.

To get low transmittance in mid-infrared atmospheric windows(3-5μm)and far-infrared atmospheric windows(8-14μm),we designed a double frequency infrared frequency selective surface(FSS).This FSS is composed of two ring structures–the outer side of the structure is a hexagon and inner side is a circle.The simulation results of CST electromagnetic software show that the average transmittance of the FSS in both mid and far infrared atmospheric windows is less than 5%;in addition,the two stopbands in infrared wavelengths are realized.The filtering mechanism of the frequency selective surface is analyzed based on the method of surface current model analysis.The structure forms a symmetrical current mode through the coupling between the unit in the screen,which enhances the scattering-field and decreases the transmission rate,forming a stopband in the corresponding band.The simulation results show that the structure has polarization stability and good angle stability for TE electromagnetic waves with different incident angles.In addition,the dielectric layer thickness and loss tangent have little effect on transmission properties,and dielectric constant has a great effect on transmission properties.

为实现覆盖中、远红外两个大气窗口的低透射率,采用六边形环复合“单钺”型短臂与十字结构共振器相结合的思路,设计了一种可调节的、“双环—双屏”三明治结构的频率选择表面.CST电磁软件仿真结果表明,在3～5 μm,8～14μm两个红外大气窗口内的平均透射率低于1.9％,可以对中、远红外电磁波有较好的抑制传输效果,并且有优越的偏振稳定性和入射角度稳定作用;通过利用表面电流分析法与等效介质原理法,以不同的角度阐述了频率选择表面结构的滤波机理.并通过仿真计算的方式,探究出电介质层属性与单元结构参数对频率选择表面的滤波效果有较大影响,研究结果对后续实验有重要的指导作用.

A multiple working mechanism metasurface (MWMM) is proposed to reduce infrared emission and the microwave reflection simultaneously. In addition, it has good oblique performance and achieves compatibility-stealth for infrared (IR)- radar. For these purposes, the first working mechanism of MWMM which is designing stacking two arrays which is ITO as an alternative without other opaque metals is for the visible transparence. The second working mechanism of MWMM which is designing a frequency selective surface (FSS) made of ITO arrays instead of other low infrared emissivity metals achieves the characteristic of IR-stealth. The third and last working mechanism of MWMM are the microwave absorption and the phase cancellation respectively to reduce reflection for microwave-camouflage. The tailored MWMM exhibited a broadband the efficiency larger than 10 dB from 7.21 GHz and 18.89GHZ and low IR emissivity is about 0.3 in the region of 3-14 mu m with high IR-reflection over than 80% under the same region. And comparing with the simple absorber, the part-absorptive principle for infrared will reduce temperature for this MWMM under the higher conditions. This is needed urgently for IR-radar compatible-stealth application.