A surface treatment process for improving the laser damage threshold of fused quartz components

Abstract

The present invention provides a surface treatment process for improving the laser damage threshold of fused silica components. Through high-temperature annealing treatment, the subsurface defect layer is reduced and healed to varying degrees, and then H2O2 shallow etching is used to remove the subsurface defect layer with a small amount of material removal, so as to achieve the purpose of improving the laser damage threshold. The present invention provides a more economical, clean, environmentally friendly and safe surface treatment technology for fused silica components, which can effectively improve the laser damage threshold of fused silica optical components and provide an important technical guarantee for the engineering application of high-quality fused silica components in the field of laser inertial confinement fusion.

Description

Technical Field

[0001] The invention belongs to the field of optical element processing, and in particular relates to a surface treatment process for improving the damage threshold of a fused quartz element. Background Art

[0002] Fused quartz components are widely used to manufacture various high-quality optical components due to their excellent optical and mechanical properties, especially in the field of laser inertial confinement fusion, and have become the main force for exploring and developing controlled nuclear fusion technology. However, due to various surface defects such as scratches and pits introduced on the surface of fused quartz optical components during the early manufacturing processes such as grinding and polishing, laser damage will occur under the action of high-power laser irradiation and increase geometrically with the increase of irradiation time and laser intensity, which seriously weakens the load capacity of optical components. At the same time, the presence of these surface defects will reduce the mechanical strength and durability of optical components, seriously shorten the service life, and greatly increase the maintenance cost of optical systems.

[0003] At present, people have explored many ways to remove or suppress the surface defects of fused quartz components. First, people continue to improve and enhance the preliminary manufacturing process based on grinding and polishing, and try to reduce and minimize the preliminary manufacturing defects to the minimum. They have also developed precision polishing technologies such as mechanical chemical polishing, magnetorheological polishing, and magnetic field-assisted polishing. Although these emerging technologies can reduce the surface defects of fused quartz to the micron level without expanding sub-surface defects, it has been confirmed that these methods have no significant effect on improving the laser damage threshold of fused quartz components. At the same time, in order to reduce the surface defects of fused silica components to a minimum, people have developed a series of surface removal technologies based on etching. Among them, dry etching technology (such as ion beam etching) removes at the atomic level by particle bombardment, which can control the morphology and easily obtain a smooth surface. It has a significant effect on removing the surface defect layer, but it will also leave chemical structural defects (such as NBO, etc.) on the surface of the component and material densification, such as "Reaction ion etching process for improving laser damage resistance of fused silica optical surface" (see Optics express, 2016, 24 (1): 199-211). In addition to introducing chemical defects, chemical wet etching (such as HF dynamic chemical etching) will also expose and expand structural defects (such as pits, scratches and cracks, etc.), such as "Effect of HF etching on the surface quality and laser-induced damage of fused silica" (see Optics & Laser Technology, 2012, 44 (4): 1039-1042).Some combined treatment methods that couple multiple technologies, such as the combination of magnetorheological polishing and HF etching, the combined treatment technology of CHF3 / Ar reactive ion etching (RIE) and HF dynamic chemical etching, etc., can achieve better results in controlling surface defects of optical components compared with a single technology, such as "Combination of reaction ion etching and dynamic chemical etching for improving laser damage resistance of fused silica optical surfaces" (see Optics Letters, 2016, 41(19): 4464-4467). However, all of them use HF etching as the final treatment link. HF is a reagent that is extremely harmful to the environment and human body, and its recycling and recovery are difficult, so it cannot be used as an ideal etching solvent.

[0004] In summary, although the current surface treatment methods for fused quartz components have good effects in removing surface defects and improving laser damage resistance, they all have certain drawbacks or shortcomings that hinder their further development and application. Therefore, providing a more economical, clean, environmentally friendly and safe surface treatment technology is an important engineering and technical problem that needs to be solved urgently. Summary of the invention

[0005] The present invention is proposed to solve the deficiencies of the above-mentioned prior art. The currently existing surface treatment processes for fused quartz components with good effects all have the step of removing the sub-surface defect layer by HF etching as the last step. This method not only leads to a significant deterioration of the surface quality of the optical component, but also causes a series of deep-seated engineering problems, including poor recycling rate, harm to human health, and difficulty in environmental protection treatment.

[0006] The present invention provides a more economical, clean, environmentally friendly and safe surface treatment process for improving the laser damage threshold of fused quartz components. The present invention can effectively and controllably remove surface defects of fused quartz components through the combination of thermal annealing and H2O2 etching, thereby improving its ability to resist laser damage.

[0007] In order to achieve the purpose of the present invention, the following technical solution is provided: a surface treatment process for improving the laser damage threshold of a fused quartz component, comprising the following steps:

[0008] (1) Pretreatment

[0009] Pre-treat the fused quartz to remove dust, particles and other impurities remaining on the surface of the fused quartz components during the previous processing and storage process, which may affect the effect of subsequent processing;

[0010] (2) High temperature annealing

[0011] The pre-treated fused quartz element is subjected to high temperature annealing treatment to shrink and heal sub-surface defects, so that the sub-surface defect layer becomes shallower, and the subsequent required etching depth is reduced. By removing less material, the etching efficiency is greatly improved, and the amount of subsequent etching solvent is reduced;

[0012] (3) Re-cleaning

[0013] Re-clean the annealed fused quartz component to remove dust, particles and other impurities adsorbed on the surface of the fused quartz component from the annealing chamber atmosphere, as well as new impurities converted from impurities above a certain level under high temperature conditions, to ensure the subsequent etching effect;

[0014] (4) H2O2 solution etching

[0015] The fused quartz component that has been re-cleaned is etched and placed in a H2O2 solution for sealing and etching, so as to remove shallow surface defects of the fused quartz component in combination with high-temperature annealing. It should be noted that the use of H2O2 etching to remove the defective layer on the surface of the component will not introduce other impurities or pollution compared to HF etching;

[0016] Preferably, the pretreatment is to use anhydrous ethanol and deionized water to ultrasonically clean the fused quartz element in sequence, the frequency of the ultrasonic cleaning is 20kHz to 135kHz, and the use of ultrasonic assisted cleaning at this frequency can effectively improve the cleaning effect, and then rinse with deionized water to further clean the surface of the fused quartz element, and finally blow dry the surface of the fused quartz element with dry nitrogen to prevent the residual moisture on the surface of the element from producing microchemical reactions with the glass surface during subsequent high-temperature annealing to produce defects, and use nitrogen for rapid drying to prevent the surface water of the fused quartz element from absorbing particles, impurities, etc. in the air due to adsorption.

[0017] Preferably, the high temperature annealing temperature is 400° C. to 1100° C., the annealing time is 2 to 12 hours, and the atmosphere in the annealing chamber is nitrogen.

[0018] Preferably, the re-cleaning is to use anhydrous ethanol and deionized water for ultrasonic cleaning in sequence, rinse the surface of the fused quartz element with deionized water, and use dry nitrogen to blow dry for standby use; the frequency of the ultrasonic cleaning of the re-cleaning is 20kHz to 135kHz.

[0019] Preferably, ultrasonic wave and temperature raising auxiliary treatment are used during the H2O2 solution etching of the fused quartz element to accelerate the etching rate;

[0020] More preferably, the concentration of hydrogen peroxide in the H2O2 solution is 3wt% to 30wt%, the etching treatment time is 1h to 12h, the reaction temperature of the etching treatment is 20°C to 100°C, and the frequency of ultrasonic assisted etching is 20kHz to 135kHz.

[0021] The present invention also provides a fused quartz element, which is prepared by the surface treatment process for improving the laser damage threshold of the fused quartz element.

[0022] The surface treatment process for improving the laser damage threshold of fused quartz components proposed by the present invention has at least the following beneficial effects:

[0023] The present invention shrinks and heals subsurface defects by annealing, making the subsurface defect layer shallower, reducing the subsequent required etching depth, greatly improving the etching efficiency by removing less material, and reducing the amount of subsequent etching solvent. The latter step innovatively proposes to use H2O2 etching to remove the defect layer on the surface of the component, which is more economical, clean, environmentally friendly and safer than HF etching, and will not introduce other impurities or pollution.

[0024] The present invention provides a more economical, clean, environmentally friendly and safe fused quartz component surface treatment technology, which can effectively improve the laser damage threshold of fused quartz optical components and provide important technical guarantee for the engineering application of high-quality fused quartz components in the field of laser inertial nuclear fusion.

[0025] Other advantages, objectives and features of the present invention will be reflected in part from the following description, and in part will be understood by those skilled in the art through study and practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of a surface treatment process for improving the laser damage threshold of a fused quartz component provided by the present invention;

[0027] Figure 2 This is an atomic force microscope (AFM) three-dimensional morphology image of the surface of a fused quartz component without any treatment;

[0028] Figure 3 A three-dimensional atomic force microscope (AFM) morphology image of the surface of the fused quartz element provided in Example 1;

[0029] Figure 4 A three-dimensional atomic force microscope (AFM) morphology image of the surface of the fused quartz element provided in Example 2;

[0030] Figure 5 A three-dimensional atomic force microscope (AFM) morphology image of the surface of the fused quartz element provided in Example 3;

[0031] Figure 6Atomic force microscope (AFM) three-dimensional morphology image of the surface of the fused quartz element provided in this comparative example 1;

[0032] Figure 7 Atomic force microscope (AFM) three-dimensional morphology image of the surface of the fused quartz element provided in this comparative example 2; DETAILED DESCRIPTION

[0033] The specific scheme proposed by the present invention is described in more detail with reference to several specific embodiments below.

[0034] The reagents and instruments used in the examples and comparative examples of the present invention are all conventional products that can be purchased commercially.

[0035] Example 1

[0036] A conventionally polished fused quartz element was taken, the size of which was 50 mm×50 mm×5 mm and the surface roughness was 0.54 nm.

[0037] 1. Preprocessing:

[0038] The fused quartz component was ultrasonically cleaned at a frequency of 45 kHz for 5 min using anhydrous ethanol and deionized water in sequence, and the surface of the fused quartz component was rinsed with deionized water for 2 min. Finally, the surface of the component was blown dry with dry nitrogen for standby use.

[0039] 2. High temperature annealing:

[0040] The pretreated fused quartz element was placed in a quartz inner tube of a high-temperature annealing furnace, and nitrogen was filled into the quartz inner tube to seal it, and annealed at 500°C for 4 hours.

[0041] 3. Re-cleaning:

[0042] After high-temperature annealing, the fused quartz component was ultrasonically cleaned with anhydrous ethanol and deionized water at a frequency of 60kHz for 7 minutes, and then the surface of the fused quartz component was rinsed with deionized water for 3 minutes. Finally, the surface of the component was blown dry with dry nitrogen for standby use.

[0043] 4. H2O2 solution etching:

[0044] The cleaned fused quartz component was placed in a 10% mass fraction H2O2 solution for sealing and etching for 7 hours, during which it was assisted by ultrasonic water bath heating with an ultrasonic frequency of 28 kHz and a water bath temperature of 40°C.

[0045] After 7 hours, the fused quartz component was taken out and cleaned with anhydrous ethanol and deionized water in turn to remove the residual H2O2 solution on the surface of the fused quartz component, and then dried with dry nitrogen for standby use.

[0046] The surface roughness of the fused quartz element after treatment in this embodiment was measured to be 0.43 nm. Figure 3 .

[0047] Example 2

[0048] A conventionally polished fused quartz element was taken, the size of which was 50 mm×50 mm×5 mm and the surface roughness was 0.54 nm.

[0049] 1. Preprocessing:

[0050] The fused quartz component was ultrasonically cleaned at a frequency of 45 kHz for 8 minutes using anhydrous ethanol and deionized water in sequence, and the surface of the fused quartz component was rinsed with deionized water for 3 minutes. Finally, the surface of the component was blown dry with dry nitrogen for later use.

[0051] 2. High temperature annealing:

[0052] The pretreated fused quartz element was placed in a quartz inner tube of a high-temperature annealing furnace, and nitrogen was filled into the quartz inner tube to seal it, and annealed at 800°C for 6 hours.

[0053] 3. Re-cleaning:

[0054] After high-temperature annealing, the fused quartz component was ultrasonically cleaned with anhydrous ethanol and deionized water at a frequency of 100 kHz for 8 minutes, and then the surface of the fused quartz component was rinsed with deionized water for 3 minutes. Finally, the surface of the component was blown dry with dry nitrogen for standby use.

[0055] 4. H2O2 solution etching:

[0056] The cleaned fused quartz component was placed in a 20% mass fraction H2O2 solution for sealing and etching for 8 hours, during which it was assisted by ultrasonic water bath heating with an ultrasonic frequency of 80 kHz and a water bath temperature of 60°C.

[0057] After 8 hours, the fused quartz component was taken out and cleaned with anhydrous ethanol and deionized water in turn to remove the residual H2O2 solution on the surface of the fused quartz component, and then dried with dry nitrogen for standby use.

[0058] The surface roughness of the fused quartz element after treatment in this embodiment was measured to be 0.38 nm. Figure 4 .

[0059] Example 3

[0060] A conventionally polished fused quartz element was taken, the size of which was 50 mm×50 mm×5 mm and the surface roughness was 0.54 nm.

[0061] 1. Preprocessing:

[0062] The fused quartz component was ultrasonically cleaned with anhydrous ethanol and deionized water at a frequency of 45 kHz for 10 minutes, and then the surface of the fused quartz component was rinsed with deionized water for 3 minutes. Finally, the surface of the component was blown dry with dry nitrogen for standby use.

[0063] 2. High temperature annealing:

[0064] The pretreated fused quartz element was placed in a quartz inner tube of a high-temperature annealing furnace, and nitrogen was filled into the quartz inner tube to seal it, and annealed at a temperature of 1000° C. for 10 hours.

[0065] 3. Re-cleaning:

[0066] After high-temperature annealing, the fused quartz component was ultrasonically cleaned with anhydrous ethanol and deionized water at a frequency of 135kHz for 9 minutes, and then the surface of the fused quartz component was rinsed with deionized water for 3 minutes. Finally, the surface of the component was blown dry with dry nitrogen for standby use.

[0067] 4. H2O2 solution etching:

[0068] The cleaned fused quartz component was placed in a 25% mass fraction H2O2 solution for sealing and etching for 9 hours, during which it was assisted by ultrasonic water bath heating with an ultrasonic frequency of 100 kHz and a water bath temperature of 100°C.

[0069] After 9 hours, the fused quartz component was taken out and cleaned with anhydrous ethanol and deionized water in turn to remove the residual H2O2 solution on the surface of the fused quartz component, and then dried with dry nitrogen for later use.

[0070] The surface roughness of the fused quartz element after treatment in this embodiment was measured to be 0.32 nm. Figure 5 .

[0071] Comparative Example 1

[0072] The other conditions are the same as those in Example 3, except that no annealing treatment was performed in this comparative example. The surface roughness of the fused quartz element after the treatment in this comparative example was measured to be 0.47 nm. Figure 6 .

[0073] Comparative Example 2

[0074] The other conditions are the same as those in Example 3, except that the H2O2 solution etching treatment was not performed in this comparative example. The surface roughness of the fused quartz element after the treatment in this comparative example was measured to be 0.49 nm. Figure 7 .

[0075] According to the "Test Method for Laser Damage Threshold of Optical Surface" (GB / T 16601-1996), the fused quartz components obtained by the treatment of Examples 1 to 3 and Comparative Examples 1 to 2 and the fused quartz components without any treatment (AFM showed Figure 2) of the fused quartz component surface, the results are shown in Table 1 below:

[0076] Table 1

[0077]

[0078] The results show that by combining high temperature annealing with H2O2 solution etching, the sub-surface defects can be shrunk and healed by annealing, making the sub-surface defect layer shallower. Then, H2O2 solution can be used instead of HF etching to effectively remove sub-surface defects and improve the laser damage threshold of fused quartz components.

[0079] The combination of high temperature annealing and H2O2 solution etching in the present invention is not just a simple overlap of effects, but a synergistic effect. Reversing or changing the order cannot achieve the same or similar technical effects as the present invention. The reason is that high temperature annealing can shrink and heal sub-surface defects, making the sub-surface defect layer shallower, but it will also introduce annealing residual pollutants on the surface of the fused quartz component. The present invention removes the sub-surface defect layer by etching with H2O2 solution, and also effectively removes the annealing residual pollutants; and, traditional HF solution etching is prone to residual inorganic salt deposition or other impurities on the surface of the fused quartz component, resulting in a decrease in the laser damage threshold of the surface of the fused quartz component, and subsequent processes such as laser or ion beam need to be introduced to remove the inorganic salt deposition, while the present invention avoids the introduction of inorganic salt deposition through H2O2 solution etching, thereby improving the laser damage threshold of the fused quartz component; in addition, HF acid is harmful to the environment and human body and the waste liquid is difficult to handle, while H2O2 solution is decomposed into oxygen and water after etching, which is clean and environmentally friendly; therefore, the method of the present invention is not a simple patchwork of prior art, but is obtained through a lot of creative labor.

[0080] The embodiments described above are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the aforementioned embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention.

Claims

1. A surface treatment process for improving the laser damage threshold of a fused quartz component, comprising the following steps: S1: high temperature annealing treatment of the fused quartz element; S2: After ultrasonically cleaning the fused quartz component treated in S1 with anhydrous ethanol and deionized water in turn, the surface of the fused quartz component is rinsed with deionized water, and then dried with dry nitrogen for later use; S3: Perform H2O2 etching on the fused quartz component treated by S2, place the fused quartz component treated by S2 in a H2O2 solution for sealing and etching, and use ultrasonic and temperature-raising assisted etching during the process; In S1, the temperature of high temperature annealing is 400°C to 1100°C; the duration of high temperature annealing is 2 to 12 hours; the atmosphere in the annealing chamber is any one of dry air and nitrogen; In S3, the concentration of hydrogen peroxide in the H2O2 solution is 3wt%~30wt%; the H2O2 etching treatment using the fused quartz element lasts for 1h~12h; the frequency of ultrasonic assistance during the H2O2 etching process is 20 kHz~135kHz, and the auxiliary temperature is raised to 20℃~100℃.

2. The surface treatment process for improving the laser damage threshold of fused silica components according to claim 1, characterized in that: Before the S1 high temperature annealing treatment, the fused silica component is pre-treated.

3. The surface treatment process for improving the laser damage threshold of fused quartz components according to claim 2, characterized in that: The pretreatment is to use anhydrous ethanol and deionized water to ultrasonically clean the fused quartz element in sequence, then rinse the surface of the fused quartz element with deionized water, and finally blow dry the surface of the fused quartz element with dry nitrogen for standby use.

4. The surface treatment process for improving the laser damage threshold of fused silica components according to claim 3, characterized in that: The ultrasonic cleaning frequency of the pretreatment is 20kHz~135kHz.

5. The surface treatment process for improving the laser damage threshold of fused silica components according to claim 1, characterized in that: In S2, the frequency of ultrasonic cleaning is 20kHz ~ 135kHz.

6. A fused quartz component, characterized in that: The method is prepared by the surface treatment process for improving the laser damage threshold of the fused quartz component as described in any one of claims 1 to 5.

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