Laser protection window based on vanadium dioxide film

Abstract

The invention relates to the technical field of laser protection, in particular to a vanadium dioxide film-based laser protection window, which comprises a substrate, a vanadium dioxide film, a first antireflection film, a metal absorption layer and a second antireflection film, a vanadium dioxide film and a first antireflection film are sequentially deposited on the front surface of the substrate, and a second antireflection film is deposited on the back surface of the substrate; the metal absorption layers are deposited at four different positions; the antireflection film is designed on the surface of the vanadium dioxide film, so that the transmittance of the window before phase change is improved, and the application requirement of high transmittance is met; meanwhile, a thin metal absorption layer is deposited on the antireflection film, and during laser irradiation, the metal layer quickly absorbs energy and transmits the energy to the vanadium dioxide film, so that the heating speed is increased, and quick response is realized; according to the structural design, the window can rapidly respond to lasers with different intensities, and continuous and effective protection on the lasers with the different intensities is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of laser protection, and in particular to a laser protection window based on a vanadium dioxide film. Background Art

[0002] With the rapid development of laser technology, the power and application areas of lasers are constantly expanding. In the military field, high-energy laser weapons have become important equipment in future wars; in the industrial field, laser cutting, welding and other processing technologies are widely used. However, strong lasers pose a potential threat to optical sensors, detectors and human eyes, and how to effectively protect against high-energy lasers has become an urgent problem to be solved.

[0003] Traditional laser protection methods mainly include: Passive protection: By coating the window material with an absorbent material or a reflective coating, the incident laser energy is absorbed or reflected. However, these methods have the disadvantages of low transmittance, being effective for specific wavelengths, and being easily affected by the environment.

[0004] Active protection: Use optoelectronic devices to detect incident lasers and quickly take measures such as blocking or shutting down. However, active protection systems are complex, costly, and have limited response speeds, making it difficult to deal with ultrafast laser threats.

[0005] Nonlinear optical protection: Utilize the nonlinear effects of optical materials, such as optical limiting and two-photon absorption, to achieve protection against high-energy lasers. However, these materials usually require high threshold energy excitation and have strict requirements on the working environment.

[0006] Vanadium dioxide (VO2) is a typical phase change material that undergoes a metal-insulator phase transition at around 68°C, with its optical, electrical and thermal properties changing significantly. By utilizing the phase change characteristics of VO2, an optical window with adaptive protection against lasers can be designed.

[0007] However, VO2 thin films still face the following challenges in practical applications: Response speed: The phase change process of pure VO2 film is limited by the thermal conduction and phase change dynamics of the material, and the response speed may not meet the rapid protection requirements of high-energy lasers.

[0008] Transmittance: The transmittance of VO2 film before and after phase change is quite different, but there is still room for improvement in the transmittance before phase change to meet the application requirements of high transmittance.

[0009] Working band: Different application fields have different requirements for the working band of the window, and the optical properties of the film need to be flexibly adjusted. Summary of the invention

[0010] In order to solve the problems of slow response speed, low transmittance and difficult adjustment of working band of VO2 thin film laser protection window in the prior art, the present invention provides a fast-response laser protection window based on vanadium dioxide, which can achieve efficient protection against lasers of different wavelengths and intensities and meet the application needs in multiple fields.

[0011] The present invention provides a laser protection window based on a vanadium dioxide film, wherein the laser protection window comprises a substrate, a vanadium dioxide film, a first anti-reflection film, a metal absorption layer and a second anti-reflection film; The vanadium dioxide thin film and the first anti-reflection film are deposited in sequence on the front side of the substrate, and the second anti-reflection film is deposited on the back side of the substrate; The metal absorption layer is deposited on the first antireflection film, or is deposited between the vanadium dioxide thin film and the first antireflection film, or is deposited on the second antireflection film, or is deposited between the substrate and the second antireflection film.

[0012] Furthermore, the vanadium dioxide film is prepared by magnetron sputtering, pulsed laser deposition or chemical vapor deposition, and the thickness of the vanadium dioxide film ranges from 100 nm to 500 nm.

[0013] Furthermore, the first anti-reflection film is formed by alternately depositing a high refractive index material and a low refractive index material, and the high refractive index material and the low refractive index material have a total of 4 to 10 layers.

[0014] Furthermore, the second anti-reflection film is formed by alternately depositing a high refractive index material and a low refractive index material, and the high refractive index material and the low refractive index material have 4 to 10 layers in total.

[0015] Furthermore, the high refractive index material is selected from one or more of metal germanium, zinc sulfide or titanium dioxide; and the low refractive index material is selected from one or more of silicon dioxide, aluminum oxide or magnesium fluoride.

[0016] Furthermore, the refractive index of the high refractive index material is greater than 2, and the refractive index of the low refractive index material is less than 1.7.

[0017] Furthermore, the thickness of the metal absorption layer ranges from 5 nm to 50 nm.

[0018] Furthermore, the metal material of the metal absorption layer is selected from chromium, nickel, titanium or aluminum.

[0019] Furthermore, the material of the substrate is selected from quartz glass, sapphire, metal germanium, zinc sulfide or optically transparent material.

[0020] Compared with the prior art, the present invention can achieve the following beneficial effects: High transmittance: In the entire structure, the transmittance of the laser protection window before phase change is improved by adopting anti-reflection film design, which can reach more than 90%, meeting the application requirements of high transmittance.

[0021] Fast response: By introducing a metal absorption layer, the vanadium dioxide film can absorb energy and undergo phase change more quickly under laser irradiation. The response time can be shortened to nanoseconds, meeting the requirements for rapid protection against high-energy lasers.

[0022] Tunability: By adjusting the thickness and material combination of each film layer in the entire laser protection window structure, the working band of the window can be flexibly designed to adapt to different application requirements.

[0023] Stable structure: By adopting mature film preparation technology and materials, the window structure is stable and has good environmental adaptability and service life.

[0024] Easy to manufacture: By adopting standard thin film deposition technology, it is easy to achieve large-area preparation and mass production, reducing manufacturing costs.

[0025] Although in general, the metal absorption layer has high thermal conductivity and fast optical absorption ability, and can quickly absorb energy and conduct heat at the moment of laser incidence; however, a single metal layer may increase optical reflection, reduce transmittance, and even introduce unnecessary light loss; the laser protection window based on vanadium dioxide film provided by the present invention creatively and cleverly combines the metal absorption layer with the vanadium dioxide layer and the anti-reflection film layer. The anti-reflection film reduces interface reflection and allows laser energy to enter the film system more effectively; the metal absorption layer quickly transfers the absorbed energy to the vanadium dioxide layer, accelerating its phase change process, thereby greatly shortening the response time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the working principle of a laser protection window according to an embodiment of the present invention; Figure 2 is a schematic structural diagram of a laser protection window according to an embodiment of the present invention; Figure 3 is a transmittance test curve diagram of a laser protection window according to an embodiment of the present invention; Figure 4 is a transmittance test curve diagram of the laser protection window after phase change according to an embodiment of the present invention; Figure 5 is a corresponding time comparison diagram of a laser protection window according to an embodiment of the present invention and a laser protection window according to a comparative example; Figure 6 is a schematic structural diagram of a laser protection window according to a second embodiment of the present invention; Figure 7is a schematic structural diagram of a laser protection window according to a third embodiment of the present invention; Figure 8 4 is a schematic diagram of the structure of the laser protection window according to the fourth embodiment of the present invention.

[0027] Reference numerals: 1. substrate 2. vanadium dioxide thin film 3. first antireflection film 4. second antireflection film 5. metal absorption layer. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0030] In a specific embodiment of the present invention, a laser protection window based on a vanadium dioxide thin film is provided, wherein the laser protection window comprises a substrate, a vanadium dioxide thin film, a first anti-reflection film, a metal absorption layer and a second anti-reflection film; the vanadium dioxide thin film and the first anti-reflection film are sequentially deposited on the front side of the substrate, and the second anti-reflection film is deposited on the back side of the substrate; the metal absorption layer is deposited on the first anti-reflection film, or is deposited between the vanadium dioxide thin film and the first anti-reflection film, or is deposited on the second anti-reflection film, or is deposited between the substrate and the second anti-reflection film; the metal absorption layer and the vanadium dioxide thin film are located on the same side of the substrate, that is, when the metal absorption layer is deposited on the first anti-reflection film, or is deposited between the vanadium dioxide thin film and the first anti-reflection film, the response time of the entire laser protection window is shorter and the performance is better; by designing an anti-reflection film on the surface of the vanadium dioxide thin film, the transmittance of the laser protection window before the phase change is improved, thereby meeting the application requirements of high transmittance. At the same time, a thin metal absorption layer is deposited on the anti-reflection film. When the laser is irradiated, the metal absorption layer quickly absorbs energy and transmits it to the vanadium dioxide film, accelerating its heating speed and achieving rapid response. This structural design enables the laser protection window to respond quickly to lasers of different intensities, achieving continuous and effective protection against lasers of various intensities.

[0031] The laser protection window provided in the specific embodiment of the present invention utilizes the phase change characteristics of the vanadium dioxide film and the rapid heating effect of the metal absorption layer, and uses it as a phase change protection material. It can quickly respond to lasers of different bands and intensities, and design a laser protection structure that can cope with various energies, thereby effectively attenuating and blocking laser interference signals, thereby achieving effective protection of the laser protection object.

[0032] In a specific embodiment, the vanadium dioxide film is prepared by magnetron sputtering, pulsed laser deposition or chemical vapor deposition. The phase change threshold of the vanadium dioxide film can be adjusted by adjusting its thickness, crystal structure and chemical composition. The thickness of the vanadium dioxide film ranges from 100nm to 500nm, which can obtain good phase change performance and optical properties. The first anti-reflection film and the second anti-reflection film are both formed by alternating deposition of high refractive index materials and low refractive index materials to improve the transmittance of the window before the phase change. The high refractive index material and the low refractive index material have a total of 4 to 10 layers. The number of layers of high refractive index material and low refractive index material in the first anti-reflection film and the second anti-reflection film can be the same or different; the high refractive index material is selected from one or more of metal germanium, zinc sulfide or titanium dioxide; the low refractive index material is selected from one or more of silicon dioxide, aluminum oxide or magnesium fluoride; the refractive index of the high refractive index material is greater than 2, and the refractive index of the low refractive index material is less than 1.7. The first anti-reflection film and the second anti-reflection film are both formed by alternating deposition of high refractive index materials and low refractive index materials, but overall, the low refractive index material layer is preferably selected as the top layer of the entire laser protection window based on vanadium dioxide film, that is, the layer in contact with the air, so as to better reduce interface reflection.

[0033] In a specific embodiment, the metal absorption layer is used to absorb the energy of the incident laser and quickly transmit it to the vanadium dioxide film, accelerating its temperature rise and causing it to rapidly undergo a phase change, thereby reducing the transmittance and achieving rapid protection against high-energy lasers; the material and thickness of the metal absorption layer have an important influence on the response speed, and preferably a metal material with a high absorption coefficient and high thermal conductivity is selected. Specifically, the metal material of the metal absorption layer is selected from chromium, nickel, titanium or aluminum, and the thickness of the metal absorption layer can range from 5nm to 50nm; more preferably, the thickness of the metal absorption layer is from 10nm to 30nm; it can improve the response speed while ensuring the transmittance.

[0034] In a specific implementation, the material of the substrate can be selected according to the working band, such as quartz glass is suitable for the near-infrared band, and zinc sulfide is suitable for a wider spectral range; specifically, the material of the matrix can be selected from quartz glass, sapphire, metallic germanium, zinc sulfide or other optically transparent materials, etc.

[0035] In the entire structure of the laser protection window provided in the specific embodiment of the present invention, the transmittance of the laser protection window before the phase change is improved by adopting an anti-reflection film design, which can reach more than 90%, meeting the application requirements of high transmittance. By introducing a metal absorption layer, the vanadium dioxide film can absorb energy faster and undergo a phase change under laser irradiation, and the response time can be shortened to nanoseconds, meeting the requirements for rapid protection against high-energy lasers. By adjusting the thickness and material combination of each film layer in the entire laser protection window structure, the operating band of the window can be flexibly designed to meet different application requirements. By adopting mature thin film preparation processes and materials, the window structure is stable and has good environmental adaptability and service life. By adopting standard thin film deposition technology, large-area preparation and mass production are easy to achieve, reducing manufacturing costs.

[0036] Next, the present invention will be specifically described in conjunction with embodiments. It should be understood that the following embodiments are only used to understand the present invention, but not to limit the present invention.

[0037] Example 1 Fast response laser protection window in 3μm band A zinc sulfide glass substrate 1 with a size of 50 mm × 50 mm × 1 mm was selected, which has good optical transmittance and thermal stability. The substrate was ultrasonically cleaned, and then cleaned in acetone, anhydrous ethanol and deionized water for 15 minutes each to remove surface organic matter and particles. The substrate was dried with high-purity nitrogen and placed in a clean environment for use.

[0038] Preparation of vanadium dioxide thin films In the vacuum magnetron sputtering equipment, the substrate 1 is fixed on the sample stage and the vacuum degree reaches 1×10⁻ 4 Pa. A vanadium (V) metal target with a purity of 99.99% was used as the sputtering source. High-purity argon and oxygen were filled, the gas flow ratio was controlled to be Ar:O=50:1, and the total pressure was 1Pa. The sputtering power was set to 150W, and the substrate temperature was kept at room temperature. The sputtering time was 90 minutes, and a vanadium dioxide film 2 with a thickness of about 300nm was obtained.

[0039] After the vanadium dioxide film 2 is deposited, the sample is annealed in an oxygen atmosphere at a temperature of 450° C. for 2 hours to improve the crystal quality and phase change characteristics of the film.

[0040] Design and deposition of AR coatings Anti-reflection coating material selection: High refractive index material: Titanium dioxide (TiO2), with a refractive index of approximately 2.4.

[0041] Low refractive index material: Silicon dioxide (SiO2), with a refractive index of approximately 1.46.

[0042] First AR coating design: The goal is to achieve minimum reflection and maximum transmittance at a wavelength of 3 μm. A quarter-wavelength four-layer film design is used to obtain the first antireflection film 3.

[0043] First AR coating deposition: In the electron beam evaporation equipment, the first antireflection film 3 designed as above is deposited in sequence. The temperature of the substrate 1 is controlled at 400° C. to improve the density and adhesion of the film layer. After each layer is deposited, optical monitoring is performed to ensure the accuracy of the film thickness.

[0044] On the surface of the first antireflection film 3, a 20 nm thick chromium Cr metal layer, namely the metal absorption layer 5, is deposited by magnetron sputtering method. The specific sputtering conditions are: sputtering power 50W, argon pressure 0.5Pa, sputtering time 5 minutes.

[0045] Deposition of the second antireflection coating on the back side On the back side of the substrate 1, a second anti-reflection film 4 is deposited using the same anti-reflection film design and deposition process as the front side to improve the overall transmittance.

[0046] Performance Testing Transmittance test: Use a spectrum test system to measure the transmittance of the window in the 3μm to 4μm band. Figure 3 As shown in Figure 1, before the phase change, the average transmittance of the window in the range of 3μm-4μm reaches 80%. After the phase change, as shown in Figure 1, Figure 4 As shown, the transmittance drops below 2%, achieving effective blocking of the laser.

[0047] Response speed test: Use a continuous laser (wavelength 3.7μm) to perform laser irradiation test. Detect the change of the transmitted light intensity of the window over time. Figure 5 As shown in the figure, after the absorption layer is plated, the response time is shorter than that without the absorption layer, which is only 1s.

[0048] Working principle: like Figure 1 As shown, the laser protection window provided by this embodiment maintains high transmittance and the signal is transmitted normally when the incident laser energy density is lower than the phase change threshold of the vanadium dioxide film 2; when the laser energy density exceeds the phase change threshold, the metal absorption layer 5 quickly absorbs energy and transmits it to the vanadium dioxide film 2, causing it to quickly phase change into a metallic state, and the transmittance decreases significantly, thereby achieving protection against high-energy lasers.

[0049] Example 2 A fast response laser protection window with a metal absorption layer plated on the back of the substrate 1 The difference between this embodiment and embodiment 1 is that Figure 6As shown, the metal absorption layer 5 is deposited on the back side of the substrate 1 instead of the front side.

[0050] A zinc sulfide (ZnS) substrate 1 that is the same as that in Example 1 is selected and cleaned and treated according to the method in Example 1.

[0051] On the front side of the substrate 1 , a vanadium dioxide thin film 2 and a first antireflection film 3 are sequentially deposited, and the process parameters are the same as those in the first embodiment.

[0052] Introduction of back metal absorption layer On the back side of the substrate 1, a second antireflection film 4 is first deposited, and then on the surface of the second antireflection film 4, a chromium Cr metal absorption layer 5 with a thickness of 20 nm is deposited by a magnetron sputtering method.

[0053] Transmittance test Use a spectrum test system to measure the transmittance of the window in the 3μm to 4μm band.

[0054] Response speed test A continuous laser (wavelength 3.7 μm) was used for laser irradiation test. The intensity of the transmitted light through the detection window was measured over time.

[0055] Results Analysis Since the metal absorption layer 5 is located on the back side, the incident laser must first pass through the vanadium dioxide film 2 and the first anti-reflection film 3, and then be absorbed by the metal absorption layer 5 on the back side and conduct heat, resulting in a slight decrease in the heating rate of the vanadium dioxide film 2 and a slight extension of the response time to 5s. However, the overall protection effect is still significant and can effectively protect against high-energy lasers.

[0056] The present invention significantly improves the response speed and protection performance of the laser protection window by introducing a metal absorption layer on the front or back of the vanadium dioxide film. By adjusting the design of the film layer, it can adapt to different application requirements and has a wide range of application prospects.

[0057] Example 3 like Figure 7 As shown, the difference between this embodiment and embodiment 1 is that the metal absorption layer 5 is deposited between the first antireflection film 3 and the vanadium dioxide film 2 .

[0058] Response speed test A continuous laser (wavelength 3.7 μm) was used for laser irradiation test. The intensity of the transmitted light through the detection window was measured over time.

[0059] The response time of the laser protection window corresponding to this embodiment is measured to be 2s. Combining Embodiment 1 and Embodiment 3, it can be seen that when the metal absorption layer 5 and the vanadium dioxide film 2 are deposited on the same side of the substrate 1, the performance of the entire laser protection window is better.

[0060] Example 4 like Figure 8 As shown, the difference between this embodiment and embodiment 1 is that the metal absorption layer 5 is deposited between the substrate 1 and the second antireflection film 4 .

[0061] Response speed test Use a continuous laser (wavelength 3.7μm) to perform laser irradiation test. Detect the change of the transmitted light intensity of the window over time.

[0062] The response time of the laser protection window corresponding to this embodiment is measured to be 8s, but the overall protection effect is still significant and can effectively protect against high-energy lasers.

[0063] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0064] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A laser protection window based on vanadium dioxide film, characterized in that: The laser protection window comprises a substrate, a vanadium dioxide film, a first anti-reflection film, a metal absorption layer and a second anti-reflection film; The vanadium dioxide thin film and the first anti-reflection film are deposited in sequence on the front side of the substrate, and the second anti-reflection film is deposited on the back side of the substrate; The metal absorption layer is deposited on the first antireflection film, or is deposited between the vanadium dioxide thin film and the first antireflection film, or is deposited on the second antireflection film, or is deposited between the substrate and the second antireflection film.

2. The laser protection window according to claim 1, characterized in that: The vanadium dioxide film is prepared by magnetron sputtering, pulsed laser deposition or chemical vapor deposition, and the thickness of the vanadium dioxide film ranges from 100 nm to 500 nm.

3. The laser protection window according to claim 1, characterized in that: The first anti-reflection film is formed by alternately depositing a high refractive index material and a low refractive index material, and the high refractive index material and the low refractive index material have 4 to 10 layers in total.

4. The laser protection window according to claim 1, characterized in that: The second anti-reflection film is formed by alternately depositing a high refractive index material and a low refractive index material, and the high refractive index material and the low refractive index material have 4 to 10 layers in total.

5. The laser protection window according to claim 3 or 4, characterized in that: The high refractive index material is selected from one or more of metal germanium, zinc sulfide or titanium dioxide; the low refractive index material is selected from one or more of silicon dioxide, aluminum oxide or magnesium fluoride.

6. The laser protection window according to claim 3 or 4, characterized in that: The refractive index of the high refractive index material is greater than 2, and the refractive index of the low refractive index material is less than 1.

7.

7. The laser protection window according to claim 1, characterized in that: The thickness of the metal absorption layer ranges from 5nm to 50nm.

8. The laser protection window according to claim 1, characterized in that: The metal material of the metal absorption layer is selected from chromium, nickel, titanium or aluminum.

9. The laser protection window according to claim 1, characterized in that: The material of the substrate is selected from quartz glass, sapphire, metal germanium, zinc sulfide or optically transparent materials.

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