All-dielectric film system structure with visible near-infrared high absorption, intermediate infrared selective radiation and microwave high transmission

Abstract

The invention provides an all-dielectric film system structure with visible near-infrared high absorption, intermediate infrared selective radiation and microwave high transmission. The all-dielectric film system structure sequentially comprises a protection and antireflection layer, a visible near-infrared absorption and infrared selective radiation layer and a substrate layer from top to bottom, the protection and antireflection layer comprises a first dielectric layer and a second dielectric layer which are arranged up and down; the visible near-infrared absorption and infrared selective radiation layer comprises a plurality of third dielectric layers and fourth dielectric layers which are alternately stacked. According to the structure, high absorption can be achieved in the wave band of 380-1100 nm, high reflection (low radiation) can be kept in the wave bands of 3-5 m and 8-14 m, high transmissivity is achieved in the microwave wave band, certain radiation can be kept in the wave bands of 5-8 m and 14-25 m, and effective heat management is achieved. The all-dielectric film system structure also considers the stability of the material in a space environment, and is provided with a protection and antireflection layer, so that the potential application reliability of the film system is improved.

Description

Technical Field

[0001] The present invention belongs to the field of multi-spectral stealth technology, and specifically relates to an all-dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission. Background Art

[0002] With the rapid development of modern detection technology, single-band stealth is no longer sufficient to meet practical needs. The need for comprehensive stealth technology encompassing the visible, infrared, and microwave bands is becoming increasingly urgent. This is particularly true for platforms operating in darkness, such as satellites and high-altitude aircraft. These platforms not only need to reduce their detectability in the visible, near-infrared, and primary infrared atmospheric windows (3-5µm and 8-14µm), but also effectively manage the heat generated by their own operation and the heat absorbed from external radiation to ensure stable operation and extend the lifespan of the onboard equipment in the extreme space environment. Furthermore, to ensure that their communication and detection functions are not compromised, stealth materials must also possess excellent microwave transmission properties.

[0003] Currently, there have been several studies on multispectral camouflage films. For example, the paper "Nanostructured Ge / ZnSFilms for Multispectral Camouflage with Low Visibility and Low Thermal Emission" proposes a multifunctional photonic film based on a Ge / ZnS nanostructure. This film achieves high absorption in the visible and near-infrared regions through the high loss of Ge in the visible light band and its gradient refractive index design. It also utilizes the lossless properties of Ge / ZnS in the infrared band and the photonic bandgap effect to achieve low thermal radiation at the atmospheric window. Furthermore, the low electrical conductivity of the material allows for high microwave transmittance. However, the film structure described in this paper primarily focuses on visible light camouflage and low radiation at the infrared atmospheric window, and insufficiently considers the thermal management issues faced by spacecraft in the actual space environment. In particular, in a vacuum environment, thermal convection and heat conduction are greatly suppressed, and radiation heat dissipation becomes the primary heat dissipation method. In order to maintain a safe operating temperature of the device (usually between -20°C and +50°C, with some sensitive devices such as batteries and optical sensors requiring a narrower range) and balance the heat generated by the device with the heat absorbed by solar radiation, a certain radiation heat dissipation capability is required in the non-atmospheric window bands (such as 5-8µm and 14-25µm).

[0004] Furthermore, traditional stealth materials, such as those based on metal substrates or thick metal layers, while capable of achieving low radiation in the infrared, often struggle to maintain high microwave transmittance. Approaches based on coatings or composite materials can also face challenges in multispectral compatibility, manufacturing complexity, cost, and adaptability to space environments.

[0005] Therefore, developing a new type of membrane structure that can achieve high absorption in the visible and near-infrared, low radiation in the infrared atmospheric window, and high transmission of microwaves, while taking into account effective radiation heat dissipation in the non-atmospheric window band and having good stability in the space environment, has important theoretical research value and practical application prospects. Summary of the Invention

[0006] To address the challenges of existing technologies, the present invention provides an all-dielectric film system with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission. This structure not only achieves high absorption in the visible and near-infrared bands of 380-1100nm, maintains high reflection (low radiation) in the 3-5µm and 8-14µm infrared atmospheric window bands, and exhibits high microwave transmittance, but also maintains a certain radiation capacity in the non-atmospheric window bands of 5-8µm and 14-25µm for effective heat management. Furthermore, the present all-dielectric film system takes into account the material's stability in space environments.

[0007] A fully dielectric film structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission, comprising, from top to bottom, a protective and anti-reflection layer, a visible and near-infrared absorption and infrared selective radiation layer, and a substrate layer;

[0008] The protection and anti-reflection layer includes a first dielectric layer and a second dielectric layer arranged one above the other;

[0009] The visible-near infrared absorption and infrared selective radiation layer includes a plurality of alternately stacked third dielectric layers and fourth dielectric layers, and the film layer close to the substrate layer is the third dielectric layer.

[0010] The protective and anti-reflection layer consists of one or more layers of dielectric materials that are stable to space environments (such as ultraviolet radiation and atomic oxygen) and possess specific optical properties. This layer primarily protects the internal functional layers from the space environment while further optimizing the anti-reflection effect in the visible and near-infrared bands through refractive index matching, thereby increasing absorptivity. The dielectric layers used in this all-dielectric film system are all low-conductivity dielectric materials, and the overall thickness of all dielectric layers is negligible compared to the microwave wavelength, ensuring the film system's high microwave transmittance.

[0011] Preferably, the first dielectric layer is selected from a material with a refractive index of 1 to 2;

[0012] The second dielectric layer is selected from a material with a refractive index of 2 to 3;

[0013] The third dielectric layer is selected from a material with a refractive index of 3 to 5;

[0014] The fourth dielectric layer is selected from materials with a refractive index of 1-3.

[0015] As a further preference, the material of the first dielectric layer is SiO2, Al2O3, MgO, BeO, GeO2, MgF2, CaF2, BaF2, AlF3, YF3, YbF3, LaF3, Na3AlF6, PTFE, PEEK, PET, PMMA, PC, PDMS, CYTOP or optical glue;

[0016] The second dielectric layer material is TiO2, CeO2, ZrO2, HfO2, TeO2, Y2O3, Yb2O3, Bi2O3, Sc2O3, ZnO, CdO, Nb2O5, Ta2O5, V2O5, TiO x , ZnS, ZnSe, Si3N4, AlN or Al x Ti 1-x N;

[0017] The material of the third dielectric layer is Ge, Si, Te, III-V compound, II-VI compound or chalcogenide alloy and chalcogenide glass;

[0018] The fourth dielectric layer material is SiO2, Al2O3, MgO, BeO, GeO2, MgF2, CaF2, BaF2, AlF3, YF3, YbF3, LaF3, Na3AlF6, PTFE, PEEK, PET, PMMA, PC, PDMS, CYTOP, optical glue, TiO2, CeO2, ZrO2, HfO2, TeO2, Y2O3, Yb2O3, Bi2O3, Sc2O3, ZnO, CdO, Nb2O5, Ta2O5, V2O5, TiO x , ZnS, ZnSe, Si3N4, AlN or Al x Ti 1-x N.

[0019] Among them, III-V compounds include but are not limited to GaAs, In x Ga 1-x As, InSb; II-VI compounds include but are not limited to CdTe; chalcogenide alloys and chalcogenide glasses include but are not limited to GST, GSST, GSS in various stoichiometric ratios and PbS, PbSe, PbTe, Sb2S3, Sb2Se3.

[0020] As further preferred, the material of the first dielectric layer is SiO2 or MgF2;

[0021] The second dielectric layer material is TiO2 or ZnO;

[0022] The third dielectric layer is made of Ge or Si;

[0023] The fourth dielectric layer is made of ZnS or HfO 2 .

[0024] As a specific preference, the material of the first dielectric layer is SiO2;

[0025] The material of the second dielectric layer is TiO2;

[0026] The material of the third dielectric layer is Ge;

[0027] The fourth dielectric layer is made of ZnS.

[0028] Preferably, in the visible-near-infrared absorption and infrared selective radiation layer, the film layer close to the protection and anti-reflection layer is the third dielectric layer.

[0029] Preferably, the visible-near-infrared absorption and infrared selective radiation layer is composed of a third dielectric layer / (fourth dielectric layer / third dielectric layer)^8 from top to bottom.

[0030] Preferably, the substrate layer is made of an infrared radiation material selected from polyimide, polytetrafluoroethylene, polyurethane, methyl methacrylate, and glass. Black polyimide (BC-PI) is further preferred. The substrate layer is a flexible material with broadband high absorption properties. When the film system overlying it transmits light in a specific heat dissipation band to the substrate layer, the synergistic effect of the film system and the absorbing substrate achieves heat dissipation from the non-atmospheric window.

[0031] Preferably, the thickness of the first dielectric layer is 20-100 nm;

[0032] The thickness of the second dielectric layer is 20-100 nm;

[0033] The thickness of the third dielectric layer is 5 to 1000 nm;

[0034] The thickness of the fourth dielectric layer is 10-1200 nm.

[0035] As a further preference, in order from top to bottom, the thickness of the first third dielectric layer is 5-15 nm; the thickness of the first fourth dielectric layer is 5-30 nm; the thickness of the remaining third dielectric layers is 150-950 nm; and the thickness of the fourth dielectric layer is 400-1000 nm.

[0036] As a further preferred embodiment, the thickness of the first dielectric layer is 70-90 nm;

[0037] The thickness of the second dielectric layer is 30-50 nm.

[0038] As a specific preference, the all-dielectric film system structure with high absorption in the visible and near-infrared, selective radiation in the mid-infrared and high transmission in microwaves is SiO2 (82 nm) / TiO2 (38 nm) / Ge (7 nm) / ZnS (21 nm) / Ge (692 nm) / ZnS(993 nm) / Ge (745 nm) / ZnS (414 nm) / Ge (882 nm) / ZnS (407 nm) / Ge (742nm) / ZnS (1000 nm) / Ge (891 nm) / ZnS (463 nm) / Ge (166 nm) / ZnS (451 nm) / Ge (917 nm) / ZnS (570 nm) / Ge (801 nm) / BC-PI.

[0039] For the visible-near-infrared absorption part: the present invention utilizes a combination of a high-refractive-index and high-loss material film layer (the third dielectric layer) and a low-refractive-index material film layer (the fourth dielectric layer) to achieve strong absorption of solar radiation in the 380-1100 nm band through thin-film interference, refractive-index gradient matching, and intrinsic absorption of the material.

[0040] For the low-radiation part of the infrared atmospheric window: the present invention uses a photonic crystal-like structure constructed from lossless or low-loss infrared transparent materials with high and low refractive index contrast to form high-reflection bands in the 3-5 µm and 8-14 µm atmospheric window bands through the photonic band gap effect, thereby achieving low emissivity.

[0041] Regarding the non-atmospheric window radiation heat dissipation part: the present invention precisely controls the overall structure of the multi-layer film system and utilizes the thin film interference effect to make the film system as a whole exhibit higher transmittance or lower reflectivity in the target non-atmospheric window bands (5-8 µm and 14-25 µm), and achieves heat dissipation by utilizing the substrate layer with high absorption (i.e. high radiation) characteristics.

[0042] The all-dielectric film system structure of the present invention with high absorption in the visible and near-infrared, selective radiation in the mid-infrared, and high transmission of microwaves can achieve high absorption in the visible to near-infrared band, low radiation in the infrared atmospheric window band, and radiative heat dissipation in the specific non-atmospheric window infrared band, and at the same time has high microwave transmittance, and is particularly suitable for stealth of aerospace vehicles requiring thermal management.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. Achieving synergy between spectral functions and thermal management compatibility: The all-dielectric film structure proposed in this paper not only achieves multispectral stealth with high absorption in the visible and near-infrared, low radiation in the infrared atmospheric window, and high microwave transmission, but more importantly, by designing effective radiative heat dissipation channels in specific non-atmospheric infrared bands (5-8 µm and 14-25 µm), it overcomes the lack of thermal management considerations in existing similar research. This is of great significance for ensuring the stable operation of spacecraft internal components on orbit, extending their lifespan, and improving overall stealth effectiveness.

[0045] 2. Excellent spectral selectivity: The all-dielectric film structure of the present invention exhibits excellent performance indicators in the target band, such as extremely high visible light absorptivity, extremely low atmospheric window emissivity, and high non-atmospheric window emissivity, and strong spectral selectivity.

[0046] 3. Good potential for adaptability to space environments: The all-dielectric film system of the present invention takes into account the protection against environmental factors such as space ultraviolet rays and atomic oxygen through the design of the outer protective layer, thereby improving the potential application reliability of the film system.

[0047] 4. High design feasibility: The all-dielectric membrane structure of the present invention uses mature thin film materials, has a relatively simple structure, and the number of layers is within an acceptable range, making large-scale production possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the membrane structure in an embodiment of the present invention;

[0049] In the figure, 1 is the first dielectric layer; 2 is the second dielectric layer; 3 is the third dielectric layer; 4 is the fourth dielectric layer; 5 is the substrate layer;

[0050] Figure 2 This is a physical diagram of the membrane structure in an embodiment of the present invention;

[0051] Figure 3 This is a visible-near infrared absorption spectrum of the film structure according to an embodiment of the present invention;

[0052] Figure 4 This is a mid-infrared radiation spectrum diagram of the film structure in an embodiment of the present invention;

[0053] Figure 5 This is a microwave transmission spectrum diagram of the film structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention are further described in detail below with reference to the accompanying drawings and embodiments.

[0055] like Figure 1 As shown, a full dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation and high microwave transmission includes, from top to bottom, a protection and anti-reflection layer, a visible and near-infrared absorption and infrared selective radiation layer, and a substrate layer 5.

[0056] The protection and anti-reflection layer comprises a first dielectric layer 1 and a second dielectric layer 2 from top to bottom. The materials of the first dielectric layer / the second dielectric layer are preferably SiO2 / TiO2, respectively. The specific thicknesses of the first dielectric layer / the second dielectric layer are 82 nm and 38 nm, respectively.

[0057] The visible-near-infrared absorption and infrared selective radiation layer is composed of a third dielectric layer / (fourth dielectric layer / third dielectric layer)^8 from top to bottom. The materials of the third dielectric layer / fourth dielectric layer are preferably Ge / ZnS, respectively. The specific structure is Ge (ZnS / Ge)^8, and the specific thicknesses of the structure are: Ge (7 nm) / ZnS (21 nm) / Ge (692 nm) / ZnS (993 nm) / Ge (745 nm) / ZnS (414 nm) / Ge (882 nm) / ZnS (407 nm) / Ge(742 nm) / ZnS (1000 nm) / Ge (891 nm) / ZnS (463 nm) / Ge (166 nm) / ZnS(451 nm) / Ge (917 nm) / ZnS (570 nm) / Ge (801 nm). The total thickness of the structure is 10.282 µm. Since the total thickness is negligible compared to the microwave wavelength and the materials are all low-conductivity dielectrics, it has high transmittance in the microwave band.

[0058] The material of the substrate layer 5 is a broadband high-absorption flexible medium, preferably BC-PI (black polyimide).

[0059] The actual picture of the prepared all-dielectric film structure with high visible near-infrared absorption, selective mid-infrared radiation and high microwave transmission is as follows: Figure 2 shown.

[0060] Performance testing:

[0061] Visible-NIR absorption spectroscopy was used to measure the reflectivity R and transmittance T using a UV-Visible-NIR spectrophotometer, where the absorbance A=1-RT.

[0062] The visible-near infrared absorption spectrum of the all-dielectric film structure prepared above is as follows: Figure 3 As shown. Figure 3It can be seen that the absorptivity of the film structure in the entire visible-near-infrared band of 380-1100 nm (the shaded part in the figure) exceeds 0.99; specifically, its average absorptivity reaches 0.9906, which significantly reduces the reflectivity in the 380-1100 nm band, thereby reducing the detectability in the visible-near-infrared band.

[0063] The mid-infrared radiation spectrum is measured by Fourier transform infrared spectrometer (FTIR) to measure the reflectivity R. For opaque samples, the emissivity ε=1-R.

[0064] The infrared radiation spectrum of the all-dielectric film structure prepared above is as follows: Figure 4 As shown by Figure 4 As can be seen, within the 3-5µm and 8-14µm atmospheric window bands, the infrared emissivity is as low as 0.1029 and 0.1052, respectively, effectively suppressing thermal radiation within the infrared atmospheric window and reducing the risk of detection by infrared thermal imagers. Within the 5-8µm and 14-25µm non-atmospheric window bands, the infrared emissivity is 0.6421 and 0.5807, respectively. The higher emissivity in these non-atmospheric window bands helps effectively dissipate heat generated within the device and absorbed solar radiation to the surrounding environment, thereby assisting in thermal management of aerospace vehicles.

[0065] Microwave transmittance was measured in a microwave anechoic chamber using a vector network analyzer using the bow method.

[0066] The microwave transmission spectrum of the all-dielectric film structure prepared above is shown in Figure 5 As shown. Figure 5 It can be seen that in the 5-40 GHz frequency band, the film structure has extremely high transmittance. Specifically, its average transmittance reaches 0.9845, which meets the requirements of microwave communication.

[0067] In this embodiment, by optimizing the thickness combination of SiO2, TiO2, ZnS, and Ge layers, the overall film structure not only achieves high absorption and low emissivity in the visible near-infrared and infrared atmospheric window bands, but also maintains high transmittance in the microwave band. Furthermore, through optimized design, heat can be effectively transmitted to the BC-PI absorbing substrate and radiated from the substrate in the non-atmospheric window bands of 5-8 µm and 14-25 µm, thus providing an effective radiation heat dissipation channel. The synergistic effect of this multi-layer nanofilm structure enables the film to achieve excellent spectral selectivity and heat dissipation performance, making it suitable for aerospace platforms such as satellites and high-altitude aircraft that require low visible light and infrared detectability under dark backgrounds, compatibility with microwave communications, and effective thermal management.

[0068] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. The present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A fully dielectric film structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission, characterized in that: From top to bottom, it includes a protection and anti-reflection layer, a visible near-infrared absorption and infrared selective radiation layer, and a substrate layer; The protection and anti-reflection layer includes a first dielectric layer and a second dielectric layer arranged one above the other; The visible near-infrared absorption and infrared selective radiation layer includes a plurality of alternately stacked third dielectric layers and fourth dielectric layers, and the film layer close to the substrate layer is the third dielectric layer.

2. The all-dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission according to claim 1 is characterized in that: The first dielectric layer is selected from a material with a refractive index of 1 to 2; The second dielectric layer is selected from a material with a refractive index of 2 to 3; The third dielectric layer is selected from a material with a refractive index of 3 to 5; The fourth dielectric layer is selected from materials with a refractive index of 1-3.

3. The all-dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission according to claim 2 is characterized in that: The material of the first dielectric layer is SiO2, Al2O3, MgO, BeO, GeO2, MgF2, CaF2, BaF2, AlF3, YF3, YbF3, LaF3, Na3AlF6, PTFE, PEEK, PET, PMMA, PC, PDMS, CYTOP or optical glue; The second dielectric layer material is TiO2, CeO2, ZrO2, HfO2, TeO2, Y2O3, Yb2O3, Bi2O3, Sc2O3, ZnO, CdO, Nb2O5, Ta2O5, V2O5, TiO x , ZnS, ZnSe, Si3N4, AlN or Al x Ti 1-x N; The material of the third dielectric layer is Ge, Si, Te, III-V compound, II-VI compound or chalcogenide alloy and chalcogenide glass; The fourth dielectric layer material is SiO2, Al2O3, MgO, BeO, GeO2, MgF2, CaF2, BaF2, AlF3, YF3, YbF3, LaF3, Na3AlF6, PTFE, PEEK, PET, PMMA, PC, PDMS, CYTOP, optical glue, TiO2, CeO2, ZrO2, HfO2, TeO2, Y2O3, Yb2O3, Bi2O3, Sc2O3, ZnO, CdO, Nb2O5, Ta2O5, V2O5, TiO x , ZnS, ZnSe, Si3N4, AlN or Al x Ti 1-x N.

4. The all-dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission according to claim 1 is characterized in that: In the visible near infrared absorption and infrared selective radiation layer, the film layer close to the protection and anti-reflection layer is the third dielectric layer.

5. The all-dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission according to claim 1 is characterized in that: The visible near-infrared absorption and infrared selective radiation layer is composed of a third dielectric layer / (fourth dielectric layer / third dielectric layer)^8 from top to bottom.

6. The all-dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission according to claim 1 is characterized in that: The substrate layer material is an infrared radiation material selected from one of polyimide, polytetrafluoroethylene, polyurethane, methyl methacrylate and glass.

7. The all-dielectric film system structure with high visible and near-infrared absorption, selective mid-infrared radiation, and high microwave transmission according to claim 1 is characterized in that: The thickness of the first dielectric layer is 20-100 nm; The thickness of the second dielectric layer is 20-100 nm; The thickness of the third dielectric layer is 5 to 1000 nm; The thickness of the fourth dielectric layer is 10-1200 nm.

Images