Infrared camouflage and radar compatible stealth structure based on metamaterial

Chang Yang; Chang Yang; Hao Guo; Huicong Chang; Yanchen Qu; Yanchen Qu; Lin Xiao; Lin Xiao; Lin Xiao

doi:10.1364/OME.488234

1. Introduction

Stealth technology that can simultaneous decrease the target characteristic of visible, infrared, radar, etc. is an important approach [1–3] to against the combined use of various means of detectint. Due to the continuous development and extensive application of infrared and radar surveillance, infrared and radar compatible stealth is a current research hotspot [4–6]. In the research field of infrared and radar compatible stealth, the main contradiction is that radar and infrared stealth materials have opposite requirements for electromagnetic wave absorption response [7]. However, the difference between infrared wavelength and radar wavelength makes it possible for radar and infrared compatible stealth.

Currently, some of the means to achieve radar and infrared compatible stealth use composite materials, such as conductive polymer [8], nanomaterials [7,9], doped semiconductor materials [3,10], etc. Studies on infrared and radar compatible stealth based on metamaterials have also been reported. It is usually realized by constructing radar low-pass filter type FSS with low emissivity and radar metamaterial abosrber [11]. In addition, based on the characteristics of the substrate material, compatible stealth materials can also have the characteristics of flexibility or visible light transparency [12,13,14]. Multispectral compatible stealth work has also been reported recently [15,16,17]. Qiu et al. used one-dimensional photonic crystals to achieve the characteristics of structural color, low infrared emission, high microwave transmittance, and selective thermal radiation. One-dimensional photonic crystal combined with a metamaterial absorber realizes multi-band compatible stealth of optics, infrared and radar [15]. In many compatible stealth schemes, a low infrared emissivity structure is designed to achieve the suppression of infrared radiation, which is very effective for a simple infrared radiation background. However, for real and complex backgrounds such as jungle and wilderness, the infrared radiation has obvious difference and is patchy. In this condition, target with a single fixed emissivity even with lower emissivity would highly exposed to IR detector due to its obvious contrast with background. Infrared image segmentation, similar with optical digital camouflage, is the main means to realize infrared camouflage in complex backgrounds. Also, a suitable IR camouflage pattern can enable the fusion of target and backgrounds [18,19].

In this study, a new design strategy of infrared camouflage and radar compatible stealth metamaterials (IRSM) is presented. These FSSs with different emissivity values are arranged into a pattern similar to the visible camouflage, and the surface with infrared camouflage distribution can be blended into the complex infrared background. Instead of designing complex resonant structures, by the combination of the equivalent circuit model and particle swarm optimization algorithm, the absorptivity of the radar metamaterial abosrber based on the square ring resonant element is greater than 90% in 4.5 GHz-18 GHz, and the radar waves through the IRCL are absorbed and dissipated through ohmic loss. The combination of two layers of metamaterial structure realizes the multi-band stealth capability of infrared camouflage and radar absorbtion.

2. Theory and design

The schematics illustration of the proposed compatible was shown in Fig. 1. There are three parts with different infrared emissivity in the IRCL, where the dark blue part represents the FSS₁, the light blue part represents the FSS_2, and the white part represents the surface coverage without ITO film. The greater number of red squiggles, the stronger infrared radiation intensity in that section. The radar wave (orange squiggles) that passes through the IRCL is absorbed by the sandwich type radar metamaterial abosrber which acted as radar absorbing layer with polymethacrylimide (PMI) foam and back reflection layer. In the radar absorbing layer, the resonant elements are the square ring structure obtained by patterning ITO transparent conductive film. The dielectric constant of polyethylene terephthalate (PET) substrate and PMI foam are 3(1 + 0.002i) (eps_PET) and 1.09(1 + 0.0014i) (eps_PMI). Periodic boundary conditions were used in the simulation, and the back reflection layer was set as perfect electric conductor to reduce the simulation time. Our proposed structure was calculated by commercial simulation software (CST Studio 2017).

Fig. 1. The principle of IRSM proposed in this study to achieve multispectral stealth.

Download Full Size | PDF

Metal, ITO transparent conductive film and other similar materials with high conductivity have the characteristics of low infrared emissivity and high radar reflectivity. Taking ITO film with 10 Ω/sq as an example, its simulated radar wave reflection characteristics (green curve) are shown in Fig. 2(a). Almost all incoming radar waves are reflected and easily exposed to radar detection. The continuous film is designed to FSS so that radar wave can efficiently pass through the layer and then be absorbed by the radar metamaterial abosrber, reducing the reflective properties of the target. As shown in Fig. 2(a), when the periodic length (p₁= 0.62 mm) of FSS is fixed, the transmission rate of radar waves in the high-frequency part will gradually become lower as the side length of the square becomes longer. The IR emissivity value of FSS can be calculated from the equation [20]:

(1)$${\varepsilon _{\textrm{fss}}}\textrm{ = }{\varepsilon _{\textrm{sq}}}{\eta _{\textrm{sq}}}\textrm{ + }{\varepsilon _{\textrm{sub}}}(1\textrm{ - }{\eta _{\textrm{sq}}})$$

here ${\varepsilon _{\textrm{sub}}}$ is the emissivity of PET substrate (${\varepsilon _{\textrm{sub}}}$=0.9). The emissivity of FSS (${\varepsilon _{\textrm{fss}}}$) decreases as the percentage of square area (${\eta _{\textrm{sq}}}$) increases. The parameters should be optimized to ensure that the radar transmittance of the target band is high enough and also has a suitable infrared emissivity. Since the infrared temperature distribution in the actual background environment is not uniform, the infrared camouflage surface with irregular distribution of infrared emissivity like the camouflage pattern is well integrated with the background environment. Two kinds of FSS structures were selected to constitute the IRCL as shown in Fig. 1. The radar wave transmission rate of FSS₁ (magenta curve) and FSS₂ (blue curve) are greater than 98% within 18 GHz, which ensures that the radar waves pass through the IRCL and are absorbed by the radar metamaterial abosrber efficiently, thus achieving low RCS for the target. The theoretical calculated values of emissivity are 0.25 (FSS₁), 0.55 (FSS₂), 0.93 (No FSS), and the area share of each part is 0.51, 0.31, 0.18. The different infrared radiation ability of each part of IRCL makes the target less distinguishable from the background in the infrared detector.

Fig. 2. (a) The simulated result of the transmittance of FSS as a function of w; (b) The equivalent circuit (EC) model of ring square structure; (c) Iteration results of the particle swarm optimization algorithm; (d) The absorption and reflection result obtained by CST and equivalent circuit model.

Download Full Size | PDF

A sandwich metamaterial absorbers is used to achieve efficient broadband microwave absorption performance, which can be represented by an analog circuit [21]. The lumped parameters of complex resonant pattern units are difficult to obtain. For simple structures such as crosses, circles, and square rings, the lumped parameter values can be calculated by the theoretical model. As shown in Fig. 2(b), the equivalent circuit of square ring resonant structures are a series circuit with resistance (R_s), inductance (L), and capacitance (C), whose values are mainly determined by the geometric parameters of the square ring and the square resistance. For square ring structures, R_s, L, C of the theoretical model can be calculated by [22–24]:

(2)$${R_s} = {R_g}\frac{{{p^2}}}{{{w^2} - {{(w - a)}^2}}}$$

(3)$$\textrm{L} = \frac{{{\alpha _L}{\textrm{Z}_0}p}}{{\omega \lambda }}\left\{ {\ln \left( {\csc \frac{{\pi \textrm{a}}}{{2p}}} \right) + } \right.\frac{1}{2}{({1 - {\beta_L}^2} )^2}\left. {\frac{{2A\left( {1 - \frac{{{\beta_L}^2}}{4}} \right) + 4{\beta_L}^4{A^2}}}{{\left( {1 - \frac{{{\beta_\textrm{L}}^2}}{4}} \right) + 2A{\beta_L}^2\left( {1 + \frac{{{\beta_L}^2}}{2} - \frac{{{\beta_L}^4}}{8}} \right) + 2{A^2}{\beta_L}^6}}} \right\}$$

(4)$$\textrm{C} = \varepsilon \frac{{4\ast {\alpha _L}p}}{{{\textrm{Z}_0}\omega \lambda }}\left\{ {\ln \left( {\csc \frac{{\pi \textrm{a}}}{{2p}}} \right) + } \right.\frac{1}{2}{({1 - {\beta_L}^2} )^2}\left. {\frac{{2A\left( {1 - \frac{{{\beta_L}^2}}{4}} \right) + 4{\beta_L}^4{A^2}}}{{\left( {1 - \frac{{{\beta_\textrm{L}}^2}}{4}} \right) + 2A{\beta_L}^2\left( {1 + \frac{{{\beta_L}^2}}{2} - \frac{{{\beta_L}^4}}{8}} \right) + 2{A^2}{\beta_L}^6}}} \right\}$$

where λ is wavelength in free space, ω is angle frequency of radar wave, $\textrm{A} = 1/\sqrt {1 - {{(p/\lambda )}^2}}$, ${\alpha _\textrm{C}}\textrm{ = }2\mathrm{\ast }a/p$, ${\alpha _\textrm{L}}\textrm{ = w}/p$, ${\beta _\textrm{C}} = \sin (\frac{{\pi (p - \textrm{w})}}{{2p}})$, ${\beta _\textrm{L}} = \sin (\frac{{\pi \textrm{a}}}{{2p}})$, $\varepsilon \textrm{ = }\frac{{\textrm{ep}{\textrm{s}_{\textrm{PET}}}\textrm{ + ep}{\textrm{s}_{\textrm{PMI}}}}}{2}$. The metallic layer of the back reflectivity layer is considered as a short-circuited wire. The dielectric layer is equivalent to the transmission line with characteristic impedance, Zd₁ and Zd₂ are the characteristic impedance of PET and PMI. Z₁, Z₂ and Z_in are the equivalent input impedance of each layer of the radar metamaterial abosrber. The impedance of each dielectric layer is related to its dielectric constant (eps_PMI, eps_PET) and thickness (h₁, h₂). Z₀ is the free space intrinsic impedance, which is equal to 377 Ω.

We combined the particle swarm optimization algorithm [13,25] with the equivalent circuit model of the square ring resonant absorber to optimize the structure and obtain better absorption performance. The fitness function (FF) in the particle swarm optimization algorithm is:

(5)$$\textrm{FF} ={-} \int\limits_{f = 4GHz}^{f = 18GHz} {(A(f) - 0.9)\ast {A^ \ast }(f)}$$

(6)$${A^\ast } = \left\{ \begin{array}{ll} 0,\begin{array}{{cc}} {}&{A(f) \ge 0.9} \end{array}\\ 1,\begin{array}{{cc}} {}&{A(f) < 0.9} \end{array} \end{array} \right.$$

where $A(f )= 1 - R(f )- T(f )= 1 - S_{11}^2 - S_{21}^2$,S₁₁ and S₂₁ are reflection/transmission coefficients, and S₂₁ is neglected because the transmission is extremely low. Our target is to have a minimum absorption efficiency above 0.9 in the range of 4 to 18 GHz. Therefore, A(f)-0.9 is used as a judgment condition.

The particle swarm optimization algorithm uses 25 particles and 100 iterations to search for the optimal solution and the range of parameter optimization is listed in Table 1. In Fig. 2(c), color dots represent the fitness values of the 20 particles in each iteration. The black curve with blue dot represents the “global best” records, which was the optimal solution result since the first iteration. The initial global best fitness value is 25.6. After 63 iterations, the global best fitness value goes down to 0.063 and the optimization is reaching convergence. The absorption bandwidth ranges from 4.3 to 18 GHz. The computer resources are i7-10700@ CPU 2.9 GHz, RAM 32 Gb. The time consumed for 100 iterations is about 5.2 s in MATLAB. Based on the commercial full-wave simulation software, the time required for one simulation is about 31 s. For the same number of particles and iteration number, the total number of calculations is 2500 and the total calculation time is about 21.6 hours. The combination of the parametric resonant absorbing structure and the optimization algorithm can achieve intelligent and fast optimization. Compared with the full-wave simulation, this method greatly reduces the optimization time. According to the optimization results, we confirm the dimension of the structure in Fig. 1. p = 5.2 mm, a = 5 mm, w = 0.3 mm, h₁= 5.5 mm, R_ring= 12 Ω/sq. From Fig. 2(d), the absorption performance obtained from the equivalent circuit model (black curve) is in good agreement with the results of the full-wave simulation (red curve). Adding FSS₁ and FSS₂ to the optimized radar metamaterial abosrber, the simulation results of the respective absorption performance are shown in the blue curve (FSS₁) and magenta curve (FSS₂). It can be seen that the FSS layer has little effect on the absorption performance of radar metamaterial abosrber. For FSS₁, the absorption performance in the high frequency band is reduced. For FSS₂, there is almost no effect on absorption performance. The camouflage FSS pattern cannot be directly simulated due to its complex structure. However, due to the efficient transmittance of each component, the performance of the metamaterial absorber covering the IRCL can be remainded.

Table 1. The range of values of each parameter

View Table

Wide incidence angles and polarization insensitivity are necessary for stable metamaterial performance in practical applications. The simulation results in TE and TM modes of the absorptivity at incidence angles θ from 0° to 60° and the absorptivity at polarization angles φ from 0° to 90° are shown in Fig. 3. As can be seen in Fig. 3(a), when the electric field polarization angle φ changes, the absorbing performance is basically unchanged. The high symmetry of the square ring structure gives the metamaterial polarization insensitive property. For the TE mode, the absorption capacity of low and medium frequency part decreases significantly, while the absorption performance of high frequency part remains unchanged. For the TM polarization, the overall absorption band shifts to the high frequency band. The absorption efficiency of the absorber at 30° incidence angle remains the same for both polarization modes. And at 45° incidence angle, it can still maintain more than 80% of the absorption efficiency.

Fig. 3. (a) The microwave absorptivity of the radar metamaterial abosrber versus frequency and polarization angle (φ). Simulated absorptivity under different incident angles θ for TE (c) and TM (d) modes.

Download Full Size | PDF

3. Result and discussion

To experimentally validate the simulated absorption performance and infrared camouflage property of the proposed IRSM, the sample with dimensions of 180 mm × 180 mm × 5.8 mm was fabricated by three ITO/PET films and PMI foam, as shown in Fig. 4(a), the inset is an optical micrograph of FSS₂ in IRCL. The top and second continuous ITO film were patterned by laser etching technology. The side of the second ITO/PET film without ITO film was sprayed medium green. Another bottom ITO/PET film acted as a back reflectivity layer. Since the visible light transmittance of ITO/PET is very high, the sample appears green on the surface of the radar absorber layer below the IRCL.

Fig. 4. (a) The photograph of the IRSM sample. The inset is the Optical microscopic image of the FSS₁. (b-f) The infrared temperature images of the heating plate, PET film, ITO/PET film, IRCL and IRSM.

Download Full Size | PDF

The infrared temperature images of heating plate, PET film, ITO/PET film and IRCL are shown in Fig. 4 (b-e). The number in the upper right corner of the picture is the average temperature in the test area. The temperature of the heating plate is 50.5 °C (test results of thermocouples is 50.9 °C), the infrared temperature of PET film is 47.5 °C with emissivity about 0.83, and the temperature of ITO conductive film is 27.1 ℃ with emissivity about 0.08. The average temperature of the IRCL is 30.1 ℃ and the infrared temperature of the three parts is 35.3 ℃, 42.7 ℃ and 47.3 ℃, respectively. The measured radiation temperature in Fig. 5(e) was used to estimate the infrared emissivity of the FSS, calculated as [10]:

(7)$$\varepsilon \textrm{ = }\frac{{T_{\textrm{IR}}^4\textrm{ - }T_{\textrm{AM}}^4}}{{T_{\textrm{RE}}^4\textrm{ - }T_{\textrm{AM}}^4}}$$

where $T_{\textrm{IR}}^4$, and are $T_{\textrm{RE}}^4$ the infrared temperature, $T_{\textrm{AM}}^4$ ambient temperature and real temperature respectively. The ambient temperature is 25 °C and the true temperature of IRCL is 50.7 °C. The calculated emissivity of FSS₁/FSS₂ by Eq. (7) are 0.27/0.548. The experimental emissivity values are in agreement with the theoretical emissivity values. Figure 4(e) shows the infrared temperature of the whole sample. Due to the good adiabatic performance of PMI foam, the infrared temperature of the whole device is further reduced to 28.1 °C, 35.9 °C and 38.4 °C respectively. The three temperatures of the IRCL have an obvious temperature ladder, which can better integrate with the complex infrared temperature distribution in the background.

Fig. 5. Temperature distribution of thermal models with different emissivity values.

Download Full Size | PDF

When the emissivity of the object surface is different, the ability to radiate heat is not the same. The effect of different emissivity on the model surface temperature is analyzed in a simple model using comsol multiphysics simulation software. As shown in Fig. 5, the model includes a metal layer (4 mm) and PMI foam layer (5.8 mm). The emissivity of the upper boundary is set to 0.93, 0.46 (the average emissivity of IRCL) and 0.27 to indicate the different material properties of PET, IRCL and FSS₁. The heat flux of the lower boundary is 150 W/m². The same natural convection conditions were set for the upper boundary, and both sides of the model were set as thermal insulation. At the same heat flow input, when the thermal equilibrium is reached, the surface temperature of PET film, IR camouflage film and ITO/PET film are 311 K, 315 K and 321 K respectively. Compared with ITO film, the infrared camouflage film can radiate more energy to the environment. This prevents an increase in the temperature of the stealthy target surface due to heat accumulation.

An arch system, including an Agilent (N5232A) network analyzer and two pairs of antenna speakers operating at 4-8 GHz and 8-18 GHz, was used to measure microwave absorptivity. Figure 6(a) shows the experimental test results of the TE/TM mode (black curve/ red curve) of the proposed IRSM and the simulation result of the RMA with FSS₂ at an incidence angle of 8°. Due to the symmetry of the basic unit of the FSS, even though the pattern of the IRCL is asymmetric, this causes only a slight difference in the transmission rate of the radar waves with different polarization patterns. Thus, for both TE (black curve) and TM (red curve) modes, the experimental results of absorption performance are the same. The absorbing capacity of the sample is greater than 90% from 4.65-18 GHz, which is consistent with the simulation results (blue curve). The measured absorption results of IRSM at different oblique incidence angles for TE and TM modes are shown in Figs. 6(b) and (c), respectively. The experimental results are in accordance with the simulated absorption spectra shown in Fig. 3. As the incidence angle continues to increase, the absorption performance of IRSM is decreasing. In thre low frequency part, the absorption performance of IRSM is very sensitive to incident angle. For TM mode, the proposed IRSM still can maintain a relatively high absorption capacity. Within the range of an incident angle of 45°, the absorptivity exceeds 80% for TE and TM modes in most band ranges. The experiment result indicated that the proposed IRSM can keep a stable absorption property when incident angle changes.

Fig. 6. (a) Comparison of the experiment and simulation absorptance for the IRSM at an incident angle of 8°. The inset is the arch system. Experiment absorption results of the proposed IRSM for different oblique incidence angles with (b) TE and (c) TM polarizations.

Download Full Size | PDF

4. Conclusions

In this paper, an infrared camouflage and radar compatible stealth metamaterials are designed and fabricated. The IRCL features an infrared camouflage pattern and different infrared emissivity regions are 0.27, 0.55 and 0.93. IRCL can radiate more energy into the environment to avoid temperature increases. The combination of the equivalent circuit model and the particle swarm optimization algorithm can achieve intelligent and fast optimization. Compatible stealth metamaterials based on a simple square ring resonance structure can also achieve absorption rates greater than 90% from 4.5GHz to 18GHz. The combination of two layers of metamaterial structure realizes the multi-band stealth capability of infrared camouflage and radar absorption.

Funding

National Natural Science Foundation of China (21905301).

Acknowledgment

This work was supported by National Natural Science Foundations of China (NSFC).

Disclosures

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

References

1. W. Pan, M. He, X. Bu, Y. Zhou, B. Ding, T. Huang, S. Huang, and S. Li, “Microwave absorption and infrared emissivity of helical polyacetylene@multiwalled carbon nanotubes composites,” J. Mater. Sci.: Mater. Electron. 28(12), 8601–8610 (2017). [CrossRef]

2. N. Baranwal and S. P. Mahulikar, “Review of infrared signature suppression systems using optical blocking method,” Def. Technol. 15(3), 432–439 (2019). [CrossRef]

3. H. Xing, X. Cao, X. Ji, D. Tan, and Y. Gan, “Microwave Absorption and Infrared Stealth Properties of Ni-doped ZnO/Al Composites,” Nano 11(04), 1650047 (2016). [CrossRef]

4. L. Yuan, C. Huang, J. Liao, C. Ji, J. Huang, Y. Wang, and X. Luo, “A Dynamic Thermal camouflage metadevice with microwave scattering reduction,” Adv. Sci. 9(22), 2201054 (2022). [CrossRef]

5. X. Feng, M. Pu, F. Zhang, R. Pan, S. Wang, J. Gong, R. Zhang, Y. Guo, X. Li, X. Ma, and X. Luo, “Large-Area Low-Cost Multiscale-Hierarchical Metasurfaces for Multispectral Compatible Camouflage of Dual-Band Lasers, Infrared and Microwave,” Adv. Funct. Mater. 32(36), 2205547 (2022). [CrossRef]

6. W. Gu, J. Tan, J. Chen, Z. Zhang, Y. Zhao, J. Yu, and G. Ji, “Multifunctional bulk hybrid foam for infrared stealth, thermal insulation, and microwave absorption,” ACS Appl. Mater. Interfaces 12(25), 28727–28737 (2020). [CrossRef]

7. M. Zhang, Y. Zhou, M. He, T. Zhang, and X. Bu, “Helical polysilane wrapping onto carbon nanotube: Preparation, characterization and infrared emissivity property study,” RSC Adv. 6(9), 7439–7447 (2016). [CrossRef]

8. W. J. Ma, C. H. Tang, P. He, X. H. Wu, Z. K. Cui, S. L. Lin, X. Y. Liu, and Q. X. Zhuang, “Morphology-Controlled Fabrication Strategy of Hollow Mesoporous Carbon Spheres@f-Fe2O3 for Microwave Absorption and Infrared Stealth,” ACS Appl. Mater. Interfaces 14(30), 34985–34996 (2022). [CrossRef]

9. Z. Zhang, M. Xu, X. Ruan, J. Yan, J. Yun, W. Zhao, and Y. Wang, “Enhanced radar and infrared compatible stealth properties in hierarchical SnO2@ZnO nanostructures,” Ceram. Int. 43(3), 3443–3447 (2017). [CrossRef]

10. S. Zhong, W. Jiang, P. Xu, T. Liu, J. Huang, and Y. Ma, “A radar-infrared bi-stealth structure based on metasurfaces,” Appl. Phys. Lett. 110(6), 063502 (2017). [CrossRef]

11. C. Zhang, J. Yang, W. Yuan, J. Zhao, J. Dai, T. Guo, J. Liang, G. Xu, Q. Cheng, and T. Cui, “An ultralight and thin metasurface for radar-infrared bi-stealth applications,” J. Phys. D: Appl. Phys. 50(44), 444002 (2017). [CrossRef]

12. N. K. Lee, J. S. Lim, I. J. Chang, H. Bae, Nam Mo, J. Y. Cho, and H. Hee, “Flexible assembled metamaterials for infrared and microwave camouflage,” Adv. Opt. Mater. 10(11), 2200448 (2022). [CrossRef]

13. C. Yang, S. Niu, H. Chang, Y. Wang, Y. Feng, Y. Zhang, G. Li, S. Chen, Y. Qu, and L. Xiao, “Thermal infrared and broadband microwave stealth glass windows based on multi-band optimization,” Opt. Express 29(9), 13610–13623 (2021). [CrossRef]

14. H. Li, H. Yuan, F. Costa, Q. Cao, W. Wu, and A. Monorchio, “Optically transparent water-based wideband switchable radar absorber/reflector with low infrared radiation characteristics,” Opt. Express 29(26), 42863–42875 (2021). [CrossRef]

15. H. Zhu, Q. Li, C. Tao, Y. Hong, Z. Xu, W. Shen, S. Kaur, P. Ghosh, and M. Qiu, “Multispectral camouflage for infrared, visible, lasers and microwave with radiative cooling,” Nat. Commun. 12(1), 1805 (2021). [CrossRef]

16. Y. Huang, Y. Zhu, B. Qin, Y. Zhou, R. Qin, P. Ghosh, M. Qiu, and Q. Li, “Hierarchical visible-infrared-microwave scattering surfaces for multispectral camouflage,” Nanophotonics 11(16), 3613–3622 (2022). [CrossRef]

17. M.S. Ergoktas, G. Bakan, E. Kovalska, M. Said Ergoktas, G. Bakan, E. Kovalska, L. W. L. Fevre, R. P. Fields, P. Steiner, X. X. Yu, O. Salihoglu, S. Balci, V. I. Fal’ko, K. S. Novoselov, R. A. W. Dryfe, and C. Kocabas, “Multispectral graphene-based electro-optical surfaces with reversible tunability from visible to microwave wavelengths,” Nat. Photonics 15(7), 493–498 (2021). [CrossRef]

18. I. Chang, T. Kim, N. Lee, J. Nam, J. Lim, M. Yun, and H. Cho, “Multispectral Optical Confusion System: Visible to Infrared Coloration with Fractal Nanostructures,” ACS Appl. Mater. Interfaces 14(24), 28337–28347 (2022). [CrossRef]

19. J. K. Zhang, D. P. Zhao, J. C. Wang, et al., “Thermal infrared pattern painting based on photonic crystals,” Acta Optica Sinic 36(12), 1216001 (2016). [CrossRef]

20. S. Zhong, L. Wu, T. Liu, J. Huang, W. Jiang, and Y. Ma, “Transparent transmission-selective radar-infrared bi-stealth structure,” Opt. Express 26(13), 16466–16476 (2018). [CrossRef]

21. C. Yang, H. C. Chang, L. Xiao, and Y. C. Qu, “Visible and NIR transparent broadband microwave absorption metamaterial based on silver nanowires,” Opt. Mater. (Amsterdam, Neth.) 131, 112464 (2022). [CrossRef]

22. F. Ruiz-Perez, S.M. López-Estrada, R.V. Tolentino-Hernández, and F. Caballero-Briones, “Carbon-based radar absorbing materials: A critical review,” J. Sci.: Adv. Mater. Devices 7(3), 100454 (2022). [CrossRef]

23. Y. Huang, J. Luo, M. Pu, Y. Guo, Z. Zhao, X. Ma, X. Li, and X Luo, “Catenary Electromagnetics for Ultra-Broadband Lightweight Absorbers and Large-Scale Flat Antennas,” Adv. Sci. 6(7), 1801691 (2019). [CrossRef]

24. Y. Guo, X. Ma, M. Pu, X. Li, Z. Zhao, and X. Luo, “High-Efficiency and Wide-Angle Beam Steering Based on Catenary Optical Fields in Ultrathin Metalens,” Adv. Opt. Mater. 6(19), 1800592 (2018). [CrossRef]

25. J. Li, L. Bao, S. Jiang, Q. Guo, D. Xu, B. Xiong, G. Zhang, and F. Yi, “Inverse design of multifunctional plasmonic metamaterial absorbers for infrared polarimetric imaging,” Opt. Express 27(6), 8375–8386 (2019). [CrossRef]

Parameter	Max	Min
P	3.2 mm	4.8 mm
a	2.0 mm	3.0 mm
w	1.6 mm	2.4 mm
h ₁	0.7 mm	1.2 mm
R_ring	8 Ω/sq	100 Ω/sq

Infrared camouflage and radar compatible stealth structure based on metamaterial

Abstract

1. Introduction

2. Theory and design

3. Result and discussion

4. Conclusions

Funding

Acknowledgment

Disclosures

Data availability

References

Data availability

Cited By

Figures (6)

Tables (1)

Equations (7)

Optical Materials Express