Metamaterial-based optical transparent bidirectional wave-absorbing glass as well as preparation method and application thereof

Abstract

The invention discloses metamaterial-based optical transparent bidirectional wave-absorbing glass as well as a preparation method and application thereof. The transparent bidirectional wave-absorbing glass is of a multi-layer gradient structure constructed by an optical transparent glass layer and a transparent conductive film metamaterial layer, wherein the transparent conductive film metamaterial layer is carved on the surface of the optical transparent glass, and the optical transparent glass is connected through an organic film. According to the invention, the multilayer gradient symmetrical structure is designed, the transparent and wave-absorbing carrier functions are considered, and high optical transparency and high bidirectional wave-absorbing are realized at the same time.

Description

Technical Field

[0001] This invention belongs to the field of optically transparent and radar absorbing material preparation technology, and relates to a metamaterial-based optically transparent bidirectional absorbing glass, its preparation method and application. Background Technology

[0002] Traditional stealth materials (radar-absorbing materials) and novel artificial electromagnetic stealth materials, after long-term development, can now meet the vast majority of military and civilian needs, powerfully driving technological progress in related fields. However, due to limitations imposed by the physical properties of their constituent materials, existing stealth materials often lack optical transparency, making them unsuitable for certain special applications, such as aircraft cockpit windows and building doors and windows, where user visual perception must also be considered. This restricts the development of related fields.

[0003] Currently, existing transparent absorbing materials mainly use ordinary optical glass as a substrate. However, ordinary optical glass itself is a wave-transmitting material and does not possess wave-absorbing properties. Special absorbing structures need to be constructed on its surface to achieve transparent wave absorption. This approach has several drawbacks, such as increasing the complexity and cost of material preparation. Furthermore, the construction of special structures hinders further improvements and breakthroughs in the wave-absorbing performance of transparent optical windows, making it difficult to simultaneously meet the requirements of high optical transparency and high microwave absorption. In addition, traditional absorbers can only absorb forward-incident electromagnetic waves, while reverse electromagnetic waves are completely reflected. This reduces the overall utilization rate of electromagnetic energy and suffers from the drawback of being untunable, failing to meet the needs of next-generation intelligent and integrated wave-absorbing optical windows.

[0004] Especially in the military field, current transparent windows with electromagnetic functional requirements generally employ a transparent, highly conductive metal / semiconductor thin film deposited on the surface of substrates such as glass, combined with an overall shape design. This achieves electromagnetic shielding while simultaneously redirecting radar echoes towards areas with lower detection threats through the film and shape reflection, thus achieving stealth capabilities. However, stealth for ship and vehicle windows is difficult to achieve solely through shape design, and shape-based stealth technology does not reduce the total energy of the echo. With the development of detection technology, reflective stealth technology relying solely on shape is insufficient to achieve good stealth effects. The stealth of transparent windows is evolving from reflective to absorptive. For currently widely used transparent conductive materials, their transmittance and conductivity exhibit an antagonistic relationship, making it difficult for transparent windows to simultaneously achieve high optical transmittance and strong radar absorption stealth performance. Metamaterial optically transparent absorbing materials based on transparent conductive thin films can effectively compensate for the shortcomings of the aforementioned technologies. However, the preparation of materials that simultaneously possess optical transparency and radar absorption remains a significant technical challenge in this field. Summary of the Invention

[0005] In view of this, the main objective of this invention is to provide a metamaterial-based optically transparent bidirectional absorbing glass, its preparation method, and its application. The technical problem to be solved is how to make the prepared transparent bidirectional absorbing glass have a transmittance of ≥72% in the visible light band, an absorption rate of ≥85% for bidirectional incident electromagnetic waves in the 5~40 GHz frequency range, and an absorption rate of ≥90% in some frequency bands, so as to adapt to the needs of scenarios that need to take into account both vision and stealth, realize bidirectional absorption stealth of transparent windows, and meet the requirements of intelligence and integration.

[0006] The objective of this invention and the technical problem it solves are achieved by the following technical solution. This invention proposes a metamaterial-based optically transparent bidirectional absorbing glass, wherein the transparent bidirectional absorbing glass is a multi-layered gradient structure constructed from an optically transparent glass layer and a transparent conductive thin-film metamaterial layer; wherein the transparent conductive thin-film metamaterial layer is etched on the surface of the optically transparent glass layer, and the optically transparent glass layer is connected by an organic film.

[0007] The objectives of this invention and the technical problems solved can be further achieved by the following technical measures.

[0008] Preferably, in the aforementioned metamaterial-based optically transparent bidirectional absorbing glass, the transparent conductive thin film metamaterial layer is a structural unit consisting of a combination of windmill-shaped, square, and ring-shaped layers.

[0009] Preferably, the aforementioned metamaterial-based optically transparent bidirectional absorbing glass includes, from the surface to the core, a first transparent glass layer, a first metamaterial stacking unit, a second metamaterial stacking unit, a second transparent glass layer, a conductive transparent film, a third transparent glass layer, a third metamaterial structural unit, a fourth metamaterial stacking unit, and a fourth transparent glass layer.

[0010] Preferably, in the aforementioned metamaterial-based optically transparent bidirectional absorbing glass, the thickness of the first, second, third, and fourth transparent glass layers is 1 to 3 mm.

[0011] Preferably, in the aforementioned metamaterial-based optically transparent bidirectional absorbing glass, the side length of the first, second, third, and fourth metamaterial stacking units is 8 to 16 mm.

[0012] Preferably, in the aforementioned metamaterial-based optically transparent bidirectional absorbing glass, the thickness of the first, second, third, and fourth metamaterial stacking units is 0.5~4 mm.

[0013] Preferably, in the aforementioned metamaterial-based optically transparent bidirectional absorbing glass, the transparent conductive film is made of aluminum-doped zinc oxide, fluorine-doped arsenic dioxide, or indium tin oxide, and the thickness of the transparent conductive film is 85~150 nm.

[0014] Preferably, the aforementioned metamaterial-based optically transparent bidirectional absorbing glass has an absorption rate of over 85% in the frequency range of 5 to 40 GHz.

[0015] The objectives of this invention and the technical problems it solves can be further achieved by the following technical measures. This invention proposes a method for preparing a metamaterial-based optically transparent bidirectional absorbing glass, comprising the following steps: thermomagnetron sputtering to deposit a transparent conductive thin film, laser etching of a metamaterial pattern, and then hot-pressing to bond the glass and an organic film, thereby obtaining the metamaterial-based optically transparent bidirectional absorbing glass.

[0016] The objectives of this invention and the technical problems solved can be further achieved by the following technical measures.

[0017] Preferably, in the aforementioned method for preparing metamaterial-based optically transparent bidirectional absorbing glass, the parameters of the thermomagnetron sputtering are set as follows: argon flow rate of 18~30 sccm, target sputtering power of 80~150 W, and substrate temperature of 60~120℃.

[0018] Preferably, in the aforementioned method for preparing metamaterial-based optically transparent bidirectional absorbing glass, the laser etching parameters are set as follows: laser wavelength is 355~1064 nm, power is 10~30 W, and scanning speed is 100~500 mm / s.

[0019] Preferably, in the aforementioned method for preparing metamaterial-based optically transparent bidirectional absorbing glass, the hot-pressing parameters are set as follows: temperature 120~160 ℃, pressure 0.5~1.2 MPa, and hot-pressing time 15~30 min.

[0020] The objectives of this invention and the solutions to its technical problems can also be achieved using the following technical measures. This invention proposes a transparent absorbing glass, wherein the transparent absorbing glass adopts the aforementioned metamaterial-based optically transparent bidirectional absorbing glass; the transparent absorbing glass includes an electromagnetic wave transmission channel, a metamaterial carrier, and an electromagnetic wave absorption layer, wherein the electromagnetic wave transmission channel and the metamaterial carrier are optically transparent glass layers; and the electromagnetic wave absorption layer is a transparent conductive thin-film metamaterial layer.

[0021] The objectives of this invention and the solutions to its technical problems can also be achieved using the following technical measures. This invention proposes an architectural glass, wherein the architectural glass is made of the aforementioned metamaterial-based optically transparent bidirectional absorbing glass.

[0022] The objectives of this invention and the solutions to its technical problems can also be achieved using the following technical measures. This invention proposes a transparent window, characterized in that the transparent window uses the aforementioned metamaterial-based optically transparent bidirectional absorbing glass, and the transparent window includes any one of aircraft cockpit glass, ship and vehicle viewing windows, UAV optical reconnaissance windows, and high-speed train driver's cab windows.

[0023] Compared with existing technologies, the metamaterial-based optically transparent bidirectional absorbing glass, its preparation method, and its applications described in this invention have the following beneficial effects: Balancing High Optical Transparency and High Microwave Absorption Performance: This invention combines transparent glass, metamaterial stacking units, and a transparent conductive film to achieve high transmittance (over 72%) in the visible light band, while exhibiting excellent absorption performance for bidirectional incident electromagnetic waves in the microwave band (5-40 GHz), with an absorption rate greater than or equal to 85%, and exceeding 90% in some frequency bands. The transparent glass itself has excellent transmittance in the visible light band, and the metamaterial stacking units are made of dielectric materials with low visible light loss. Furthermore, the unit structure size is much smaller than the visible light wavelength, so it does not significantly hinder visible light propagation, ensuring high transmittance. The periodic structure of the metamaterial stacking units can resonate with electromagnetic waves in the microwave band, while the transparent conductive film can further dissipate microwave energy. The synergistic effect of these two components enables the glass to achieve efficient absorption in the microwave band, effectively solving the problem that existing transparent absorbing materials cannot simultaneously meet the requirements of high optical transparency and high microwave absorption.

[0024] Bidirectional microwave absorption: The metamaterial layer adopts a symmetrical periodic structure design, which has the same response characteristics to microwave electromagnetic waves incident in both directions and can equally excite the resonance effect; at the same time, the transparent conductive film is uniformly covered on both sides of the metamaterial layer, which can produce a consistent energy loss effect on the incident microwaves in both directions, thereby realizing bidirectional microwave absorption; providing a more effective solution for applications in complex electromagnetic environments.

[0025] Simple structure and easy preparation method: The metamaterial-based optically transparent bidirectional absorbing glass structure of the present invention is reasonably designed, the materials of each layer are common and easy to obtain, and the preparation process adopts conventional photolithography, etching, spin coating and curing processes, which are simple to operate, easy to realize large-scale production, and reduce production costs.

[0026] Broad application prospects: The metamaterial-based optically transparent bidirectional absorbing glass of the present invention has potential application value in multiple fields such as electromagnetic stealth and wireless communication. It can meet the needs for optical transparency and electromagnetic protection in different scenarios, provide new material options for the technological development of related fields, and is expected to be widely used in industry.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Attached Figure Description

[0028] Figure 1 This is a cross-sectional schematic diagram of a metamaterial-based optically transparent bidirectional absorbing glass prepared according to some embodiments of the present invention; Figure 2 This is a schematic diagram of the windmill-shaped metamaterial structural unit in Embodiment 2 of the present invention; Figure 3 The energy loss density diagram is shown for the metamaterial-based optically transparent bidirectional absorbing glass prepared in Example 2 of this invention. Figure 4 This is a macroscopic image of the metamaterial-based optically transparent bidirectional absorbing glass prepared in Example 3 of the present invention; Figure 5A This is one of the schematic diagrams of the superimposed metamaterial structural units in the windmill-shaped, square, and ring-shaped combination in Embodiment 4 of the present invention; Figure 5B This is a second schematic diagram of the superimposed metamaterial structural unit consisting of windmill-shaped, square, and ring-shaped elements in Embodiment 4 of the present invention. Figure 6 The image shows the absorption curve of the metamaterial-based optically transparent bidirectional absorbing glass prepared in Example 4 of this invention. Wherein, 1-first transparent glass layer; 2-first organic film; 3-second transparent glass layer; 4-third transparent glass layer; 5-second organic film; 6-fourth transparent glass layer; 7-first metamaterial structural unit; 8-second metamaterial structural unit; 9-conductive transparent film; 10-third metamaterial structural unit; 11-fourth metamaterial structural unit; 13-windmill shape; 14-square; 15-ring shape; a-0.8mm; b-0.8mm; c-0.8mm; d-3.2mm; e-1.2mm; f-4.8mm; x-10mm. Detailed Implementation

[0029] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following detailed description, in conjunction with preferred embodiments, details a metamaterial-based optically transparent bidirectional absorbing glass, its preparation method, and its application, including its specific implementation, structure, features, and effects. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0030] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well-known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art. Where specific experimental steps or conditions are not specified below, they can be performed according to the conventional experimental steps or conditions described in the literature in this field.

[0031] like Figure 1 As shown, according to some embodiments of the present invention, a metamaterial-based optically transparent bidirectional absorbing glass is provided. The transparent bidirectional absorbing glass is a multi-layered gradient structure constructed from an optically transparent glass layer and a transparent conductive thin film metamaterial layer. The transparent conductive thin film metamaterial layer is directly etched on the surface of the optically transparent glass layer, and the optically transparent glass layer is connected by an organic film.

[0032] To meet the core requirements of "transparency" and "bidirectional wave absorption" and adapt to practical application scenarios, this metamaterial-based optically transparent bidirectional wave-absorbing glass adopts a multi-layer gradient structure design: the optically transparent glass serves as a rigid substrate, ensuring high visible light transmittance to achieve the glass's transparency function, while also providing physical support and a stable processing carrier for the ultra-thin and fragile transparent conductive film metamaterial layer; the transparent conductive film metamaterial layer, by engraving specific micro-periodic structures (with periods much smaller than the wavelength of visible light) on the glass surface, can resonate with specific frequency band electromagnetic waves incident bidirectionally and dissipate their energy, achieving bidirectional wave absorption without affecting transparency (avoiding electromagnetic interference and information leakage); the organic film can achieve high-strength bonding of the multi-layer glass through heating and pressurization, making the overall structure integrated to improve impact resistance. At the same time, its refractive index is close to that of glass, which can reduce interlayer light reflection, improve light transmission uniformity, and also encapsulate the metamaterial layer to isolate water vapor and oxygen erosion to ensure long-term stability. Ultimately, it achieves a balance of multiple performances including transparency, wave absorption, safety, and durability, making it suitable for architectural, automotive, and other application scenarios.

[0033] In some optional embodiments, the transparent conductive thin-film metamaterial layer can be a combination of at least two of the following structural units: windmill-shaped, square, and ring-shaped. This arrangement allows the metamaterial layer to cover a wide frequency range from microwaves to millimeter waves by complementing the frequency bands of at least two of the windmill-shaped, square, and ring-shaped structures, avoiding the limitations of single-band narrow-frequency absorption. At least two of the windmill-shaped, square, and ring-shaped structures can achieve "efficient electromagnetic wave capture + efficient heat dissipation," improving overall absorption efficiency. Furthermore, because all three structures are hollow or dispersed microscopic morphologies with low structural duty cycles and do not obstruct visible light transmission, they can maintain the high optical transparency of the glass while ensuring absorption functionality, adapting to visual requirements.

[0034] In some optional embodiments, the transparent bidirectional absorbing glass may include a first transparent glass layer 1, a first metamaterial stacking unit 7, a second metamaterial stacking unit 8, a second transparent glass layer 3, a conductive transparent film 9, a third transparent glass layer 4, a third metamaterial structural unit 10, a fourth metamaterial structural unit 11, and a fourth transparent glass layer 6 arranged sequentially from the surface to the core. The first transparent glass layer 1 and the second transparent glass layer 3 are connected by a first organic film 2; the first metamaterial stacking unit 7 and the second metamaterial stacking unit 8 are connected by the first organic film 2; the third transparent glass layer 4 and the fourth transparent glass layer 6 are connected by a second organic film 5; the third metamaterial structural unit 10 and the fourth metamaterial structural unit 11 are connected by a second organic film 5. This arrangement, by alternately embedding metamaterial stacking units and conductive transparent films between the multiple transparent glass layers, allows the metamaterial units to form a multi-dimensional wave-absorbing structure from the glass surface to the core, enabling multiple capture and dissipation of electromagnetic waves incident from different directions. Simultaneously, the conductive transparent film helps adjust the overall electromagnetic parameters, further improving absorption efficiency and broadband coverage. Furthermore, the transparent materials of each layer work together to ensure visible light transmittance, balancing wave absorption, structural safety, and optical transparency. The refractive index of the organic film is close to that of the optically transparent glass, used to achieve high-strength bonding of the multiple glass layers and reduce interlayer light reflection.

[0035] In some optional embodiments, the side lengths of the first, second, third, and fourth metamaterial stacking units can all be set to 8-16 mm. If the side lengths of the first, second, third, and fourth metamaterial stacking units are less than 8 mm, the resonant coupling ability with the target absorption frequency band (such as microwaves and millimeter waves) will be weakened due to the small structural size, resulting in a significant decrease in absorption efficiency. Moreover, the small size makes it difficult to ensure structural accuracy in micro-nano fabrication, easily leading to process errors. If the side lengths are greater than 16 mm, not only will the structural size exceed the visible light wavelength adaptation range, resulting in a significant reduction in glass transmittance (with visible structural shadows), but the unit spacing will also be mismatched with the electromagnetic wave wavelength, causing absorption frequency band breaks and making it impossible to achieve broadband coverage. Setting the side lengths to 8-16 mm ensures efficient resonance between the metamaterial units and the target absorption frequency band electromagnetic waves to guarantee absorption performance, avoids the influence of the structure on visible light transmission, adapts to the accuracy of existing micro-nano fabrication processes, and balances functionality, optical effects, and production feasibility.

[0036] In some optional embodiments, the thickness of the first, second, third, and fourth transparent glass layers is 1-3 mm, and the thickness of the first, second, third, and fourth metamaterial stacking units is 0.5-4 mm. A thickness of less than 1 mm for the optically transparent glass layers results in insufficient mechanical strength, making them prone to breakage, difficult to support the metamaterial units, and weak protection; a thickness greater than 3 mm increases weight and cost, and reduces light transmittance. A thickness of less than 0.5 mm for the metamaterial stacking units leads to poor conductivity, causing a sharp drop in absorption efficiency and making them prone to breakage; a thickness greater than 4 mm results in superimposed light reflection and scattering, reduced light transmittance, and increased difficulty in interlayer bonding. Setting the thickness of the optically transparent glass layers to 1-3 mm balances mechanical support, light transmittance, and cost; setting the thickness of the metamaterial stacking units to 0.5-4 mm ensures absorption efficiency and structural stability, ultimately achieving the comprehensive performance of glass that is "wave-absorbing, transparent, and durable."

[0037] In some optional embodiments, the transparent conductive film can be made of aluminum-doped zinc oxide (AZO), fluorine-doped arsenic dioxide (FTO), or indium tin oxide (ITO), with a thickness of 85-150 nm. The core reason for choosing AZO, FTO, or ITO as the transparent conductive film is that they possess both high visible light transmittance (typically ≥85%) and excellent conductivity. This allows them to provide a stable conductive substrate for the metamaterial unit to achieve electromagnetic resonance absorption while ensuring the transparency of the glass. Furthermore, all three have strong chemical stability and can withstand long-term environmental corrosion (such as moisture and oxidation). In addition, AZO does not contain the scarce element indium and is lower in cost; FTO is heat-resistant and suitable for high-temperature processing scenarios; and ITO has the best conductivity and is suitable for high absorption efficiency requirements. The three materials can be selected as needed, balancing functionality, stability, and economic efficiency or process adaptability for different scenarios. If the thickness is less than 85 μm, the discontinuous distribution of conductive particles will lead to insufficient conductivity and increased resistance. At the same time, the thin film is weak and easily damaged, and the light transmission uniformity is poor, which will also reduce the yield of mass production. If the thickness is greater than 150 μm, the light transmittance will decrease significantly due to the enhanced light absorption and scattering. The marginal benefit of improving conductivity will decrease and material waste will occur. At the same time, the film's flexibility will decrease and its brittleness will increase. This will not only be detrimental to the processing, assembly and bonding accuracy, but will also increase the weight and volume of the device, affecting the miniaturization adaptation requirements.

[0038] In some optional embodiments, the metamaterial-based optically transparent bidirectional absorbing glass resonates with microwave electromagnetic waves through the periodic structure of the metamaterial stacking unit, and combined with the energy loss effect of the transparent conductive film, to achieve bidirectional wave absorption function in the frequency range of 5~40 GHz with an absorption rate of more than 85%.

[0039] Some embodiments of the present invention also provide a method for preparing metamaterial-based optically transparent bidirectional absorbing glass, comprising the following steps: S1: A transparent conductive thin film is deposited on optically transparent glass by magnetron sputtering. The operating parameters are as follows: argon pressure 0.3-0.8 Pa, target sputtering power 80-150 W, and substrate temperature 60-120℃. Below 0.3 Pa, insufficient gas pressure leads to low sputtered particle density, slow film deposition rate, poor film density, and decreased conductivity and adhesion. Below 80 W, the power is too low to fully excite the target particles, resulting in poor film uniformity. Below 60℃, the substrate temperature is too low and stress cracking is likely to occur. Above 0.8 Pa, excessive gas pressure increases particle collision loss and reduces film transmittance. Above 150 W, excessive power causes target overheating and evaporation, resulting in uneven film thickness and easy oxidation. Above 120℃, excessive substrate temperature will damage the substrate performance and affect the bonding stability between the film and the substrate. This setting is mainly to balance the deposition rate, film density, and the synergy of light transmittance and conductivity, ensuring that the overall performance of the film is suitable for subsequent etching processes.

[0040] S2: Laser etching of metamaterial patterns on the glass surface coated with an AZO thin film to form a transparent conductive thin-film metamaterial layer. The operating parameters are as follows: laser wavelength 355-1064 nm, power 10-30 W, and scanning speed 100-500 mm / s. Below 355 nm, the wavelength is too long, resulting in insufficient etching resolution and blurred pattern edges; below 10 W, the power is too low to completely remove the film, and residual impurities affect the metamaterial performance; below 100 mm / s, the scanning speed is too slow and can easily cause local overheating and damage to the substrate. Above 1064 nm, the wavelength is too short and can easily cause secondary deposition of the film, reducing pattern accuracy; above 30 W, the power is too high and can ablate the substrate, damaging the glass's light transmittance; above 500 mm / s, the scanning speed is too fast, resulting in incomplete etching and poor pattern integrity. This setting can balance pattern accuracy, edge quality, and etching efficiency, avoid substrate damage, and ensure the integrity of the metamaterial's microwave absorbing structure.

[0041] S3: The glass with the etched metamaterial pattern is bonded to another identical optically transparent glass via hot pressing to create a metamaterial-based optically transparent bidirectional absorbing glass. The operating parameters are as follows: temperature 120-160 ℃, pressure 0.5-1.2 MPa, and hot pressing time 15-30 min. Below 120 ℃, the organic film will not melt sufficiently, resulting in ineffective bonding and insufficient bond strength. Below 0.5 MPa, the pressure will be too low, easily leaving air bubbles and affecting the glass's light transmittance and structural stability. Below 15 min, the bonding reaction will be incomplete, easily leading to delamination. Above 160 ℃, the temperature will be too high, causing the organic film to degrade and age, producing an odor and reducing light transmittance. Above 1.2 MPa, the pressure may crack the glass or cause the film to overflow. Above 30 min, the time will be too long, reducing production efficiency and potentially causing excessive cross-linking and brittleness of the film. This design is intended to adapt to the melting characteristics of organic film, ensure full wetting and bonding at the interface, eliminate air bubble residue, and balance bonding strength and production efficiency.

[0042] Magnetron sputtering is used to deposit transparent conductive films because it can form a uniform, dense, and strongly bonded film layer on the glass surface, ensuring high visible light transmittance and stable conductivity. It is also compatible with various materials such as AZO and ITO, meeting the conductive substrate requirements of metamaterial units. Laser etching of metamaterial patterns is chosen because of its high etching precision (down to the micrometer or even nanometer level), which can accurately reproduce complex superimposed structures such as windmills and squares. Moreover, the etching process causes minimal damage to the film, avoiding damage to transparent conductivity and ensuring the integrity and consistency of the microwave absorption structure. Hot pressing is used to bond the glass and organic film because hot pressing can fully melt the organic film and fill the interlayer gaps, achieving high-strength bonding of multilayer structures. At the same time, it can eliminate interlayer air and reduce light reflection, balancing structural stability and optical transparency. Furthermore, this process is mature, controllable, and suitable for large-scale production.

[0043] Other embodiments of the present invention also provide a transparent absorbing glass, wherein the transparent absorbing glass adopts the above-mentioned metamaterial-based optically transparent bidirectional absorbing glass.

[0044] Furthermore, the transparent absorbing glass includes an electromagnetic wave transmission channel, a metamaterial carrier, and an electromagnetic wave absorption layer. The electromagnetic wave transmission channel and the metamaterial carrier are optically transparent glass layers; the electromagnetic wave absorption layer is a transparent conductive thin film metamaterial layer; and electromagnetic waves are continuously absorbed in the symmetrical layered structure formed by the metamaterial-based optically transparent bidirectional absorbing glass.

[0045] Furthermore, the visible light transmittance of the transparent absorbing glass can reach 72%~78%, which can meet the requirements for clear visual observation and has no obvious structural shadows.

[0046] Furthermore, the transparent absorbing glass has an absorption rate of over 85% in the 5-40 GHz frequency range, and can reach over 90% in some frequency bands (such as 5-15 GHz), which can efficiently dissipate the energy of bidirectional incident microwaves and millimeter waves.

[0047] Furthermore, the thickness of the optically transparent glass layer is 1~3 mm, the thickness of the metamaterial stacking unit is 0.5~4 mm, and the side length is 8~16 mm. The overall structure takes into account both mechanical strength and functional adaptability.

[0048] Furthermore, the transparent conductive film of the transparent absorbing glass is made of aluminum-doped zinc oxide, fluorine-doped arsenic dioxide, or indium tin oxide, which has both high light transmittance and conductivity, and strong chemical stability.

[0049] The transparent radar-absorbing glass can be applied to transparent windows such as aircraft cockpit windows and ship and vehicle windows to achieve absorption-type stealth, avoid radar echoes from exposing the target, and solve the problem of poor performance of traditional reflection-type stealth.

[0050] Other embodiments of the present invention also provide an architectural glass, wherein the architectural glass adopts the above-mentioned metamaterial-based optically transparent bidirectional absorbing glass; the transparent absorbing glass can be used as architectural door and window glass, which can absorb external electromagnetic interference signals, ensure the normal operation of indoor electronic equipment, and at the same time isolate indoor electromagnetic radiation leakage, creating a safe electromagnetic environment.

[0051] Other embodiments of the present invention also provide a transparent window, which adopts the above-mentioned metamaterial-based optically transparent bidirectional absorbing glass. The transparent window includes any one of aircraft cockpit glass, ship and vehicle windows, UAV optical reconnaissance windows, and high-speed train driver's cab windows. The transparent absorbing glass can be used as a transparent partition in communication base station equipment rooms and precision instrument laboratories, which can maintain visual transparency while efficiently shielding electromagnetic waves of specific frequency bands, ensuring the stability of equipment operation. The transparent absorbing glass can be adapted to the windows of high-speed trains and new energy vehicles, absorbing various electromagnetic interferences during driving, improving the anti-interference capability of on-board electronic systems, and ensuring driving safety.

[0052] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0053] Example 1 This embodiment provides a method for preparing metamaterial-based optically transparent bidirectional absorbing glass, including the following steps: Step 1: Select an optically transparent glass (specifically silicate glass) with a thickness of 1 mm, using aluminum-doped zinc oxide (AZO) as the transparent conductive material. Deposit an AZO thin film on the surface of the optically transparent glass using thermomagnetron sputtering. The thermomagnetron sputtering uses an AZO target doped with 2 wt% Al₂O₃, introduces 99.999% pure argon gas at a flow rate of 20 sccm, and sets the sputtering power to 150 W, ultimately forming a 100 nm thick AZO thin film.

[0054] Step 2: Using laser etching technology, windmill-shaped and ring-shaped superimposed metamaterial structural units are etched on the glass surface coated with AZO thin film. The side length of the metamaterial structural unit is 8 mm. The laser etching uses a laser with a wavelength of 1064 nm, an etching speed of 50 mm / s, and a spot diameter of 50 μm to accurately etch the windmill-shaped and ring-shaped superimposed structure with a side length of 9 mm.

[0055] Step 3: The glass with the metamaterial pattern etched in Step 2 is hot-pressed with another identical optically transparent glass (1 mm thick) using a 0.5 mm thick organic film (commercially available). The hot-pressing conditions are: temperature 50 ℃, pressure 0.5 MPa, time 10 min. The above steps are repeated. Finally, a first transparent glass layer, a first metamaterial stacking unit (windmill-shaped and ring-shaped stacked structure), a second transparent glass layer, a transparent conductive film, a third transparent glass layer, a second metamaterial stacking unit (windmill-shaped and ring-shaped stacked structure), and a fourth transparent glass layer are prepared from top to bottom. During hot pressing, PVB organic film is used, and the temperature is maintained at 50 ℃ and the pressure at 0.5 MPa for 10 min. At the same time, nitrogen gas (purity 99.999%) with a flow rate of 40 sccm is introduced to avoid the generation of bubbles. The resulting metamaterial-based optically transparent bidirectional absorbing glass has an optically transparent glass layer thickness of 1 mm and a metamaterial stacking unit thickness of 0.5 mm.

[0056] The application scenario of the metamaterial-based optically transparent bidirectional absorbing glass is the windshield radar window of civilian vehicles. Its absorbing frequency band of 5~15 GHz is suitable for the needs of vehicle radar. The 1 mm thick thin glass combined with 0.5 mm film makes the overall thickness only 3.1 mm, which meets the requirements of lightweighting. Moreover, the AZO material has low cost and is suitable for large-scale application by car companies.

[0057] Tests showed that the glass has an absorption rate of up to 90% in the frequency range of 5 to 15 GHz and an average transmittance of 75% in the visible light band.

[0058] Example 2 This embodiment provides a method for preparing metamaterial-based optically transparent bidirectional absorbing glass, including the following steps: Step 1: Select a 2 mm thick optically transparent glass (specifically silicate glass), and use fluorine-doped arsenic dioxide (FTO) as the transparent conductive material. Deposit an FTO thin film on the glass surface using thermomagnetron sputtering. The thermomagnetron sputtering uses an FTO target doped with 5 wt% F, and introduces a mixture of argon (99.999% purity) and oxygen in a 95:5 volume ratio with a total flow rate controlled at 25 sccm. The sputtering power is set to 200 W, ultimately forming a 120 nm thick FTO thin film.

[0059] Step 2: Using laser etching technology, windmill-shaped metamaterial structural units are etched onto the glass surface coated with an FTO thin film. The metamaterial structural units have a side length of 8 mm. Figure 2 As shown, the dimensions of each part in the windmill-shaped metamaterial structural unit are a=0.8 mm, b=0.8 mm, c=0.8 mm, d=3.2 mm, e=1.2 mm, and f=4.8 mm, respectively; the laser etching uses a 1064 nm laser with an etching rate of 40 mm / s and a spot diameter of 30 μm.

[0060] Step 3: The glass etched with metamaterial in Step 2 is bonded to another piece of optically transparent glass (2 mm thick) using a commercially available organic film with a thickness of 1 mm. The hot-pressing conditions are: temperature 60 ℃, pressure 0.6 MPa, and time 12 min. The above steps are repeated. Finally, a first transparent glass layer, a first metamaterial stacking unit (windmill-shaped structure), a second transparent glass layer, a transparent conductive film, a third transparent glass layer, a second metamaterial stacking unit (windmill-shaped structure), and a fourth transparent glass layer are prepared from top to bottom. During hot pressing, a PVB organic film is used, and the temperature is maintained at 60 ℃ and the pressure at 0.6 MPa for 12 min. At the same time, nitrogen gas (purity 99.999%) with a flow rate of 40 sccm is introduced to avoid the generation of bubbles. The resulting metamaterial-based optically transparent bidirectional absorbing glass has an optically transparent glass layer thickness of 2 mm and a metamaterial stacking unit thickness of 1 mm.

[0061] Testing revealed that the metamaterial-based optically transparent bidirectional absorbing glass exhibits an absorption rate exceeding 85% in the 9.6-20.3 GHz frequency range and an average transmittance of 78% in the visible light band. Combined with... Figure 3The energy loss density diagram reveals that electromagnetic wave loss is concentrated on the metamaterial pattern at the interface. This electromagnetic loss is caused by ohmic loss in the resonant structure, which explains the intrinsic absorption mechanism of the metamaterial glass, where electromagnetic loss is caused by resonant coupling effect. The application scenario of the metamaterial-based optically transparent bidirectional absorbing glass is the side window of the cockpit of a military helicopter. It can cope with early warning radar detection in the frequency band of 9.6~20.3 GHz. The FTO film can withstand extreme temperature differences of -50~80℃, and the 78% visible light transmittance can ensure a clear view for the pilot. The combination of 2 mm thick glass and 1 mm thick film also improves the resistance to airflow impact.

[0062] Example 3 This embodiment provides a method for preparing metamaterial-based optically transparent bidirectional absorbing glass, including the following steps: Step 1: Select an optically transparent glass (specifically silicate glass) with a thickness of 3 mm, and use indium tin oxide (ITO) as the transparent conductive material; deposit an ITO thin film on the glass surface using thermomagnetron sputtering technology; the thermomagnetron sputtering uses an ITO target doped with 10 wt% SnO2, introduces pure argon gas (purity of 99.999%) and controls the flow rate at 30 sccm, and sets the sputtering power to 220 W, ultimately forming an ITO thin film with a thickness of 150 nm.

[0063] Step 2: Using laser etching, windmill-shaped and square superimposed metamaterial structural units are etched on the glass surface coated with ITO thin film. The side length of the metamaterial structural unit is 12 mm. The laser etching uses a 1064 nm laser with an etching speed of 35 mm / s and a spot diameter of 40 μm.

[0064] Step 3: The glass engraved with metamaterials is hot-pressed with another piece of optically transparent glass (3 mm thick) using a 1.5 mm thick organic film (commercially available). The hot-pressing conditions are: temperature 50 ℃, pressure 0.3 MPa, and time 15 min. The above steps are repeated. Finally, a first transparent glass layer, a first metamaterial stacking unit (windmill-shaped and square stacked structure), a second transparent glass layer, a transparent conductive film, a third transparent glass layer, a second metamaterial stacking unit (windmill-shaped and square stacked structure), and a fourth transparent glass layer are prepared from top to bottom. During hot pressing, PVB organic film is used, and the temperature is maintained at 50 ℃ and the pressure at 0.3 MPa for 15 min. At the same time, nitrogen gas (purity 99.999%) with a flow rate of 40 sccm is introduced to avoid the generation of bubbles. The resulting metamaterial-based optically transparent bidirectional absorbing glass has an optically transparent glass layer thickness of 3 mm and a metamaterial stacking unit thickness of 1.5 mm.

[0065] The metamaterial-based optically transparent bidirectional absorbing glass exhibits an absorption rate exceeding 85% in the 25-40 GHz frequency range and an average transmittance of 72% in the visible light band. Figure 4 As shown. The application scenario of the metamaterial-based optically transparent bidirectional absorbing glass is as a transparent partition in the 5G millimeter-wave base station equipment room. It can shield the millimeter-wave radiation of the base station in the 25~40 GHz frequency band to avoid interference with surrounding equipment. The electromagnetic protection efficiency of the ITO film is ≥-30 dB, the 3 mm thick quartz glass can withstand the high temperature of 40~50 ℃ in the equipment room, and the PC film can resist the influence of high humidity environment.

[0066] Example 4 This embodiment provides a method for preparing metamaterial-based optically transparent bidirectional absorbing glass, including the following steps: Step 1: Select an optically transparent glass (specifically silicate glass) with a thickness of 1.5 mm. The transparent conductive material is aluminum-doped zinc oxide (AZO). AZO thin film is deposited on the glass surface using thermomagnetron sputtering technology. The thermomagnetron sputtering uses an AZO target doped with 3wt% Al2O3, purged with argon gas (99.999% purity) at a flow rate of 22 sccm, and a power of 180 W, ultimately forming a 90 nm thick AZO thin film.

[0067] Step 2: Using laser etching technology, windmill-shaped, square, and ring-shaped superimposed metamaterial structural units are etched onto the glass surface coated with an FTO thin film. The side length x of each metamaterial structural unit is 10 mm. Figure 5A , Figure 5B As shown, the laser etching uses a 532 nm green laser with an etching speed of 30 mm / s and a spot diameter of 20 μm. A stacked structure with a side length of 10 mm is etched by partitioned scanning.

[0068] Step 3: The glass with the metamaterial pattern etched in Step 2 is bonded to another piece of optically transparent glass (1.5 mm thick) using two 1 mm thick organic films (commercially available). The hot-pressing conditions are: temperature 70 ℃, pressure 0.6 MPa, and time 10 min. Repeat the above steps. Finally, a first transparent glass layer and a first metamaterial stacking unit (windmill-shaped 13, square 14, and ring 15 stacked together by organic films 12) are fabricated from top to bottom. Figure 5A , Figure 5BAs shown, each metamaterial stacking unit has a side length x of 10 mm, a second transparent glass layer, a transparent conductive film, a third transparent glass layer, a second metamaterial stacking unit (a combination of windmill-shaped, square, and ring-shaped stacks), and a fourth transparent glass layer. During hot pressing, PVB organic film is used, and the temperature is maintained at 70°C and pressure at 0.6 MPa for 10 minutes. At the same time, nitrogen gas (purity of 99.999%) with a flow rate of 40 sccm is introduced to avoid the generation of bubbles, thus obtaining the metamaterial-based optically transparent bidirectional absorbing glass. The thickness of its optically transparent glass layer is 1.5 mm, and the thickness of its metamaterial stacking unit is 2 mm.

[0069] The metamaterial-based optically transparent bidirectional absorbing glass exhibits an absorption rate exceeding 85% in the 2-19 GHz frequency range. Figure 6 The average transmittance in the visible light band is 76%. The metamaterial-based optically transparent bidirectional absorbing glass is used as an optical reconnaissance window for small reconnaissance drones. The ultra-wide frequency band of 2~19 GHz can cope with various electromagnetic detections. The 1.5mm thick aluminosilicate glass makes the weight of a 10 cm×10 cm window only 37.5g, which meets the lightweight requirements of drones. The EVA film has a high degree of cross-linking and can resist flight vibrations of 10~500 Hz.

[0070] Example 5 This embodiment provides a method for preparing metamaterial-based optically transparent bidirectional absorbing glass, including the following steps: Step 1: Select an optically transparent glass (specifically silicate glass) with a thickness of 2.5 mm, and use fluorine-doped arsenic dioxide (FTO) as the transparent conductive material; deposit an FTO thin film on the surface of the optically transparent glass using thermomagnetron sputtering technology; the thermomagnetron sputtering uses an FTO target doped with 6 wt% F, and introduces argon gas (99.999% purity) and oxygen gas mixed in a volume ratio of 92:8 with a total flow rate controlled at 28 sccm and a power set at 250 W, ultimately forming an FTO thin film with a thickness of 110 nm.

[0071] Step 2: Using laser etching technology, windmill-shaped and square superimposed metamaterial structural units are etched on the glass surface coated with FTO thin film. The side length of the metamaterial structural unit is 16 mm. The laser etching uses a 1064 nm laser with an etching speed of 45 mm / s and a spot diameter of 60 μm. The windmill-shaped and square structures with a side length of 16 mm are fabricated by splicing the etching.

[0072] Step 3: The glass with the etched metamaterial from Step 2 is bonded to another piece of optically transparent glass (2.5 mm thick) using a 3 mm thick organic film (commercially available). The hot-pressing conditions are: temperature 80 ℃, pressure 0.7 MPa, time 5 min. Repeat the above steps. Finally, the following layers are prepared from top to bottom: first transparent glass layer, first metamaterial stacking unit (windmill-shaped and square stacked structure), second transparent glass layer, transparent conductive film, third transparent glass layer, second metamaterial stacking unit (windmill-shaped and square stacked structure), and fourth transparent glass layer. During hot pressing, PVB organic film is used, and the temperature is maintained at 80 ℃ and pressure at 0.7 MPa for 5 min. At the same time, nitrogen gas (purity 99.999%) with a flow rate of 40 sccm is introduced to avoid the generation of bubbles. The resulting metamaterial-based optically transparent bidirectional absorbing glass has an optically transparent glass layer thickness of 2.5 mm and a metamaterial stacking unit thickness of 3 mm.

[0073] The metamaterial-based optically transparent bidirectional absorbing glass exhibits an absorption rate exceeding 90% in the 5-13 GHz frequency range and an average transmittance of 74% in the visible light band. Its application scenario is as an observation window in the command cabin of a naval frigate. The 5-13 GHz frequency band is suitable for the stealth requirements of shipborne radar. The FTO film is resistant to 5 wt% seawater salt spray, and the combination of 2.5 mm thick glass and 3 mm thick film provides an impact resistance of 150 kJ / m², enabling it to withstand wave impacts and ensure the safety of personnel inside the cabin.

[0074] Example 6 This embodiment provides a method for preparing metamaterial-based optically transparent bidirectional absorbing glass, including the following steps: Step 1: Select an optically transparent glass (specifically silicate glass) with a thickness of 3 mm, and use aluminum-doped zinc oxide (AZO) as the transparent conductive material; deposit an AZO thin film on the glass surface using thermomagnetron sputtering technology; the thermomagnetron sputtering uses an AZO target doped with 2 wt% Al2O3, introduces argon gas (purity of 99.999%) with a flow rate controlled at 18 sccm, and sets the power to 160 W, ultimately forming an AZO thin film with a thickness of 85 nm.

[0075] Step 2: Using laser etching technology, square and ring-shaped superimposed metamaterial structural units are laser-etched on the glass surface coated with FTO thin film. The side length of the metamaterial structural unit is 16 mm. The laser etching uses a 532 nm laser with an etching speed of 55 mm / s and a spot diameter of 55 μm.

[0076] Step 3: The glass etched with metamaterial in Step 2 is hot-pressed with another piece of optically transparent glass (3 mm thick) using a 0.5 mm thick organic film (commercially available). The hot-pressing conditions are: temperature 30 ℃, pressure 0.7 MPa, time 10 min. The above steps are repeated. Finally, the following layers are prepared from top to bottom: first transparent glass layer, first metamaterial stacking unit (square and ring stacking structure), second transparent glass layer, transparent conductive film, third transparent glass layer, second metamaterial stacking unit (square and ring stacking structure), and fourth transparent glass layer. During hot pressing, PVB organic film is used, and the temperature is maintained at 30 ℃ and pressure at 0.7 MPa for 10 min. At the same time, nitrogen gas (purity 99.999%) with a flow rate of 40 sccm is introduced to avoid the generation of bubbles. The resulting metamaterial-based optically transparent bidirectional absorbing glass has a thickness of 3 mm for the optically transparent glass layer and a thickness of 0.5 mm for the metamaterial stacking unit.

[0077] The metamaterial-based optically transparent bidirectional absorbing glass has an absorption rate of over 85% in the 18-38 GHz frequency range and an average light transmittance of 73% in the visible light band. The application scenario for the metamaterial-based optically transparent bidirectional absorbing glass is the side window of the driver's cab of high-speed trains. The 18-38 GHz frequency band can reduce interference from 5G private networks and train control signals along the line. The 3 mm thick quartz glass does not crack at a low temperature of -30℃, making it suitable for the winter environment in the north. Moreover, the low-temperature hot pressing ensures that the flatness of the window is ≤0.1 mm / m, which does not affect the driver's driving vision.

[0078] Numerous specific details are set forth in this specification. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some embodiments, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0080] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A metamaterial-based optically transparent bidirectional absorbing glass, characterized in that, The transparent bidirectional absorbing glass is a multi-layered gradient structure constructed from an optically transparent glass layer and a transparent conductive thin film metamaterial layer; wherein, the transparent conductive thin film metamaterial layer is etched on the surface of the optically transparent glass layer, and the optically transparent glass layer is connected by an organic film.

2. The metamaterial-based optically transparent bidirectional absorbing glass according to claim 1, characterized in that, The transparent conductive thin film metamaterial layer is a stacked structural unit consisting of windmill-shaped, square, and ring-shaped components on and under an organic film.

3. The metamaterial-based optically transparent bidirectional absorbing glass according to claim 1, characterized in that, The transparent bidirectional absorbing glass includes, from the surface to the core, a first transparent glass layer, a first metamaterial stacking unit, a second metamaterial stacking unit, a second transparent glass layer, a conductive transparent film, a third transparent glass layer, a third metamaterial structural unit, a fourth metamaterial stacking unit, and a fourth transparent glass layer.

4. The metamaterial-based optically transparent bidirectional absorbing glass according to claim 3, characterized in that, The thickness of the first, second, third, and fourth transparent glass layers is 1~3 mm; the side length of the first, second, third, and fourth metamaterial stacking units is 8~16 mm; and the thickness of the first, second, third, and fourth metamaterial stacking units is 0.5~4 mm.

5. The metamaterial-based optically transparent bidirectional absorbing glass according to claim 1, characterized in that, The transparent conductive film is made of aluminum-doped zinc oxide, fluorine-doped arsenic dioxide, or indium tin oxide, and its thickness is 85~150 nm; the metamaterial-based optically transparent bidirectional absorbing glass has an absorption rate of over 85% in the frequency range of 5~40 GHz.

6. A method for preparing a metamaterial-based optically transparent bidirectional absorbing glass according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: A transparent conductive thin film is deposited by thermomagnetron sputtering, a metamaterial pattern is etched by laser, and the glass and organic film are bonded together by hot pressing to obtain the metamaterial-based optically transparent bidirectional absorbing glass.

7. The preparation method according to claim 6, characterized in that, The parameters for the thermomagnetron sputtering are set as follows: argon flow rate of 18~30 sccm, target sputtering power of 80~150 W, and substrate temperature of 60~120 ℃; the parameters for the laser etching are set as follows: laser wavelength of 355~1064 nm, power of 10~30 W, and scanning speed of 100~500 mm / s; the parameters for the hot pressing are set as follows: temperature of 120~160 ℃, pressure of 0.5~1.2 MPa, and hot pressing time of 15~30 min.

8. A transparent absorbing glass, characterized in that, The transparent absorbing glass is the metamaterial-based optically transparent bidirectional absorbing glass according to any one of claims 1-5; the transparent absorbing glass includes an electromagnetic wave transmission channel, a metamaterial carrier, and an electromagnetic wave absorption layer, wherein the electromagnetic wave transmission channel and the metamaterial carrier are optically transparent glass layers; and the electromagnetic wave absorption layer is a transparent conductive thin film metamaterial layer.

9. A type of architectural glass, characterized in that, The architectural glass is the metamaterial-based optically transparent bidirectional absorbing glass as described in any one of claims 1-5.

10. A transparent window, characterized in that, The transparent window adopts the metamaterial-based optically transparent bidirectional absorbing glass according to any one of claims 1-5, and the transparent window includes any one of aircraft cockpit glass, ship and vehicle viewing windows, UAV optical reconnaissance windows, and high-speed train driver's cab windows.

Images