Microwave-infrared dual-band camouflage metasurface transparent to visible light and preparation method thereof

Abstract

The invention discloses a microwave and infrared dual-band camouflage metasurface transparent to visible light and a preparation method, and belongs to the technical field of electromagnetic metamaterials. The metasurface is formed by sequentially stacking a patterned transparent conductive film, a transparent medium substrate and a continuous transparent conductive film. Wherein all-phase coverage of 0-360 degrees can be achieved through rotation of the anisotropic patterning units, incident electromagnetic waves are scattered to the non-threat direction, and RCS reduction larger than or equal to 10 dB is achieved within the frequency band of 7.9-14.8 GHz; the transparent conductive thin films on the top layer and the bottom layer are AZO / Ag / AZO laminated nano thin films, and the low infrared emissivity smaller than or equal to 0.32 can be achieved in the wave band of 3-14 micrometers. Finally, the camouflage structure synchronously meets the requirements that the visible light transmittance is larger than or equal to 85%, infrared stealth and broadband microwave scattering are reduced, and the complexity limitation of a traditional multi-layer design is broken through. The method is suitable for the electromagnetic protection of military equipment multi-spectrum stealth and civil transparent devices (such as radomes and optical windows).

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic invisibility materials, and particularly relates to a single-layer super surface structure which is transparent in the visible light wave band, realizes wide-band reduction in the microwave wave band, and maintains low emissivity in the infrared wave band, and is suitable for the surfaces of equipment (such as a cockpit cover and a ship observation window) requiring multi-spectrum invisibility. BACKGROUND

[0002] A new type of artificial electromagnetic material, also known as electromagnetic super material, is a kind of artificial material composed of a periodic or quasi-periodic array of sub-wavelength structures. Electromagnetic super material can control the amplitude, phase, polarization state, frequency and even angular momentum of electromagnetic waves, thus attracting widespread attention. Super material has a wide range of applications, such as absorbers, planar lenses and polarization converters.

[0003] In modern society, multi-spectrum camouflage technology is a key technology for improving the concealment of equipment and personnel in different environments. Traditional camouflage technology mainly targets the visible light spectrum, while multi-spectrum camouflage technology covers a wider electromagnetic spectrum, including infrared, microwave, visible light and other light spectra, of which infrared and microwave detection account for 90% of detection methods. The development of this technology is due to the gradual improvement of modern reconnaissance technology, especially in the context of the popularity of advanced sensing equipment and satellite monitoring technology, single-spectrum camouflage has been unable to meet the needs of modern battlefields. Specifically, infrared invisibility requires high reflectivity materials, while microwave invisibility requires low reflectivity materials, and due to the intrinsic properties of natural materials, such materials with unique electromagnetic properties do not exist in nature. Multi-spectrum camouflage performance will be adversely affected.

[0004] Currently, super material has the characteristics of flexible control of electromagnetic waves, which can be adjusted by designing units to adjust electromagnetic response. For example, polarization conversion, by designing a phase unit that can cover 0-360° by rotating, realizing microwave polarization attenuation, at the same time, low infrared emissivity material will make the surface have low infrared emissivity, ensuring the multi-spectrum camouflage performance. SUMMARY

[0005] The purpose of the application is to solve the problem of multi-layer multi-spectrum camouflage material and complex structure, and to provide a super surface with simple structure, high transparency in visible light, wide-band RCS (radar cross section) reduction and low infrared emissivity, which can realize multi-spectrum camouflage effect.

[0006] To achieve the technical purpose, the technical solution adopted by the application is as follows:

[0007] The visible light transparent microwave infrared dual-band camouflage metasurface comprises a patterned transparent conductive film layer, a transparent dielectric substrate layer and a continuous transparent conductive film layer which are sequentially stacked from top to bottom, the patterned transparent conductive film layer is composed of periodically arranged anisotropic structure units, the anisotropic structure units have asymmetric geometric shapes, and the patterned transparent conductive film layer realizes full-range coverage of the reflection phase to regulate microwave scattering through unit rotation; the reflection phase is realized to regulate microwave scattering; the continuous transparent conductive film layer is used to form microwave destructive interference and infrared band high reflection with the patterned transparent conductive film layer.

[0008] To optimize the technical solution, the specific measures taken also include:

[0009] The patterned transparent conductive film layer and the continuous transparent conductive film layer described above are both oxide-metal-oxide laminated structures.

[0010] The oxide is zinc aluminum oxide, the metal is silver, and the laminated configuration is zinc aluminum oxide-silver-zinc aluminum oxide.

[0011] The total thickness of the zinc aluminum oxide-silver-zinc aluminum oxide laminated layer is 100-120nm, wherein: the thickness of the top layer of zinc aluminum oxide is 30-70nm; the thickness of the middle silver layer is 5-12nm; and the thickness of the bottom layer of zinc aluminum oxide is 30-70nm.

[0012] The thickness of the transparent dielectric substrate layer is 2-4mm, and the dielectric constant is 2.2-3.

[0013] The average emissivity of the metasurface in the 3-14μm infrared band is 0.25-0.32, and the radar scattering cross section reduction in the 7.9-14.8GHz frequency band is ≥10dB, the radar scattering cross section reduction is realized by a coded metasurface, the coded metasurface is composed of a plurality of repeated supercell units, each supercell unit contains a preset number of anisotropic structure units, and the rotation angles of at least part of the anisotropic structure units are different.

[0014] The supercell unit is composed of 5x5 anisotropic structure units, and the rotation angles of the anisotropic structure units are arranged in a pseudo-random sequence.

[0015] The preparation method of the visible light transparent microwave infrared dual-band camouflage metasurface comprises the following steps:

[0016] Depositing a zinc aluminum oxide-silver-zinc aluminum oxide laminated layer on the upper surface of the transparent dielectric substrate by magnetron sputtering;

[0017] Forming periodically arranged anisotropic structure units by laser etching the laminated layer, the anisotropic structure units have asymmetric geometric shapes, and the patterned transparent conductive film layer is formed,

[0018] A zinc aluminum oxide-silver-zinc aluminum oxide stack is deposited on the lower surface of the transparent medium substrate by magnetron sputtering to form a continuous transparent conductive film layer.

[0019] The magnetron sputtering parameters are as follows: vacuum degree 5*10 -3 Pa; substrate temperature 150 DEG C; sputtering power 200 W.

[0020] The laser etching parameters are as follows: laser wavelength 355 nm; pulse frequency 20 kHz; scanning speed 500 mm / s.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The present application ingeniously designs anisotropic units and material combinations in a single-layer metasurface structure, simultaneously achieving high transparency in the visible light band, wide-band scattering reduction in the microwave band, and low thermal radiation characteristics in the infrared band, solving the technical problem of requiring multi-layer stacking in traditional multi-spectrum camouflage.

[0023] (2) The present application utilizes a specific arrangement of anisotropic units to achieve intelligent regulation of incident microwaves, significantly reducing the radar scattering characteristics of the target in a wide frequency band through a dual mechanism of phase interference and polarization conversion.

[0024] (3) The present application adopts a specially designed transparent conductive stack structure, which maintains the high light transmission characteristics of the material in the visible light band while ensuring microwave and infrared functions, and is suitable for application scenarios that require visual transparency.

[0025] (4) The present application adopts a single-layer integrated design, avoiding complex multi-layer structures, which not only simplifies the preparation process, but also improves the environmental adaptability and reliability of the product, especially suitable for practical applications in complex environments.

[0026] (5) The present application solves the technical contradiction between microwave absorption and infrared reflection, optical transparency and electromagnetic regulation through innovative structural design, achieving the synergistic optimization of multiple functions. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a top view of the metasurface of the present application with a single anisotropic structural unit;

[0028] Figure 2 is a side view of the metasurface of the present application with a single anisotropic structural unit;

[0029] Figure 3 is a reflection phase diagram of the metasurface of the present application in mode 0 and mode 1;

[0030] Figure 4 is a vector calculation result diagram of the reflection coefficient of the present application;

[0031] Figure 5 Arrangement of the overall structure of the application;

[0032] Figure 6 3D far-field scattering characteristic diagram of the application. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is described and explained below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. Based on the examples provided in the present application, all other examples obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0034] Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those of ordinary skill in the art, the present application can also be applied to other similar scenarios without creative labor on the basis of these drawings. In addition, it can be understood that although the efforts made in this development process can be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacture or production changes based on the technical content disclosed in the present application are only routine technical means and should not be understood as insufficient disclosure of the present application.

[0035] As Figures 1-2 shown, the embodiment of the present application discloses a visible light transparent microwave infrared dual-band camouflage metasurface. The basic unit of the metasurface includes a patterned transparent conductive film layer, a transparent dielectric substrate layer and a continuous transparent conductive film layer arranged in sequence, the patterned transparent conductive film layer is composed of periodically arranged anisotropic structure units, the anisotropic structure units have asymmetric geometric shapes, when the metasurface is prepared, the anisotropic units are permanently fixed on the patterned transparent conductive film layer at a preset rotation angle (such as 0°, 90°, 45°, etc.) by laser etching, thereby realizing unit rotation. The patterned transparent conductive film layer, the transparent dielectric substrate layer and the continuous transparent conductive film layer form a microwave low reflection metasurface, which also has low infrared emissivity. Since transparent materials are used, the metasurface has high light transmittance.

[0036] The preparation of a single-layer metasurface includes the following steps:

[0037] Depositing an AZO (50 nm) / Ag (10 nm) / AZO (50 nm) stack on the front surface of the PMMA substrate by magnetron sputtering;

[0038] Further, the sputtering process parameters are: vacuum degree 5x10 -3Pa, substrate temperature 150℃, sputtering power 200W;

[0039] Laser etching top layer AZO / Ag / AZO to form a patterned structure;

[0040] Further, etching parameters: laser wavelength 355nm, pulse frequency 20kHz, scanning speed 500mm / s;

[0041] Continuous AZO / Ag / AZO film layer is attached to the back of the PMMA substrate.

[0042] Microwave scattering characteristics of single-layer metasurface: RCS reduction >10dB in the 7.9-14.8GHz band;

[0043] Further, the maximum reduction at 13.2GHz is 18.7dB;

[0044] Infrared stealth characteristics: Fourier infrared spectrometer measured average emissivity of 0.29 in the 3-14micron band.

[0045] Figure 1 and 2 The top view and side view of the metasurface with a single anisotropic structure unit are shown, where the labeled structure parameters are: l1=7.6mm, l2=5mm, l3=3.6mm, d=1mm, g=0.6mm, P=8mm, h=3mm. Under this structure parameter, the infrared emissivity of the metasurface is 0.29 respectively. Figure 1 u and v in the formula represent the direction of electric field polarization, specifically, mode 0 when the electric field is polarized along the u direction, and mode 1 when the electric field is polarized along the v direction.

[0046] Figure 3 The reflection phase of the metasurface in mode 0 and mode 1 is shown, and there is a certain phase difference between the two polarization modes, which can bring a certain RCS reduction.

[0047] Figure 4 It is the vector calculation result of the reflection coefficient of the present application, and the polarization conversion rate is greater than 0.9. As can be seen from the figure, the present application has an RCS reduction of-10dB in the 7.9-14.8GHz band.

[0048] Figure 5 The arrangement mode of the overall structure of the present application is shown.

[0049] Figure 6 Under the condition of normal incidence, the 3D far-field scattering characteristics of the pseudo-random coded metasurface and the equal-size metal plate at 8.4GHz, 10.3GHz and 13.2GHz are simulated and compared. It can be seen that compared with the equal-size metal plate, the present application can significantly reduce the RCS characteristics of the target.

[0050] The embodiments described are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A visible-light transparent microwave-infrared dual-band camouflage metasurface, characterized in that, It includes a patterned transparent conductive film layer, a transparent dielectric substrate layer and a continuous transparent conductive film layer stacked from top to bottom. The patterned transparent conductive film layer is composed of periodically arranged anisotropic structural units. The anisotropic structural units have asymmetrical geometry. The patterned transparent conductive film layer achieves full coverage of the reflection phase by rotating the units to control microwave scattering. The continuous transparent conductive film layer is used in conjunction with the patterned transparent conductive film layer to form microwave phase interference cancellation involving high reflectivity in the infrared band.

2. The visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 1, characterized in that, Both the patterned transparent conductive thin film layer and the continuous transparent conductive thin film layer are oxide-metal-oxide stacked structures.

3. The visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 2, characterized in that, The oxide is zinc aluminum oxide, the metal is silver, and the stacked configuration is zinc aluminum oxide-silver-zinc aluminum oxide.

4. The visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 3, characterized in that, The total thickness of the zinc oxide-silver-zinc oxide-aluminum oxide stack is 100-120nm, of which: the thickness of the top zinc oxide layer is 30-70nm; the thickness of the middle silver layer is 5-12nm; and the thickness of the bottom zinc oxide layer is 30-70nm.

5. A visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 3, characterized in that, The thickness of the transparent dielectric substrate layer is 2-4 mm, and the dielectric constant is 2.2-3.

6. A visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 1, characterized in that, The metasurface has an average emissivity of 0.25-0.32 in the 3-14μm infrared band and a radar cross section reduction of ≥10dB in the 7.9-14.8GHz frequency band. The radar cross section reduction is achieved by a coded metasurface, which is composed of multiple repeating supercell units. Each supercell unit contains a predetermined number of anisotropic structural units, and at least some of the anisotropic structural units have different rotation angles.

7. A visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 6, characterized in that, The supercell unit is composed of 5×5 anisotropic structural units, and the rotation angles of the anisotropic structural units are arranged in a pseudo-random sequence.

8. The method for preparing a visible-light transparent microwave-infrared dual-band camouflage metasurface as described in any one of claims 1-7, characterized in that, Includes the following steps: A zinc oxide-silver-zinc oxide-aluminum oxide stack was deposited on the surface of a transparent dielectric substrate by magnetron sputtering. The stacked layers are etched using laser etching to form periodically arranged anisotropic structural units with asymmetrical geometric shapes, forming a patterned transparent conductive thin film layer. A continuous transparent conductive thin film layer is formed by depositing a zinc oxide-silver-zinc oxide-aluminum oxide stack on the lower surface of a transparent dielectric substrate via magnetron sputtering.

9. The method for preparing a visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 8, characterized in that, The magnetron sputtering parameters are: vacuum degree 5×10 -3 Pa; substrate temperature 150℃; sputtering power 200W.

10. The method for preparing a visible-light transparent microwave-infrared dual-band camouflage metasurface according to claim 8, characterized in that, The laser etching parameters are: laser wavelength 355nm; pulse frequency 20kHz; scanning speed 500mm / s.

Images