An optically transparent multi-spectral stealth integrated metamaterial

Abstract

An optically transparent multi-spectral stealth integrated metamaterial belongs to the field of electromagnetic waves and new artificial electromagnetic materials. The present invention aims to solve the problem that existing stealth structures and materials cannot simultaneously have high transmittance of visible light, low emission in the infrared band, and broadband absorption in the microwave band. It is composed of a blank insert patterned impedance film layer, a first transparent substrate, an intermediate transparent medium layer, a second transparent substrate, and a second transparent conductive film from top to bottom; the blank insert patterned impedance film layer is composed of an array of N×M transparent patterned impedance film units; the transparent patterned impedance film unit is composed of a first transparent conductive film and four groups of blank insert array units. The optically transparent multi-spectral stealth integrated metamaterial of the present invention integrates radar stealth and infrared stealth functions into the same transparent patterned impedance film to achieve high transmittance in the visible light band, low emissivity in the infrared band, and broadband absorption in the microwave band.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic waves and new artificial electromagnetic materials. Background Art

[0002] With the rapid development of multi-spectral composite detection technology, single-band stealth is far from meeting the stealth requirements of modern warfare, and the development of multi-spectral stealth function integration technology is imperative.

[0003] At present, the most important means of detection in the military are radar detection and infrared detection. Therefore, designing a multi-spectral stealth structure that is compatible with radar-infrared stealth has become a research hotspot.

[0004] The requirements for material properties of radar stealth and infrared stealth are contradictory. Radar stealth requires that the material meet the characteristics of high absorption and low reflection in the microwave band, while infrared stealth requires that the material meet the characteristics of low absorption or low emissivity in the infrared band.

[0005] At the same time, it has become an inevitable and urgent need for multi-spectral stealth structures to take into account optical transparency properties for application in special environments such as aircraft cockpits.

[0006] Traditional stealth materials, such as composite nanofibers, conductive polymers, and doped oxide semiconductors, have been unable to meet the increasingly high multi-spectral stealth requirements. Moreover, they are usually opaque and cannot be used in optically transparent stealth devices.

[0007] As a new type of artificial electromagnetic surface, metasurface can flexibly manipulate the propagation of electromagnetic waves, light waves and plasma waves. The electromagnetic response in different spectral regions can be controlled by artificially designing the structural parameters of the metasurface. Based on transparent conductive materials and transparent dielectric materials, the introduction of metasurfaces to develop multi-spectral compatible structures is more conducive to the compatibility and realization of performance between different spectra.

[0008] For example, the paper "Flexible and Transparent Microwave-Infrared Bistealth Structure" published in Advanced Materials Technologies (Volume 4, Issue 8, 2014, Page 1900063) proposed a multi-spectral stealth structure based on a composite metasurface of an infrared shielding layer and a radar absorption layer, which can achieve more than 90% absorption in the range of 5.8-12.2GHz and an infrared emissivity of 0.23, but the multi-layer composite structure leads to a very low visible light transmittance of only about 20%. The paper "An Optically Transparent Sandwich Structure For Radar-Infrared Bi-Stealth" published in Infrared Physics & Technology (Volume 105, 2014, Page 103108) proposed a multi-spectral stealth structure using a sandwich type, which effectively improved the transmittance of the visible light band to 80%, while the relative bandwidth of the infrared emissivity of 0.52 and the absorptivity of more than 90% in the microwave band is 35.5%, which is not wide enough to meet the needs of practical applications.

[0009] Therefore, it is crucial to develop materials with variable loss dispersion to meet the conflicting parameter requirements of multi-spectral compatibility. At present, the development of an optically transparent multi-spectral stealth integrated metasurface that simultaneously takes into account high visible light transmittance, low infrared emission, and broadband absorption in the microwave band is still a difficult problem that needs to be solved urgently and has practical application significance. Summary of the invention

[0010] The present invention aims to solve the problem that existing stealth structures and materials cannot simultaneously have high visible light transmittance, low infrared emission and broadband absorption in the microwave band, and thus provide an optically transparent multi-spectral stealth integrated metamaterial.

[0011] An optically transparent multi-spectral stealth integrated metamaterial, which is composed of a blank insert patterned impedance film layer, a first transparent substrate, an intermediate transparent medium layer, a second transparent substrate and a second transparent conductive film in order from top to bottom;

[0012] The blank insert patterned impedance film layer is composed of N×M transparent patterned impedance film units in an array; N is ≥ 20 columns, and M is ≥ 20 rows; the side length of the transparent patterned impedance film unit is P;

[0013] The transparent patterned impedance film unit is composed of a first transparent conductive film and four groups of blank insert array units. Four groups of blank insert array units are arranged around the center of the transparent patterned impedance film unit; the four groups of blank insert array units are not covered by the first transparent conductive film;

[0014] The blank insert array unit is composed of three parallel blank inserts, and the parallel blank inserts are parallel to the side of the transparent patterned impedance film unit; assuming that the width of the blank insert is W, the width W of the three parallel blank inserts is 0.05mm-1mm, and the vertical distances from the inner side edges of the three parallel blank inserts to the center of the transparent patterned impedance film unit are L 1 , L 2 and L 3 , and L 1 1mm~10mm, L 2 -(L 1 +W)=0.5mm~10mm,L 3 -(L 2 +W)=0.5mm~10mm,P-2(L 3 +W)=0.5mm~10mm.

[0015] The beneficial effects of the present invention are:

[0016] First, the optically transparent multi-spectral stealth integrated metamaterial designed by the present invention can simultaneously take into account high transmittance in the visible light band (visible light transparency ≥ 70%), low emissivity in the infrared band (the average emissivity of 8μm to 14μm is 0.534), and broadband absorption in the microwave band (the absorption rate in the range of 8.9GHz to 16.4GHz is above 90%, and the absorption bandwidth is 59.3%), and has broad application scenarios in the multi-spectral stealth of optical windows.

[0017] Secondly, the present invention also has excellent properties such as low profile, good angle stability (it can achieve an absorption rate of more than 80% within the operating frequency band at an incident angle of 45° under TE waves and TM waves respectively) and polarization insensitivity, and has great application potential in the military.

[0018] Third, the present invention integrates radar stealth and infrared stealth functions into the same transparent patterned impedance film to achieve optically transparent dual stealth integrated design, with visible light transparency of not less than 70%, which can solve the shortcomings of low visible light transmittance and large thickness of optically transparent multi-spectral stealth structures in the prior art. At the same time, it overcomes the shortcomings of complex multi-spectral stealth structures and poor engineering feasibility in the prior art, making the present invention easy to process, low in cost, and with good engineering feasibility.

[0019] The present invention is used for an optically transparent multi-spectral stealth integrated metamaterial. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the optically transparent multi-spectral stealth integrated metamaterial of the present invention containing only one transparent patterned impedance film unit, 1 is a blank insert patterned impedance film layer, 2 is a first transparent substrate, 3 is an intermediate transparent medium layer, 4 is a second transparent substrate, and 5 is a second transparent conductive film;

[0021] Figure 2 for Figure 1 1-1 is a blank insert array unit, 1-1.1, 1-1.2 and 1-1.3 are three parallel blank inserts, P is the side length of the transparent patterned impedance film unit, W is the width of the blank insert, L 1 , L 2 and L 3 is the vertical distance between the inner side edges of the three parallel blank inserts and the center of the transparent patterned impedance film unit;

[0022] Figure 3 for Figure 1 Side view of h 1 is the thickness of the blank insert patterned impedance film, h 2 is the thickness of the first transparent substrate, h 3 is the thickness of the intermediate transparent medium layer, h 4 is the thickness of the second transparent substrate, h 5 is the thickness of the second transparent conductive film;

[0023] Figure 4 It is a schematic diagram of the structure of 3×3 transparent patterned impedance film units in the optically transparent multi-spectral stealth integrated metamaterial of the present invention;

[0024] Figure 5 The infrared emissivity spectrum of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 is obtained by testing the electromagnetic wave at vertical incidence;

[0025] Figure 6 This is a comparison diagram of the simulated results of the microwave band absorption curve of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 when the electromagnetic wave is vertically incident and the actual test results, 1 is the simulated microwave absorptivity, and 2 is the tested microwave absorptivity;

[0026] Figure 7 This is a simulation result diagram of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 0°;

[0027] Figure 8 This is a simulation result diagram of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 15°;

[0028] Fig. 9 This is a simulation result diagram of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 30°;

[0029] Fig.10 This is a simulation result diagram of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 45°;

[0030] Fig.11 The simulation results of the absorption rate of TE waves of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at different pitch angles are shown in Figure 1, where 1 is a pitch angle of 0°, 2 is a pitch angle of 15°, 3 is a pitch angle of 30°, and 4 is a pitch angle of 45°;

[0031] Fig.12 This is a simulation result diagram of the absorption rate of TM waves at different pitch angles of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1, where 1 is a pitch angle of 0°, 2 is a pitch angle of 15°, 3 is a pitch angle of 30°, and 4 is a pitch angle of 45°. DETAILED DESCRIPTION

[0032] Specific implementation method 1: Combination Figures 1 to 4 Specifically, the present embodiment is an optically transparent multi-spectral stealth integrated metamaterial, which is composed of a blank insert patterned impedance film layer, a first transparent substrate, an intermediate transparent medium layer, a second transparent substrate and a second transparent conductive film from top to bottom;

[0033] The blank insert patterned impedance film layer is composed of N×M transparent patterned impedance film units in an array; N is ≥ 20 columns, and M is ≥ 20 rows; the side length of the transparent patterned impedance film unit is P;

[0034] The transparent patterned impedance film unit is composed of a first transparent conductive film and four groups of blank insert array units. Four groups of blank insert array units are arranged around the center of the transparent patterned impedance film unit; the four groups of blank insert array units are not covered by the first transparent conductive film;

[0035] The blank insert array unit is composed of three parallel blank inserts, and the parallel blank inserts are parallel to the side of the transparent patterned impedance film unit; assuming that the width of the blank insert is W, the width W of the three parallel blank inserts is 0.05mm-1mm, and the vertical distances from the inner side edges of the three parallel blank inserts to the center of the transparent patterned impedance film unit are L 1 , L 2 and L 3 , and L 1 1mm~10mm, L 2 -(L 1 +W)=0.5mm~10mm,L 3-(L 2 +W)=0.5mm~10mm,P-2(L 3 +W)=0.5mm~10mm.

[0036] In this embodiment, ultraviolet laser micromachining equipment is used to etch the first transparent conductive film to obtain a blank insert.

[0037] The blank insert patterned impedance film layer described in this embodiment is an infinite periodic structure in which transparent patterned impedance film units are sequentially connected and arranged.

[0038] The beneficial effects of this embodiment are:

[0039] First, the optically transparent multi-spectral stealth integrated metamaterial designed in this specific embodiment can simultaneously take into account high transmittance in the visible light band (visible light transparency ≥ 70%), low emissivity in the infrared band (the average emissivity of 8μm to 14μm is 0.534), and broadband absorption in the microwave band (the absorption rate in the range of 8.9GHz to 16.4GHz is above 90%, and the absorption bandwidth is 59.3%), and has broad application scenarios in the multi-spectral stealth of optical windows.

[0040] Second, this specific implementation also has excellent properties such as low profile, good angle stability (it can achieve an absorption rate of more than 80% within the operating frequency band at an incident angle of 45° under TE waves and TM waves respectively) and polarization insensitivity, and has great application potential in the military.

[0041] Third, this specific implementation method integrates radar stealth and infrared stealth functions into the same transparent patterned impedance film to achieve optically transparent dual stealth integrated design, with visible light transparency of not less than 70%, which can solve the shortcomings of low visible light transmittance and large thickness of optically transparent multi-spectral stealth structures in the prior art. At the same time, it overcomes the shortcomings of complex multi-spectral stealth structures and poor engineering feasibility in the prior art, making the present invention easy to process, low cost, and good engineering feasibility.

[0042] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the thickness of the blank insert patterned impedance film layer is 0.01 μm to 3 μm. Other aspects are the same as the specific implementation method 1.

[0043] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the thickness of the first transparent substrate and the second transparent substrate are both 0.05 mm to 2 mm. The rest is the same as specific implementation method 1 or 2.

[0044] Specific implementation method 4: This implementation method is different from specific implementation methods 1 to 3 in that the thickness of the intermediate transparent medium layer is 1 mm to 8 mm. The rest is the same as specific implementation methods 1 to 3.

[0045] Specific implementation mode 5: This implementation mode is different from specific implementation modes 1 to 4 in that the thickness of the second transparent conductive film is 0.01 μm to 3 μm. The rest is the same as specific implementation modes 1 to 4.

[0046] Specific implementation example 6: This implementation example is different from specific implementation examples 1 to 5 in that the first transparent conductive film and the second transparent conductive film are made of aluminum-doped zinc oxide, fluorine-doped tin dioxide or indium tin oxide. Other aspects are the same as specific implementation examples 1 to 5.

[0047] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that the sheet resistance of the first transparent conductive film and the second transparent conductive film is 1Ω / sq to 400Ω / sq. Other aspects are the same as specific embodiments 1 to 6.

[0048] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the material of the first transparent substrate and the second transparent substrate are both made of one or a combination of polycarbonate, polyvinyl chloride, polydimethylsiloxane and polyethylene terephthalate. Other aspects are the same as specific embodiments 1 to 7.

[0049] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that: the material of the intermediate transparent medium layer is a transparent flexible polymer material and a transparent flexible inorganic material, or a composite of two; the relative dielectric constant of the intermediate transparent medium layer is 1 to 6. Other aspects are the same as specific embodiments 1 to 8.

[0050] Specific embodiment 10: This embodiment is different from specific embodiments 1 to 9 in that the relative dielectric constants of the first transparent substrate and the second transparent substrate are both 1 to 6. The rest is the same as specific embodiments 1 to 9.

[0051] The following examples are used to verify the beneficial effects of the present invention:

[0052] Embodiment 1:

[0053] An optically transparent multi-spectral stealth integrated metamaterial, which is composed of a blank insert patterned impedance film layer, a first transparent substrate, an intermediate transparent medium layer, a second transparent substrate and a second transparent conductive film in order from top to bottom;

[0054] The blank insert patterned impedance film layer is composed of N×M transparent patterned impedance film units in an array; N is greater than or equal to 20 columns, and M is greater than or equal to 20 rows; and the side length P of the transparent patterned impedance film unit is 14.7 mm;

[0055] The transparent patterned impedance film unit is composed of a first transparent conductive film and four groups of blank insert array units. Four groups of blank insert array units are arranged around the center of the transparent patterned impedance film unit; the four groups of blank insert array units are not covered by the first transparent conductive film;

[0056] The blank insert array unit is composed of three parallel blank inserts, and the parallel blank inserts are parallel to the side of the transparent patterned impedance film unit; assuming that the width of the blank insert is W, the width W of the three parallel blank inserts is 0.25 mm, and the vertical distances from the inner side edges of the three parallel blank inserts to the center of the transparent patterned impedance film unit are L 1 , L 2 and L 3 , and L 1 3.2mm, L 2 4.45mm, L 3 It is 6.5mm.

[0057] The thickness h of the blank insert patterned impedance film layer 1 =0.3μm.

[0058] The thickness of the first transparent substrate is h 2 =175μm; the thickness of the second transparent substrate is h 4 =125μm;

[0059] The thickness of the intermediate transparent medium layer is h 3 =2mm;

[0060] The thickness of the second transparent conductive film is h 5 =0.3μm.

[0061] The first transparent conductive film and the second transparent conductive film are both made of indium tin oxide.

[0062] The sheet resistance of the first transparent conductive film is 53Ω / sq; the sheet resistance of the second transparent conductive film is 5Ω / sq.

[0063] The materials of the first transparent substrate and the second transparent substrate are both polyethylene terephthalate.

[0064] The material of the intermediate transparent medium layer is polyvinyl chloride; the relative dielectric constant of the intermediate transparent medium layer is 2.4.

[0065] The relative dielectric constants of the first transparent substrate and the second transparent substrate are both 3.

[0066] The average visible light transmittance of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 is 70.18%.

[0067] Figure 5 The infrared emissivity spectrum of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 is obtained by testing when the electromagnetic wave is vertically incident. In the actual test, N=20 columns and M=20 rows are set. The low reflectivity curve of the infrared band 8μm~14μm is converted from the transmission curve and absorption curve measured by a Fourier transform infrared spectrometer. As can be seen from the figure, the average emissivity of the infrared band 8μm~14μm is 0.534, which has a low infrared emission property.

[0068] Figure 6 This is a comparison chart of the microwave band absorption curve simulation results and actual test results of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 when the electromagnetic wave is vertically incident. 1 is the simulated microwave absorptivity, and 2 is the tested microwave absorptivity; wherein N≥20 columns and M≥20 rows are set in simulation, and N=20 columns and M=20 rows are set in actual test. The absorption curve of the microwave frequency band 8GHz~18GHz is obtained by testing in a microwave darkroom using the bow method; as can be seen from the figure, the absorption rate is above 90% in the range of 8.9GHz~16.4GHz, and the absorption bandwidth is 59.3%. At the same time, the test results are in good agreement with the simulation results.

[0069] Figure 7 This is a simulation result diagram of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 0°; Figure 8 This is a simulation result diagram of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 15°; Fig. 9 This is a simulation result diagram of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 30°; Fig.10 The figure is a simulation result of the absorption rate of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at an azimuth angle of 45°; wherein the N is set to be ≥ 20 columns and the M is set to be ≥ 20 rows during the simulation. As can be seen from the figure, the optically transparent multi-spectral stealth integrated metamaterial has the excellent characteristic of being polarization insensitive.

[0070] Fig.11 The simulation results of the absorption rate of TE waves of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 at different pitch angles are shown in Figure 1, where 1 is a pitch angle of 0°, 2 is a pitch angle of 15°, 3 is a pitch angle of 30°, and 4 is a pitch angle of 45°; Fig.12The figure is a simulation result of the absorption rate of TM waves at different pitch angles of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1, 1 is a pitch angle of 0°, 2 is a pitch angle of 15°, 3 is a pitch angle of 30°, and 4 is a pitch angle of 45°; wherein N≥20 columns and M≥20 rows are set during simulation. It can be seen from the figure that the optically transparent multi-spectral stealth integrated metamaterial can achieve an absorption rate of more than 80% within the working frequency band at an incident angle of 45° under TE waves and TM waves, respectively, indicating that the metasurface structure has good angular stability.

[0071] The thickness of the middle transparent medium layer of the optically transparent multi-spectral stealth integrated metamaterial prepared in Example 1 is 2 mm, which is equivalent to 0.105 times the lowest frequency wavelength of the working frequency band, indicating that this example has the characteristic of low profile.

Claims

1. An optically transparent multi-spectral stealth integrated metamaterial, characterized in that It is composed of a blank insert patterned impedance film layer, a first transparent substrate, an intermediate transparent medium layer, a second transparent substrate and a second transparent conductive film in order from top to bottom; The blank insert patterned impedance film layer is composed of N×M transparent patterned impedance film units in an array; N is ≥ 20 columns, and M is ≥ 20 rows; the side length of the transparent patterned impedance film unit is P; The transparent patterned impedance film unit is composed of a first transparent conductive film and four groups of blank insert array units. Four groups of blank insert array units are arranged around the center of the transparent patterned impedance film unit; the four groups of blank insert array units are not covered by the first transparent conductive film; The blank insert array unit is composed of three parallel blank inserts, and the parallel blank inserts are parallel to the side of the transparent patterned impedance film unit; assuming that the width of the blank insert is W, the width W of the three parallel blank inserts is 0.05mm~0.25mm, and the vertical distances between the inner side edges of the three parallel blank inserts and the center of the transparent patterned impedance film unit are L1, L2 and L3, respectively, and L1 is 3.2mm~10mm, L2-(L1+W)=1mm~10mm, L3-(L2+W)=1.8mm~10mm, and P-2(L3+W)=1.2mm~10mm; The thickness of the blank insert patterned impedance film layer is 0.01 μm to 3 μm; The thickness of the first transparent substrate and the second transparent substrate are both 0.05mm~2mm; The thickness of the intermediate transparent medium layer is 1 mm to 8 mm; The thickness of the second transparent conductive film is 0.01 μm to 3 μm; The materials of the first transparent conductive film and the second transparent conductive film are aluminum-doped zinc oxide, fluorine-doped tin dioxide or indium tin oxide; The sheet resistance of the first transparent conductive film and the second transparent conductive film is 1Ω / sq~400Ω / sq; The materials of the first transparent substrate and the second transparent substrate are one or a composite of several of polycarbonate, polyvinyl chloride, polydimethylsiloxane and polyethylene terephthalate; The material of the intermediate transparent medium layer is one or a composite of transparent flexible polymer material and transparent flexible inorganic material; the relative dielectric constant of the intermediate transparent medium layer is 1-6; The relative dielectric constants of the first transparent substrate and the second transparent substrate are both 1-6.

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