Laser protection device based on a rolled composite film and method for manufacturing same

Abstract

The application belongs to the technical field of laser protection, and particularly relates to a laser protection device based on a curled vanadium dioxide composite film structure and a preparation method thereof. The laser protection device comprises a calcium fluoride glass substrate and an array of curled three-dimensional structure units prepared on the substrate; the three-dimensional structure units in the array comprise a vanadium dioxide film, a chromium film and a silver film, the composite film is curled into a three-dimensional structure from a planar state through a self-curling technology; wherein the vanadium dioxide film is an excited actuating layer, the chromium film is an adhesion layer and a stress layer, and the silver film is a laser reflection layer. The application utilizes the thermal deformation of the vanadium dioxide film and the reflection function of the silver film to realize intelligent protection of not affecting light transmission when there is no laser and self-developing reflected laser when laser is incident. The device has a simple preparation method, low cost, can be produced on a large scale, and has wide practical significance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser protection, and particularly relates to a laser protection device based on a curled vanadium dioxide composite film structure and a preparation method thereof. BACKGROUND

[0002] The monochromaticity, strong directionality, high brightness and excellent coherence of laser make it have great application potential in military and civilian fields. Especially in the military field, including laser blinding, laser guidance, laser ranging, laser aiming, etc., have developed into mature weapon systems and played an important role. Especially the laser blinding weapon, through the destruction of various photoelectric detectors by strong laser, realizes the blinding of enemy reconnaissance systems, becomes an important part of the war, and even affects the whole war situation. In addition, strong laser also has a great threat to the human eye. Common laser weapons are usually concentrated in the 0.5-10um wave band, such as 0.93um GaAs, 1.54um and 10.6um CO2, etc.

[0003] For laser protection, at present, it is mainly limited to two-dimensional scale, and is usually protected according to the following several ways: (1) selecting a material with high visible light transmittance and high infrared reflectivity, such as ITO, zinc oxide, indium oxide, etc. They are almost completely transparent in the visible light band, but almost not transparent in the region with a wavelength of 2um or more, mainly by reflection. This kind of infrared protective cover can block the infrared laser radiation above 2um without reaction time, but the disadvantage is also obvious, that is, it can only act on the detector in the visible light band, and the detector in the infrared band will lose its working ability because it cannot transmit infrared, and it also cannot block the short-wavelength laser. (2) Another common laser protection material is a phase change material based on vanadium dioxide. There is a huge change in infrared transmittance before and after the phase change. Usually, before the phase change, it shows a high infrared transmittance at low temperature, and after the phase change due to laser irradiation, the infrared transmittance is greatly reduced, mainly by reflection and absorption (the reflectivity is slightly higher than the absorption). This makes vanadium dioxide become an intelligent laser protection cover based on infrared detectors. However, the visible light transmittance of vanadium dioxide itself is low, which cannot be used for laser protection of visible light detectors (cannot work normally at low temperature), and there is still a certain infrared absorption under laser irradiation, which will cause a certain damage to the equipment. Therefore, we need an infrared laser protection device that can be applied to longer wave band detection equipment, and the protection device needs to have higher reflectivity to ensure that the damage of laser to the detection equipment is as small as possible. SUMMARY

[0004] The application aims to provide a laser protection device with good protection performance and stable reliability and a preparation method thereof.

[0005] The laser protection device provided by the application is based on a curled vanadium dioxide composite film structure, and comprises a calcium fluoride glass (CaF2) substrate and a two-dimensional array of curled three-dimensional structure units prepared on the substrate; the three-dimensional structure unit in the array is composed of a composite film of a vanadium dioxide (VO2) film, a chromium (Cr) film and a silver (Ag) film, and the three-dimensional structure unit is a square when unfolded into a plane, the side length of the square is 180-250 um (preferably the side length of the square is 180-200 um, and more preferably the side length of the square is 200 um), and the square pattern interval is 30-100 um (preferably the square pattern interval is 30-50 um, and more preferably the square pattern interval is 30 um); the curling radius of the curled three-dimensional structure unit is 50-110 um; wherein the vanadium dioxide film is a stimulated actuation layer, the chromium film is an adhesion layer and a stress layer, and the silver film is a laser reflection layer. Each structure unit can work independently, and the number of working structures depends on the size of the infrared laser irradiation area.

[0006] Wherein:

[0007] The surface of the calcium fluoride glass substrate is flat, and has a visible light and infrared transmittance close to 100% in the 0.13-12 um wave band;

[0008] The thickness of the vanadium dioxide film is 60-80 nm, the thickness of the chromium film is 10-50 nm, and the thickness of the silver film is 50-60 nm;

[0009] The vanadium dioxide film is a phase change material and can produce deformation before and after the phase change temperature (68℃), driving the chromium film and the silver film to curl or flatten;

[0010] The silver film has a great reflection function for infrared light, avoiding direct damage of the laser to the lens;

[0011] The chromium film plays an adhesion role and transmits stress.

[0012] The application utilizes the stress gradient generated by the lattice mismatch of vanadium dioxide, chromium and silver to realize the preparation of the curled structure.

[0013] The preparation method of the laser protection device based on the curled vanadium dioxide composite film provided by the application comprises the following specific steps:

[0014] (1) Selecting a substrate; the calcium fluoride glass is used as the substrate; the surface of the substrate is flat, and has a visible light and infrared transmittance close to 100% in the 0.13-12 um wave band; the calcium fluoride glass is cleaned by using acetone, ethanol and water respectively for 8-12 minutes;

[0015] (2) Preparing a sacrifice layer: a silicon dioxide is deposited on the surface of the calcium fluoride glass by a magnetron sputtering method as a sacrifice layer, and the thickness is 80-150 nm;

[0016] (3) Preparation of vanadium dioxide film: vanadium dioxide film is grown on the surface of the silicon dioxide film by a magnetron sputtering method, and the thickness is 60-80 nm;

[0017] (4) Photoetching of pattern array: square patterns (M*N) are photoetched on the surface of the vanadium dioxide film in a two-dimensional array, each square pattern has a side length of 180-250 um (preferably, the square pattern has a side length of 180-200 um, and more preferably, the square pattern has a side length of 200 um), and the square pattern spacing is 30-100 um (preferably, the pattern spacing is 30-50 um, and more preferably, the pattern spacing is 30 um);

[0018] (5) In the patterned area, chromium film and silver film are sequentially deposited by an electron beam evaporation method, the thickness of the chromium film is 10-50 nm, and the thickness of the silver film is 50-60 nm;

[0019] (6) The silicon dioxide sacrificial layer is selectively etched to obtain a curled vanadium dioxide / chromium / silver film array, and the curling radius is 50-110 um; in order to protect the upper vanadium dioxide / chromium / silver film from being corroded, hydrofluoric acid is used as the etching solution.

[0020] In step (2), the surface roughness of the silicon dioxide film is controlled to be less than 5 nm, so as to ensure the deposition of the vanadium dioxide film and the high-quality preparation of the curled array.

[0021] In step (3), the specific process of preparing the vanadium dioxide film by the magnetron sputtering method is as follows: the target material is a metal vanadium target, a direct current power source of 200 W is used, the flow rate ratio of oxygen and argon is kept at 35:62 sccm, the target surface is pre-sputtered for 10 min to remove the oxidation layer, the vanadium dioxide film is grown for 1000 s when the temperature rises to 550 DEG C, and the sample is taken out after cooling to room temperature.

[0022] The laser protection device based on the curled vanadium dioxide composite film provided by the application has the protection principle that, at room temperature (without laser irradiation), the curled structure of the vanadium dioxide / chromium / silver film array is in a curled state, the curled structure exposes the calcium fluoride glass substrate, and lens light (visible light to near-infrared light) can pass through the calcium fluoride glass without obstruction, so that the detector behind the protection device can normally work; when strong laser irradiates the lens and causes the temperature to rise, the curled vanadium dioxide drives the upper metal to automatically change from the curled state to the planar state due to the phase change caused by the temperature, and the upper metal is completely flattened on the calcium fluoride glass substrate; since the silver film has a great reflection effect on infrared light, the direct damage of the laser to the lens can be avoided. After the laser irradiation disappears, the temperature returns to room temperature, and the vanadium dioxide / chromium / silver film on the surface of the calcium fluoride glass returns to the initial curled state.

[0023] The application uses a vanadium dioxide / chromium / silver composite film to prepare a novel laser protection device based on three-dimensional passive mechanical actuation light control through a self-rolling technique, which breaks through the bottleneck of laser protection of a two-dimensional scale single material system.

[0024] The application utilizes the light transmittance of the rolled laser protection device at room temperature to enhance the light transmittance, which does not affect the work of the detector lens; after phase transition and expansion, the silver film and the vanadium dioxide film highly reflect infrared light, and isolate the destruction of infrared laser to the equipment behind the protective cover. The three-dimensional protection device is stable and reliable, economical, and can be mass-produced. Each rolled structure is a separate individual, which can work in a single structure or in a large area in cooperation.

[0025] The originality of the application lies in that the strain generated by the rolled film during heating is used to realize the transition of the rolled film from the rolled state to the flat state, and this change is spontaneous according to the environmental conditions without providing energy. Meanwhile, the switching between the two states does not hinder the normal work of the detector, and automatically protects when danger comes, which also plays a warning function. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Figure 1 is a schematic diagram of the working principle of the laser protection device based on the transparent rolled vanadium dioxide composite film array of the application. Wherein (a) is a low-temperature normal working state, and (b) is a strong radiation protection state.

[0027] Figure 2 Figure 2 is the shape change of multiple rolled structures after being irradiated by strong light. Wherein (a) is no light irradiation, and (b) is strong power light irradiation.

[0028] Figure 3 Figure 3 is the shape change of a single rolled structure after being irradiated by an infrared laser spot.

[0029] Figure 4 Figure 4 is the reflectivity test results of the laser protection devices prepared by different methods of the application at different temperatures. Wherein, (a) is prepared by Example 1, (b) is prepared by Example 1, and (c) is prepared by Example 3. IMPLEMENTATION

[0030] The following embodiments and drawings further illustrate the laser protection device based on the rolled vanadium dioxide / chromium / silver composite film and the protection effect. The following embodiments are used to illustrate the application, but not as a limitation on the content of the application.

[0031] Preparation of the laser protection device based on the rolled vanadium dioxide composite film:

[0032] (1) Take a 1 cm × 1 cm calcium fluoride glass as a substrate, and clean it with acetone, ethanol and deionized water in sequence for ten minutes, and dry it in a nitrogen flow.

[0033] (2) The cleaned calcium fluoride glass was used as a substrate and placed in the PVD75 magnetron sputtering machine produced by Kurt J. Lesker to deposit a silicon dioxide thin film. The target material was silicon dioxide, the RF power supply was 200W, the total sputtering time was 1200s, and the oxygen-argon ratio was maintained at 5:60.

[0034] (3) After the silica deposition is completed, the chamber is continuously evacuated for ten minutes before depositing a vanadium dioxide film. The target material is a vanadium metal target. A DC power supply of 200W is used, the total sputtering time is 1000s, and the oxygen-argon ratio is maintained at 35:62. During the heating process, pre-sputtering is performed for 10 minutes to remove the oxide layer on the target surface. When the temperature rises to 550℃, the vanadium dioxide film is grown. After the growth is completed, the sample is naturally cooled to room temperature and taken out. The thickness of the vanadium dioxide film is 60-80nm.

[0035] (4) Using the KW-4A spin coater from China Xinyouyan Co., Ltd., spin coater onto the surface of the vanadium dioxide film. Figure 1 A layer of photoresist was applied; the photoresist model was AZ-5214 positive photoresist; the low rotation speed was 600 rpm for 6 seconds; the high rotation speed was 4000 rpm for 60 seconds; then it was placed on a hot plate and pre-baked at 90°C for 90 seconds; a 9mm × 9mm square array was lithographically patterned using a SUSS MA6 UV lithography machine from Germany, with each square having a side length of 200µm and a spacing of 30µm between the square patterns; the lithographically patterned substrate was immersed in RZX-3038 positive photoresist developer from Suzhou Ruihong Electronic Chemicals Co., Ltd. for 35 seconds, then rinsed with deionized water, and dried with nitrogen flow to obtain the lithographic substrate; then, vanadium dioxide portions in the lithographic pattern were etched away by passing CF430sccm through a reactive ion etching instrument, and the photoresist was removed after ultrasonic cleaning with ethanol for 30 seconds, resulting in a vanadium dioxide thin film substrate with etched window patterns;

[0036] (5) Following the same method as above, perform another spin coating and photolithography to obtain the window for depositing the metal layer;

[0037] (6) Using the Tianxingda TSV700 electron beam evaporator, chromium and silver films were deposited sequentially. The target materials used were 99.99% chromium and 99.9% silver, respectively. First, a chromium film with a thickness of 10-50 nm was deposited on the vanadium dioxide surface at a rate of 0.07 nm / s. After that, it was left to stand for 10 minutes. Then, a silver film with a thickness of 50-60 nm was deposited at a rate of 0.1 nm / s. After cooling for 40 minutes, the sample was taken out by opening the cavity.

[0038] (7) The prepared vanadium dioxide / chromium / silver composite film is etched with hydrofluoric acid, and after about 5 minutes, it is placed in the cavity of an Autosamdri-815B Series B supercritical drying instrument of the U.S. Tousimis company filled with ethanol; after the drying program is completed, the sample is taken out, and a curled vanadium dioxide / chromium / silver film structure array is obtained.

[0039] In this way, the preparation of the infrared laser protection cover based on the curled structure of the vanadium dioxide / chromium / silver film is completed. The working schematic diagram is as shown in Figure 1 The simulated laser irradiation environment is irradiated by using a high-power infrared heat lamp. When the infrared light intensity increases (directly irradiating the object can make the surface reach 200°C), the curled vanadium dioxide / chromium / silver film structure automatically unfolds into a planar state, as shown in Figure 2 The curled structure is also irradiated by using an 808nm laser. Due to the small spot size, the energy cannot be transmitted to the entire structure, but through the shape change of the curled structure under the side-view microscope, it can be inferred that the time required for the protection mechanism to start is about 6.7ms, as shown in Figure 3

[0040] According to the above experimental method, in order to verify the reliability and performance optimization of the structure, different curled structure diameters are prepared by adjusting the thickness of the chromium film. Embodiment

[0041] The photoetching pattern is kept unchanged, and a 10nm chromium film is deposited on the surface of vanadium dioxide at a rate of 0.07nm / s. After the end, it is left for 10 minutes. Then a silver film is deposited at a rate of 0.1nm / s, with a thickness of 50-60nm. After cooling for 40 minutes, the sample is taken out. The prepared vanadium dioxide / chromium / silver composite film is etched with hydrofluoric acid, and after supercritical drying, a curled vanadium dioxide / chromium / silver film structure array is obtained, with a curled radius of about 50um. The reflectivity test results at different temperatures are as shown in Figure 4 (a), which has the lowest room temperature reflectivity and excellent high temperature reflectivity, can realize low temperature without affecting the equipment operation and high temperature reflectivity laser. Embodiment

[0042] The photoetching pattern is kept unchanged, and a 10nm chromium film is deposited on the surface of vanadium dioxide at a rate of 0.07nm / s. After the end, it is left for 10 minutes. Then a silver film is deposited at a rate of 0.1nm / s, with a thickness of 50-60nm. After cooling for 40 minutes, the sample is taken out. The prepared vanadium dioxide / chromium / silver composite film is etched with hydrofluoric acid, and after supercritical drying, a curled vanadium dioxide / chromium / silver film structure array is obtained, with a curled radius of about 50um. The reflectivity test results at different temperatures are as shown in Figure 4 ​(b) shown, with certain room temperature reflectivity and excellent high temperature reflectivity, to some extent, to achieve low temperature does not affect the device, high temperature reflective laser. Embodiments

[0043] The photolithography pattern is kept unchanged, and a 50 nm chromium film is deposited on the vanadium dioxide surface at a rate of 0.07 nm / s, and after the end, it is left for 10 minutes. Then a silver film is deposited at a rate of 0.1 nm / s, with a thickness of 50-60 nm. After cooling for 40 minutes, the sample is taken out of the cavity. The prepared vanadium dioxide / chromium / silver composite film is etched with hydrofluoric acid, and after supercritical drying, a curled vanadium dioxide / chromium / silver film structure array is obtained, with a curling radius of about 50 um. The reflectivity test results at different temperatures are as shown in Figure 4 (c) shown, the room temperature reflectivity and the high temperature reflectivity are not much different, which shows that the curled structure tube diameter is large and is not conducive to normal operation at room temperature.

Claims

1. A laser protection device based on a rolled vanadium dioxide composite film, characterized in that, The application relates to a two-dimensional array comprising a fluorite glass substrate and a three-dimensional structure unit rolled on the substrate. The three-dimensional structure unit in the array is composed of a composite film of a vanadium dioxide film, a chromium film and a silver film, the three-dimensional structure unit is a square when unfolded into a plane, the side length of the square is 189-250 um, and the square pattern interval is 30-100 um; the rolling radius of the rolled three-dimensional structure unit is 50-110 um; wherein the vanadium dioxide film is a stimulated actuation layer, the chromium film is an adhesion layer and a stress layer, and the silver film is a laser reflection layer; each structure unit works independently, and the number of working structure units depends on the size of the infrared laser irradiation area.

2. The laser protection device of claim 1, wherein, The fluorite glass substrate has a smooth surface and a visible light and infrared transmittance close to 100% in the 0.13-12 um wave band.

3. The laser protection device of claim 1, wherein, The vanadium dioxide film has a thickness of 60-80 nm, the chromium film has a thickness of 10-50 nm, and the silver film has a thickness of 50-60 nm.

4. A method for preparing a laser protection device based on a rolled vanadium dioxide composite film, characterized in that, The specific steps are as follows: (1) selecting a substrate; the fluorite glass is used as the substrate; the substrate surface is smooth, and has a visible light and infrared transmittance close to 100% in the 0.13-12 um wave band; (2) preparing a sacrifice layer; a silicon dioxide film is deposited on the fluorite glass surface by a magnetron sputtering method, and is used as the sacrifice layer and has a thickness of 80-150 nm; (3) preparing a vanadium dioxide film; a vanadium dioxide film is grown on the surface of the silicon dioxide film by a magnetron sputtering method, and has a thickness of 60-80 nm; (4) photoetching a square pattern two-dimensional array on the surface of the vanadium dioxide film, the side length of each square pattern is 180-250 um, and the square pattern interval is 30-100 um; (5) depositing a chromium film and a silver film on the patterned area by an electron beam evaporation method in sequence, the chromium film has a thickness of 10-50 nm, and the silver film has a thickness of 50-60 nm; (6) selectively etching the silicon dioxide sacrifice layer to obtain a rolled vanadium dioxide / chromium / silver film array, and the rolling radius is 50-110 um; a hydrofluoric acid is used as the etching solution.

5. The preparation method according to claim 4, characterized in that, In step (2), the surface roughness of the silicon dioxide film is controlled to be below 5 nm.

6. The production method according to claim 4, characterized by, In step (3), the specific process of preparing the vanadium dioxide film by the magnetron sputtering method is as follows: the target material is a metal vanadium target, a direct current power source of 200 W is adopted, the oxygen and argon flow rate ratio is kept at 35:62 sccm, the target material surface is pre-sputtered for 10 min to remove the oxide layer, the vanadium dioxide film is grown for 1000 s when the temperature is raised to 550 DEG C, and the sample is taken out after being cooled to room temperature.

Images