阅读说明：本技术 一种高激光损伤阈值薄膜及其制备方法 (High laser damage threshold film and preparation method thereof ) 是由 梁玉 钟奇 于 2021-07-27 设计创作，主要内容包括：本发明涉及光学薄膜技术领域,具体来说涉及一种高激光损伤阈值薄膜及其制备方法,所述薄膜包括利用电子束蒸发制备前20层的介质膜；以及利用化学法溶胶凝胶法制备电场强度最大的最外4层膜层。本发明所提供的一种高激光损伤阈值薄膜及其制备方法,通过电子束蒸发与溶胶凝胶法相结合的方式,以及膜系结构设计与镀膜工艺的优化,制备在1064nm波段同时具有高反射率兼高损伤阈值的的光学薄膜,并且机械性能优异,薄膜牢固度强。同时可以有效的解决由于化学膜易扩撒等特点带来的镀制难题,镀制出的薄膜应力较小、附着力强,能在光学系统中正常稳定使用。(The invention relates to the technical field of optical films, in particular to a high laser damage threshold film and a preparation method thereof, wherein the film comprises a medium film of the front 20 layers prepared by electron beam evaporation; and preparing the outermost 4 film layers with the maximum electric field strength by using a chemical sol-gel method. According to the high laser damage threshold thin film and the preparation method thereof, the optical thin film which has high reflectivity and high damage threshold at the 1064nm waveband is prepared in a mode of combining electron beam evaporation and a sol-gel method and optimizing a film system structure design and a coating process, and the thin film is excellent in mechanical property and strong in film firmness. Meanwhile, the problem of difficult plating caused by the characteristic that a chemical film is easy to spread can be effectively solved, and the plated film has small stress and strong adhesive force and can be normally and stably used in an optical system.)

1. A high laser damage threshold film is characterized by comprising a dielectric film of the first 20 layers prepared by electron beam evaporation; and preparing the outermost 4 film layers with the maximum electric field strength by using a chemical sol-gel method.

2. The high laser damage threshold thin film of claim 1, wherein HfO is used₂And/or SiO₂As a dielectric film material.

3. The high laser damage threshold film of claim 2, wherein the film has a film system structure of S/(HL) 10 (AB) 2/Air; wherein S is the substrate of the device, H is HfO₂A dielectric film, L is SiO₂A dielectric film, A is HfO₂Chemical film, B is SiO₂And (5) chemical film.

4. A method for preparing a high laser damage threshold thin film by a physical-chemical method hybrid method is characterized by comprising the following steps: a. SiO plating on optical element substrate by electron beam evaporation and ion beam auxiliary method₂Low refractive index layer, SiO coating₂Plating HfO on the low refractive index layer by electron beam evaporation and ion beam assisted method₂A high refractive index layer; c. preparing HfO by sol-gel method after electron beam evaporation coating₂And SiO₂Dielectric film of SiO₂The colloid is prepared by taking TEOS as an organic alkoxide precursor and mixing TEOS and H₂O，ETOH，NH₃﹒H₂Mixing with O, adding PVP, stirring at room temperature with magnetic stirrer, sealing, aging at room temperature, and adding HfO₂The colloid is prepared from HfOCl₂﹒8H₂Synthesizing HfO by hydrothermal method by using O as raw material₂Sol, then replacing by solvent to obtain HfO₂The glycol methyl ether sol is prepared by a pulling method₂And SiO₂A film.

5. The method for preparing the high laser damage threshold thin film by physical-chemical mixing according to claim 4, wherein the step a is preceded by the following steps: and cleaning the polished optical element substrate, putting the optical element substrate into a vacuum coating machine for heating and air exhaust, and cleaning the surface of the substrate by using a radio frequency ion source.

6. The method for preparing a high laser damage threshold thin film by physical-chemical mixing according to claim 4, wherein the following steps are further included between the steps b and c: and (5) after the electron beam evaporation coating is finished, slowly annealing and aging the optical element substrate in a vacuum chamber for 5 hours.

Technical Field

The invention relates to the technical field of optical films, in particular to a high laser damage threshold film and a preparation method thereof.

Background

Optical device for high power and high energy density laserThe film system and the substrate element are important components of the whole laser system, and the laser damage resistance of the film system and the substrate element is directly related to the output level of the system, which also becomes a key obstacle for preventing the development and wide application of the strong laser system. The intrinsic absorption of the dielectric film material to 1064nm laser is large, so that the laser damage threshold of the optical film is reduced, and the 1064nm high-reflection film is one of the most common optical elements in a laser system, so that the importance of improving the laser damage resistance of the optical film is self-evident. The most fundamental factor for limiting the damage threshold in a 1064nm laser high-reflection film is the energy band gap of the coating material, and the larger the energy band gap is, the higher the threshold is. However, the band gap of the produced film is reduced due to the defects such as impurities or structures introduced in the preparation process, so that the damage threshold is reduced, and the conventional 1064nm high-reflection film is formed by regulating the HfO with the wavelength thickness of 1/4₂And SiO₂The alternating composition is limited by the band gap of the material, and the threshold cannot be further significantly increased. Chemical films generally have damage thresholds that are more than doubled over physical films due to their higher porosity, low heat absorption, and low defect density. However, the chemical plating method has many disadvantages, such as many and complicated influencing factors in the colloid preparation process, and difficult precise control of the thickness and refractive index of the film, which is not suitable for plating the film system structure with too many layers.

Disclosure of Invention

The invention aims to solve the defects of the prior art and provides a 1064nm high-reflectivity film system prepared by mixing a physical-chemical method, and realizes the plating of a high-threshold-value reflective optical film with high reflectivity, good adhesive force and high damage threshold value on an optical element substrate by optimizing a plating process.

In order to achieve the above object, the present invention designs a high laser damage threshold thin film, which comprises a dielectric film with 20 layers prepared by electron beam evaporation; and preparing the outermost 4 film layers with the maximum electric field strength by using a chemical sol-gel method.

The invention also has the following preferable technical scheme:

further, use of HfO₂And/or SiO₂As a dielectric film material.

Furthermore, the film system structure of the film is S/(HL) 10 (AB) 2/Air; wherein S is the substrate of the device, H is HfO₂A dielectric film, L is SiO₂A dielectric film, A is HfO₂Chemical film, B is SiO₂And (5) chemical film.

In another aspect of the present invention, a method for preparing a high laser damage threshold thin film by a physical-chemical hybrid method is also provided, wherein the method comprises the following steps:

a. plating a SiO2 low-refractive-index layer on the optical element substrate by using electron beam evaporation and ion beam auxiliary modes, wherein the SiO2 low-refractive-index layer is plated by adopting an ion source auxiliary process, so as to improve the stress of the film on the fused quartz substrate and obtain larger adhesive force;

b. plating an HfO2 high-refractive-index layer by using electron beam evaporation and ion beam auxiliary modes;

c. preparing a HfO2 dielectric film and a SiO2 dielectric film by using a sol-gel method after electron beam evaporation coating is finished, wherein a SiO2 colloid is prepared by taking TEOS as an organic alkoxide precursor, mixing TEOS, H2O, ETOH, NH3 and H2O, adding PVP, fully stirring at room temperature by using a magnetic stirrer, sealing, and aging at room temperature, a HfO2 colloid is prepared by taking HfOCl2 and 8H2O as raw materials, synthesizing HfO2 sol by a hydrothermal method, then replacing with a solvent to obtain glycol methyl ether sol of HfO2, and preparing HfO2 and SiO2 thin films by using a pulling method.

Further, the step a further comprises the following steps before: and cleaning the polished optical element substrate, putting the optical element substrate into a vacuum coating machine for heating and air exhaust, and cleaning the surface of the substrate by using a radio frequency ion source.

Further, the following steps are also included between steps b and c: and (5) after the electron beam evaporation coating is finished, slowly annealing and aging the optical element substrate in a vacuum chamber for 5 hours.

Advantageous effects of the invention

The high laser damage threshold thin film and the preparation method thereof provided by the invention have the advantages that the method is not limited to the following steps: according to the invention, the optical film with high reflectivity and high damage threshold at 1064nm waveband is prepared by combining the electron beam evaporation and the sol-gel method, and optimizing the structural design of the film system and the film coating process, and the optical film has excellent mechanical property and strong film firmness. The method is simple and easy to implement, has high repeatability, has strong practicability in the whole plating process, can be completed only by vacuum plating equipment and chemical plating, and does not need to add external equipment. The method can effectively solve the plating problem caused by the characteristics of easy diffusion of the chemical film and the like, and the plated film has small stress and strong adhesive force and can be normally and stably used in an optical system. Is suitable for batch production, can meet the market demand of rapid development of optical technology, and has good economic benefit.

Detailed Description

The technical solutions adopted by the present invention are further described below by examples, so that those skilled in the art can better understand the technical solutions adopted by the present invention.

Firstly, the high laser damage threshold film produced by the invention can meet the following technical indexes:

1. the reflectivity is more than 99.5 percent at a 355nm wave band;

2. film firmness: GJB 2485-95;

3. surface smoothness: army mark 40/20;

4. surface type: 1/10 lambda;

5. laser damage threshold: 40J, 10 ns.

The specific preparation process of the film is as follows:

s1, scrubbing the polished optical element substrate by using deionized water and a detergent, and washing the optical element substrate by using the deionized water; then soaking the mixture for 15 minutes by using an acetone solution, taking out the mixture, and washing the mixture by using deionized water again; finally, wiping the mixture by using ethanol and ether mixed solution.

S2, placing the cleaned optical element substrate on a workpiece rack, placing the workpiece rack into a vacuum coating machine, starting air suction after air flow disturbance caused in the workpiece loading process stops (about 5 minutes), and pumping the background vacuum degree to be below 8 x 10 < -4 > Pa. The substrate is heated simultaneously during the pumping process, and the heating temperature is set to 160 ℃.

And S3, after the vacuum degree and the temperature reach the standard, cleaning the surface of the substrate by using a radio frequency ion source to remove dust and micro particle pollutants attached to the surface of the substrate, wherein the ion beam current of the ion source is 190mA, the acceleration voltage is 210V, and the electron beam current is 210 mA.

S4, plating SiO by electron beam evaporation and ion beam auxiliary method₂The deposition rate of the low-refractive-index layer is 3A/s, the ion beam current of an ion source is 300mA, the acceleration voltage is 240V, and the electron beam current is 350 mA. Plating of SiO₂The low refractive index layer adopts an ion source auxiliary process, and aims to improve the stress of the film on the fused quartz substrate and obtain larger adhesion.

S5 plating HfO by electron beam evaporation and ion beam auxiliary method₂The deposition rate of the high-refractive-index layer is 3.5A/s, the ion beam current of the ion source is 310mA, the acceleration voltage is 250V, and the electron beam current is 350 mA.

And S6, after the film coating is finished, slowly annealing the sample in a vacuum chamber and aging for 5 hours, wherein the slow annealing is used for releasing stress after film forming and preventing the film from cracking.

S7, preparing HfO by using sol-gel method after electron beam evaporation coating₂And SiO₂Dielectric film of SiO₂The colloid is prepared by taking TEOS as an organic alkoxide precursor and mixing TEOS and H₂O，ETOH，NH₃﹒H₂Mixing O with volume of 60ml, 8ml, 500ml and 2ml respectively, adding PVP with mass of 0.305g, stirring at room temperature with a magnetic stirrer for more than 3h, sealing, and aging at room temperature for one month. HfO₂The colloid is prepared from HfOCl₂﹒8H₂Synthesizing HfO by hydrothermal method by using O as raw material₂Sol, then replacing by solvent to obtain HfO₂The glycol methyl ether sol is prepared into HfO2 and SiO2 films by a pulling method.

Example 1

In example 1 of the present invention, the size of the plated sample optical element substrate was Φ 50mm × 3 mm. The structure of the membrane system is as follows: S/(HL) 10 (AB) 2/Air, wherein S is the device substrate, H is HfO₂Dielectric film ((thickness 266 nm)), L is SiO₂Dielectric film ((thickness 266 nm)), A is HfO₂Chemical film, B is SiO₂And (5) chemical film. The physical method coating equipment is a domestic vacuum coating machine,and a radio frequency source is configured, and the chemical method coating method comprises dipping and pulling coating.

The preparation method comprises the following steps of S1-S7, wherein the polished quartz substrate is scrubbed by deionized water and a detergent, soaked in an acetone solution for 15 minutes, taken out and wiped clean on a clean bench by using absorbent filament cotton dipped with an ethanol-ether mixed solution (the ratio is 2: 1). Then placing the quartz substrate on a workpiece frame in vacuum coating equipment, standing for five minutes, starting to exhaust, wherein the background vacuum is 8 x 10 < -4 > Pa, and simultaneously heating the substrate in the exhaust process at the heating temperature of 160 ℃. Before the coating starts, an ion source is used for cleaning the substrate, and the ion beam current of the ion source is 190mA, the acceleration voltage is 210V, and the electron beam current is 210 mA. Plating a first layer of SiO₂Depositing at 3A/s rate and ion beam current 300mA, accelerating voltage 240V and electron beam current 350mA, and plating a second layer of HfO₂Meanwhile, the deposition rate is 3.5A/s by means of electron beam evaporation and ion beam assistance, the ion beam current of the ion source is 310mA, the acceleration voltage is 250V, and the electron beam current is 350 mA. In the coating process, the thickness and the speed of the film layer are both monitored by a quartz crystal oscillating piece. After the plating is finished, the alloy is slowly cooled and aged for 5 hours and then taken out. After the electron beam evaporation coating is finished, the chemical method is carried out to prepare a rear 4 layer, wherein SiO₂The colloid is prepared by taking TEOS as an organic alkoxide precursor and mixing TEOS and H₂O，ETOH，NH₃﹒H₂Mixing O with volume of 60ml, 8ml, 500ml and 2ml respectively, adding PVP with mass of 0.305g, stirring at room temperature with a magnetic stirrer for more than 3h, sealing, and aging at room temperature for one month. HfO₂The colloid is prepared from HfOCl₂﹒8H₂Synthesizing HfO by hydrothermal method by using O as raw material₂Sol and then solvent replacement to obtain an ethylene glycol monomethyl ether sol of HfO 2. Preparation of HfO by Czochralski method₂And SiO₂The film was pulled at 200mm/min and 300mm/min, respectively.

The detection of the embodiment 1 is carried out, firstly, the coated sample is tested by an ultraviolet-visible spectrophotometer, the reflectivity at 1064nm is more than 99.5%, and the spectral performance completely meets the use requirement in an optical system. And then, performing film adhesion detection on the prepared sample, covering the surface of the sample film with a Scotch 3M adhesive tape, pulling down the adhesive tape to observe whether the film surface falls off, and detecting the same area for 20 times to ensure that the film is complete and does not fall off.

Compared with the conventional reflective film coating process, the method is characterized in that the optical film which has high reflectivity and high damage threshold at the 1064nm waveband is prepared by combining the electron beam evaporation and the sol-gel method and optimizing the film system structure design and the coating process, and the optical film has excellent mechanical property and strong film firmness.

The key points of the invention are as follows:

combining the advantages of physical method coating and chemical method coating, preparing the multilayer dielectric film by using an evaporation technology to provide high reflectivity for an optical element, realizing the spectral performance of the optical element, and preparing chemical film replacement by using a gel-sol method aiming at the outermost 4 layers with the weakest damage threshold of the dielectric high-reflectivity film, namely the film layer with the largest electric field intensity. The characteristic of high threshold of the chemical film is utilized to improve the laser damage resistance of the optical element, and the dielectric film is responsible for ensuring the whole optical efficiency. Meanwhile, in the coating process, aiming at the characteristics of large absorption and low firmness of the dielectric film, the preparation process is optimized, so that the bonding strength of the metal film layer and the dielectric film layer is high, the film performance is stable, and the surface smoothness is high.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be within the technical scope of the present invention, and the technical solutions and novel concepts according to the present invention should be covered by the scope of the present invention.