High-transmittance laser broadband anti-reflection film with 9.2-10.7 mu m and preparation method thereof

Abstract

The application discloses a kind of high transmittance 9.2-10.7 μm laser broadband antireflection film and preparation method thereof, a kind of high transmittance 9.2-10.7 μm laser broadband antireflection film, its film system structure is:SUB / k1Lk2H1k3Lk4H2 / AIR, wherein, SUB represents zinc sulfide base, AIR represents air, H1 represents zinc sulfide layer, H2 represents zinc sulfide layer, L represents YB layer, YB layer is the mixed film layer of the volume ratio of aluminum-doped YF3 and calcium-doped BaF2 (2-3):1, k1-k4 represent the coefficient of the optical thickness of quarter reference wavelength of each layer.This application high transmittance 9.2-10.7 μm laser broadband antireflection film, average single-side reflectivity is not more than 0.08%, average double-side transmittance is not less than 99.78%, and by film material selection and collocation, film stress is basically eliminated, improve the adhesion of film layer, and the wear resistance of obtained film layer is strong, and high and low temperature resistance is good.

Description

Technical Field

[0001] The invention relates to a laser broadband anti-reflection film with high transmittance of 9.2-10.7 μm and a preparation method thereof, belonging to the technical field of laser broadband high-efficiency anti-reflection films. Background Art

[0002] In optical components, light energy is lost due to reflection from the component surface. In order to reduce the reflection loss on the component surface, a transparent dielectric film is often coated on the surface of the optical component. This film is called an anti-reflection film.

[0003] During the preparation process of an antireflection coating, optical properties such as reflectivity and transmittance in the corresponding wavelength band must be considered. Mechanical properties such as film stress and adhesion must also be considered. A balanced approach to optical and mechanical properties is crucial to meeting application requirements. The presence of film stress can directly lead to phenomena such as film shedding and color cracking, severely impacting product performance. Therefore, reducing or even eliminating film stress is crucial in the preparation of an antireflection coating. Reflectivity and transmittance are crucial parameters for evaluating the performance of an antireflection coating. Due to their importance to optical components, numerous researchers have dedicated themselves to the development of these coatings, achieving considerable success in reducing their reflectivity and increasing their transmittance. For example, patent application number CN202010731907.0 discloses an antireflection film for a sapphire substrate and its preparation method. The film exhibits a transmittance of approximately 97% and a reflectivity of approximately 1.5%. However, with increasing customer demands for product quality, the optical performance of antireflection coatings needs further improvement. Summary of the Invention

[0004] The present invention provides a laser broadband anti-reflection film with high transmittance of 9.2-10.7 μm and a preparation method thereof. The average single-side reflectivity is no more than 0.08%, the average double-side transmittance is no less than 99.78%, and the stress of the film layer is basically eliminated, the adhesion of the film layer is improved, and the obtained film layer has strong wear resistance and good high and low temperature resistance.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A high-transmittance 9.2-10.7μm laser broadband anti-reflection film, whose film structure is: SUB / k1Lk2H1k3Lk4H2 / AIR, wherein SUB represents a zinc selenide substrate, AIR represents air, H1 represents a zinc selenide layer, H2 represents a zinc sulfide layer, L represents a YB layer, and the YB layer is a mixed film layer with a volume ratio of (2-3):1 of aluminum-doped YF3 and calcium-doped BaF2. k1-k4 represent the coefficients of the optical thickness of one-quarter of the reference wavelength of each layer.

[0007] The above-mentioned antireflection film, through the selection and matching of film layers, basically eliminates the film layer stress and improves the film layer adhesion. The resulting film layer has strong wear resistance and good high and low temperature resistance. The average single-side reflectivity of the antireflection film is not more than 0.08%, and the average double-side transmittance is not less than 99.78%.

[0008] For antireflection coatings, different wavelength bands require different substrates and different film systems. The zinc sulfide layer and zinc selenide layer selected in this application have extremely low scattering loss and high tolerance to thermal shock. By plating the YB layer, zinc selenide layer and zinc sulfide layer on the zinc selenide substrate in a specific order, the stress problem between the film layers is effectively solved, the density of the film layer is improved, the film layer is made stronger, and the wear resistance and temperature resistance are improved. At the same time, the single-sided reflectivity is reduced to below 0.08%, and the double-sided transmittance is increased to above 99.78%.

[0009] The selection of aluminum-doped YF3 and calcium-doped BaF2 in the mixed film layer, on the one hand, reduces the stress of the film layer by doping with a specific amount of aluminum and calcium, and on the other hand, reduces the single-sided reflectivity of the film layer.

[0010] In order to better balance the optical and mechanical properties, the aluminum content in the aluminum-doped YF3 is 2wt%-6wt%; the calcium content in the calcium-doped BaF2 is 1wt%-20wt%.

[0011] The above-mentioned high transmittance 9.2-10.7μm laser broadband anti-reflection film is double-sided coated, and the film structure is AIR / H2k4Lk3H1k2Lk1 / SUB / k1Lk2H1k3Lk4H2 / AIR.

[0012] The values ​​of k1-k4 are related to the reference wavelength λ. When the reference wavelength is 10600 nm, the value of k1 is 0.03-0.06, the value of k2 is 2.20-2.60, the value of k3 is 0.30-0.60, and the value of k4 is 0.10-0.35.

[0013] In order to better balance the optical and mechanical properties of the antireflection coating, k1L is the first YB layer, k2H1 is the zinc selenide layer, k3L is the second YB layer, and k4H2 is the zinc sulfide layer; the physical thickness of the first YB layer is 100±20nm, the physical thickness of the zinc selenide layer is 2680±100nm, the physical thickness of the second YB layer is 970±50nm, and the physical thickness of the zinc sulfide layer is 285±20nm.

[0014] The above-mentioned high transmittance 9.2-10.7 μm laser broadband antireflection film has a stress close to 0 calculated by surface profile. In this application, the calculated value is considered to be approximately equal to 0 if its absolute value is less than 0.05 GPa.

[0015] This application uses the Newton ring method formula Calculate the film stress. When the film diameter is more than 50 times larger than the thickness, the film stress σ can be derived by measuring the curvature radius r of the interference factor, where ts is the substrate thickness, t f is the film thickness, Es is the Young's modulus of elasticity of the substrate, and ν is the Poisson's ratio of the substrate.

[0016] The ultra-low stress 9.2-10.7μm laser broadband anti-reflection film is deposited using ion-assisted deposition during the coating process. Before coating, the zinc selenide substrate is baked at 100-130°C for 0.5-1h. The initial vacuum degree during film formation is (0.5-0.8)*10-3Pa, and the ion source parameters are set as follows: acceleration voltage 200V, plate voltage 450±50V, and beam current 5-100mA.

[0017] To further increase the density of the deposited film and improve its optical and mechanical properties, zinc selenide was evaporated using a molybdenum boat barrier evaporation method with an evaporation rate controlled at 0.3±0.05nm / s. Zinc sulfide was evaporated using a copper crucible electron beam evaporation method with an evaporation rate controlled at 0.6±0.1nm / s.

[0018] When the YB layer is evaporated, aluminum-doped YF3 and calcium-doped BaF2 are first mixed in a volume ratio of (2-3):1, and then evaporated using a molybdenum boat, with the evaporation rate controlled at 0.5±0.1 nm / s.

[0019] The technologies not mentioned in this invention are all referred to the prior art.

[0020] The laser broadband anti-reflection film with high transmittance of 9.2-10.7 μm of the present invention has an average single-side reflectivity of no more than 0.08% and an average double-side transmittance of no less than 99.78%. The stress of the film layer is basically eliminated through the selection and matching of film materials, and the adhesion of the film layer is improved. The obtained film layer has strong wear resistance and good high and low temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the high transmittance 9.2-10.7 μm laser broadband antireflection film in Example 1 of the present invention;

[0022] Figure 2 This is a single-side reflection curve diagram of the design of the high-transmittance 9.2-10.7 μm laser broadband anti-reflection film in Example 1 of the present invention;

[0023] Figure 3 This is a single-side reflection curve of the high transmittance 9.2-10.7 μm laser broadband anti-reflection film test in Example 1 of the present invention;

[0024] Figure 4This is a double-sided transmission curve of the high transmittance 9.2-10.7 μm laser broadband anti-reflection film test in Example 1 of the present invention;

[0025] Figure 5 A comparison of the profile changes before and after single-sided coating on the substrate in Example 1 of the present invention (the left side is before coating, and the right side is after coating);

[0026] In the figure, k1 to k4 represent corresponding film layers. DETAILED DESCRIPTION

[0027] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0028] Example 1

[0029] like Figure 1 As shown, a high-transmittance 9.2-10.7μm laser broadband anti-reflection film has a film structure of: AIR / H2k4Lk3H1k2Lk1 / SUB / k1Lk2H1k3Lk4H2 / AIR; where SUB represents the zinc selenide substrate, AIR represents air, H1 represents the zinc selenide layer, H2 represents the zinc sulfide layer, and L represents the YB layer. The YB layer is YF3 doped with 5wt% aluminum and 1.2wt% calcium. The value of k1 is 0.04, the value of k2 is 2.30, the value of k3 is 0.40, and the value of k4 is 0.15. The physical thickness of the k1L layer is 100nm, the physical thickness of the k2H1 layer is 2680nm, the physical thickness of the k3L layer is 970nm, and the physical thickness of the k4H2 layer is 285nm.

[0030] The high-transmittance 9.2-10.7μm broadband laser anti-reflection film was prepared using a Witnam 1100 coating machine and an INFICON IC6 controller. The film thickness is measured by changes in the quartz crystal's oscillation frequency. The ion source used was a Kaufman ion source developed by Zhongke Jiuzhang. The vacuum chamber relies on a mechanical pump, a diffusion pump, and a cryogenic unit system to achieve the required vacuum level for the film system. The vacuum level is measured using a thermocouple.

[0031] Before coating, the zinc selenide substrate was ultrasonically cleaned to remove the surface residue and baked at 100℃ for 1 hour. The initial vacuum degree during deposition was about 7.0*10 -4 Pa. The ion source parameters were set as: accelerating voltage 200V, screen voltage 400V, and beam current approximately 30mA. During film deposition, a Kaufman ion source was used to assist deposition, increasing the deposition density and improving structural integrity, thereby enhancing film performance and service life. Crystal control was employed to control the evaporation rate and film thickness.

[0032] ZnSe was evaporated using a molybdenum boat with a barrier evaporation rate of 0.3 nm / s, and ZnS was evaporated using a copper crucible with an electron beam evaporation rate of 0.6 nm / s. When the YB layer was evaporated, aluminum-doped YF3 and calcium-doped BaF2 were first mixed in a volume ratio of 2.5:1, and then evaporated using a molybdenum boat with a barrier evaporation rate of 0.5 nm / s.

[0033] Test results:

[0034] Optical performance test: The single-side reflectivity and double-side transmittance of the film were tested using an infrared spectrometer, and the obtained spectral curves met the design requirements: Figure 3-4 As shown in the figure, the average single-side reflectivity of 9.2-10.7μm is less than 0.08%, and the average double-side transmittance is greater than 99.78%. Figure 5 For the surface shown, the film stress is calculated to be -0.02GPa according to the Newton ring method.

[0035] Film performance test:

[0036] To ensure the reliability of optical components, the following environmental tests were conducted on the broadband antireflection coating sample in accordance with the requirements of GJB2485-95 General Specification for Optical Coatings:

[0037] (1) Abrasion resistance test: Wrap two layers of dry degreased gauze around the rubber friction head, and rub the film along the same trajectory under a pressure of 9.8N for 2000 times. There is no scratch or other damage to the film.

[0038] (2) Salt spray test: 35°C ambient temperature, 5% NaCl concentration, continuous spraying for 12 hours, two cycles, a total of 24 hours, no abnormality in the film layer.

[0039] (3) Immersion test: The sample is completely immersed in distilled water or deionized water. After one week, there is no abnormality in the film layer.

[0040] (4) High and low temperature test: constant temperature at -65℃ for 2 hours, quickly switch from -65℃ to 80℃ for 2 hours, then from 80℃ to -65℃ for 2 hours, cycle 12 times, and there is no abnormality in the film layer.

[0041] (5) Adhesion test: Use 1 cm wide 3M tape to stick firmly on the surface of the film layer. After quickly pulling up the tape from the edge of the part toward the surface in a vertical direction, the film layer will not fall off or be damaged. The above process is repeated 60 times, and the film layer will still not fall off or be damaged.

[0042] Comparative Example 1

[0043] The aluminum-doped YF3 and calcium-doped BaF2 in the YB layer were replaced with pure YF3 and BaF2, and the rest were referred to Example 1. The single-side reflectivity at 9.2-10.7 μm was 0.56%, and the calculated film stress result was -15.26 GPa.

[0044] Comparative Example 2

[0045] The calcium-doped BaF2 in the YB layer was omitted, and the rest was referred to Example 1. The single-side reflectivity at 9.2-10.7 μm was 1.21%, and the calculated film stress was -20.35 GPa.

[0046] Comparative Example 2

[0047] The aluminum-doped YF3 in the YB layer was omitted, and the rest were referred to Example 1. The single-side reflectivity at 9.2-10.7 μm was 1.93%, and the calculated film stress was -22.18 GPa.

Claims

1. A high transmittance 9.2-10.7 μm laser broadband antireflection film, characterized by: The film structure is: SUB / k1Lk2H1k3Lk4H2 / AIR, where SUB represents the zinc selenide substrate, AIR represents air, H1 represents the zinc selenide layer, H2 represents the zinc sulfide layer, L represents the YB layer, and the YB layer is a mixed film layer with a volume ratio of (2-3):1 of aluminum-doped YF3 and calcium-doped BaF2. k1-k4 represent the coefficients of the optical thickness of one-quarter of the reference wavelength of each layer. In aluminum-doped YF3, the aluminum content is 2wt%-6wt%.

2. The high transmittance 9.2-10.7 μm laser broadband antireflection film according to claim 1, characterized in that: In the calcium-doped BaF2, the doping amount of calcium is 1wt%-20wt%.

3. The high transmittance 9.2-10.7 μm laser broadband antireflection film according to claim 1 or 2, characterized in that: Double-sided coating, the film structure is AIR / H2k4Lk3H1k2Lk1 / SUB / k1Lk2H1k3Lk4H2 / AIR.

4. The high transmittance 9.2-10.7 μm laser broadband antireflection film according to claim 1 or 2, characterized in that: The value of k1 is 0.03~0.06, the value of k2 is 2.20~2.60, the value of k3 is 0.30~0.60, and the value of k4 is 0.10~0.

35.

5. The high transmittance 9.2-10.7 μm laser broadband antireflection film according to claim 1 or 2, characterized in that: k1L is the first YB layer, k2H1 is the zinc selenide layer, k3L is the second YB layer, and k4H2 is the zinc sulfide layer; the physical thickness of the first YB layer is 100±20nm, the physical thickness of the zinc selenide layer is 2680±100nm, the physical thickness of the second YB layer is 970±50nm, and the physical thickness of the zinc sulfide layer is 285±20nm.

6. The high transmittance 9.2-10.7 μm laser broadband antireflection film according to claim 1 or 2, characterized in that: The average single-side reflectivity is not greater than 0.08%, and the average double-side transmittance is not less than 99.78%.

7. The method for preparing a high transmittance 9.2-10.7 μm laser broadband antireflection film according to any one of claims 1 to 6, characterized in that: Zinc sulfide was evaporated by electron beam evaporation in a copper crucible, and the evaporation rate was controlled at 0.6±0.1nm / s.

8. The preparation method according to claim 7, wherein: Zinc selenide was evaporated using a molybdenum boat barrier evaporation method, and the evaporation rate was controlled at 0.3±0.05nm / s.

9. The preparation method according to claim 7, wherein: When the YB layer is evaporated, aluminum-doped YF3 and calcium-doped BaF2 are first mixed in a volume ratio of (2-3):1, and then evaporated using a molybdenum boat, with the evaporation rate controlled at 0.5±0.1nm / s.

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