CN106903424B - A kind of post-processing approach that optical element mechanical property is improved based on laser blast wave - Google Patents

Abstract

The present invention provides a post-processing method for improving the mechanical properties of optical elements based on laser shock waves. The mechanical properties R ₀ , A ₀ , B ₀ , H ₀ and the ability to resist laser damage F0, G0 as the benchmark, the effects of E ₀ , E _m and ΔE on the mechanical properties R _S , A _S , B _S , _HS and laser damage resistance F _S , G _S of samples after S laser shock wave treatment were respectively obtained; The improvement of performance and laser damage resistance, optimize the initial laser energy E ₀ , energy incremental gradient ΔE and maximum laser energy E _m , when the mechanical properties and laser damage resistance of the thin film element are no longer improved, and meet the requirements of the experimental sample When , the cycle is stopped, and the post-processing of the mechanical properties of the thin film element is completed. The invention realizes the improvement of the mechanical properties of the high-power optical thin-film element, and solves the problem that the mechanical properties of the optical thin-film element, such as adhesive force, film layer bonding force, and residual stress, currently lack effective means to control.

Description

A post-processing method to improve the mechanical properties of optical components based on laser shock waves

technical field

The invention belongs to the technical field of post-processing of optical thin-film elements, and in particular relates to a post-processing method for improving the mechanical properties of optical thin-film elements by using laser shock wave technology.

Background technique

The development of modern high-power laser technology, especially the development of large-aperture systems, puts forward more and more stringent requirements on the performance of optical thin-film components, requiring them to have high optical precision, high mechanical properties, high damage threshold and high-precision surface shape control , will directly affect the function realization of the large-aperture precision optical system and the stability of the long-term operation of the system. There are many factors that affect the performance of optical thin films, including the characteristics of the thin film itself, the preparation process of the thin film, and the laser parameters.

Due to its special multi-layer structure of high and low refractive index materials alternately deposited on the optical glass substrate, especially the most commonly used electron beam evaporation plating optical thin film components in the field of high laser damage threshold thin film research, compared with For bulk materials, there are problems of weak adhesion between the substrate and the film layer, and weak bonding between the film layer and the film layer. However, if the defect-induced laser damage of the thin-film component is accompanied by film peeling, the damage will grow rapidly under the subsequent laser pulse irradiation, resulting in catastrophic damage, which seriously affects the stability of the system operation. At the same time, due to the influence of residual stress and surface shape accuracy caused by the strain mismatch between the materials of the thin film element, it also has a huge impact on the performance of the element and the stability of the system, so the residual stress of the thin film must be strictly controlled. At this stage, the cost of improving the above-mentioned mechanical properties of the film purely by improving the preparation process, optimizing the design of the film system, and developing new coating materials is high. In order to further improve the performance of the film element, researchers at home and abroad have proposed post-processing technology.

Various post-processing technologies, using different process parameters and post-processing methods, can obtain different aspects of film performance improvement for different film materials and structures. The commonly used post-treatment methods include: ion post-treatment, heat treatment and laser pre-treatment. Ion post-treatment is to bombard the film with low-energy ions after the film is prepared to remove the original or adhered weak surface microscopic defects on the film surface and improve the film damage threshold. At present, the most mature technology and the most effective laser pretreatment is to remove the low-threshold nodule defects in the multilayer dielectric film by laser irradiation to improve the laser damage resistance of the film. Heat treatment is also annealing. Although it is mainly used to release the residual stress of the film and improve the surface shape, the repeatability is poor. The heat treatment process parameters required for different materials, different coating parameters, and different types of thin film elements are different, and the degree of improvement is also different. , so there are problems such as difficulty in control in practical applications.

Contents of the invention

The present invention aims at the deficiencies of the above-mentioned prior art, and provides a post-processing method for improving the mechanical properties of optical elements based on laser shock waves.

The present invention is achieved through the following technical solutions:

A post-processing method for improving the mechanical properties of optical elements based on laser shock waves, comprising the following steps:

(1) A batch of optical thin-film elements are prepared by electron beam evaporation; randomly select an optical thin-film element as the sample to be tested, and measure the residual stress R ₀ of the tested sample, the critical adhesion A ₀ of the film layer and the substrate, and the critical adhesion force of the film layer. Interface bonding force B ₀ and hardness H ₀ ;

(2) Select 200 test points on the sample to be tested, and every 20 test points are used as a test group; and 10 different laser energies are selected as the laser energies corresponding to the 10 test groups respectively. The laser energy corresponding to all test points is the same; the number of irradiation pulses for each test point is set to be N ₁ , and the pump laser is used to irradiate the test points on the sample under test with the selected laser energy in sequence, and through online monitoring The system aligns the position where the pump laser irradiates the test sample to detect the occurrence and growth of damage, and obtains the initial damage probability of the test sample under different energies and the damage growth probability under the number of pulses; and through linear fitting Obtain the initial damage threshold F ₀₁ and the damage growth threshold G ₀₁ of the tested sample under the irradiation pulse number N ₁ ;

(3) Reselect a sample to be tested, change the number of irradiation pulses at the test point to N _k , N _k ≠ _{N 1} , and follow the method in step (2) to obtain the Initial lesion threshold F _0k and lesion growth threshold G _0k ;

(4) Repeat step (3) to obtain the initial damage threshold F0 and damage growth threshold G0 under m different pulse irradiation numbers; where, F0={F ₀₁ , F ₀₂ , F ₀₃ ... F _0m }, G0 ={G ₀₁ , G ₀₂ , G ₀₃ ...G _0m }, the number m of pulse irradiation is required to be not less than 200 times of the laser repetition frequency;

(5) Reselect a group of thin film elements from a batch of optical thin film elements produced in step (1), and paste an absorbing layer on the film surface of the group of thin film elements; place a constrained layer on the surface of the absorbing layer to form a laser shock wave post-treatment experimental samples;

⑹ Place the experimental sample on the electric translation stage, and at the same time ensure that the position of the same sample is the same every time; make the online microscope always align with the position of the experimental sample irradiated by the pump laser for real-time detection of the experimental sample, The state of the absorbing and constraining layers;

(7) Set the initial incident laser energy E ₀ , maximum incident laser energy E _m and laser energy incremental gradient ΔE of the pump laser used for laser shock wave processing, and fix the spot size, overlapping ratio and scanning area; require E ₀ and E _m is less than the maximum laser energy that prevents damage to the thin film element when the laser shock wave acts; and mark S as the largest integer less than or equal to (E _m -E ₀ )/ΔE; let i=1;

(8) Let the actual incident laser energy E=E ₀ +ΔE*i;

⑼Using the raster scanning method to scan the sample with a laser shock wave, the microstructure of the surface of the thin film element changes;

⑽ Remove the residual absorbing layer and constrained layer on the surface of the film sample, and spray and ultrasonically clean the film sample to obtain a set of experimental samples after laser shock wave post-treatment;

⑾ Use this group of experimental samples to measure the residual stress R _i after the shock wave post-treatment, the critical adhesion force A _i between the film layer and the substrate, the critical interface bonding force B _i of the film layer, and the hardness H _i , and repeat steps (2) to (4) , to obtain the initial damage threshold F0 _i and damage growth threshold G0 _i under m different pulse irradiation numbers after laser shock wave post-processing;

⑿ Make i=i+1; judge whether i is less than or equal to S, if so, go to step (5), if not, go to step (13);

⒀By irradiating the same area of the tested sample under different energies of the pump laser, the laser shock wave post-processing of the experimental sample with multiple energy gradients was completed, and the mechanical properties of the film element after S laser shock wave post-processing were obtained. , including residual stress R ₁ ～ _RS , critical adhesion force A ₁ ～ _AS , critical interfacial bonding force B ₁ ～B _S , hardness H ₁ ～ _HS and initial damage threshold F0 ₁ under m different pulse irradiation numbers ～F0 _S and damage growth threshold G0 ₁ ～G0 _S ;

⒁Change the initial incident laser energy E ₀ , the maximum incident laser energy E _m and the laser energy incremental gradient ΔE, and repeat steps ⑸ to ⒀; the mechanical properties of the film element R ₀ , A ₀ , B ₀ , Based on H ₀ and laser damage resistance F0 and G0, the mechanical properties R _S , A _S , B _S , H _S and laser damage resistance F _S of samples after S laser shock wave treatment were obtained by E ₀ , E _m and ΔE, respectively. , G _S ; according to the improvement of mechanical properties and laser damage resistance, the initial laser energy E ₀ , energy incremental gradient ΔE and maximum laser energy E _m are optimized. When the mechanical properties and laser damage resistance of thin film elements are not When it is raised again and meets the requirements of the experimental sample, the cycle is stopped to complete the post-processing of the mechanical properties of the thin film element.

The present invention has following beneficial effects:

1. The post-processing method of the present invention realizes the improvement of the mechanical properties of high-power optical thin-film elements, and combines the real-time online adjustment of post-processing process parameters to solve the mechanical properties of optical thin-film elements such as adhesion, film layer bonding force, and residual stress. At present, there is a lack of effective means to control the problem. The present invention can judge technological parameters such as scanning times and laser energy steps according to the mechanical performance requirements and evaluation criteria of the thin film element until the system requirements are met.

2. The post-processing method described in the present invention has no limitation on the type, material, and film deposition parameters of the optical thin film element, such as anti-reflection film, high-reflection film and polarizing film, etc. are all compatible.

3. The post-processing method described in the present invention is not limited by the size of optical elements, and is also applicable to large-diameter optical film elements, which provides a guarantee for the function realization of large-diameter precision optical systems and the stability of the system for a long time, and solves the problem of One of the "bottlenecks" in the development of optical systems in the direction of high energy and high precision.

4. Compared with the traditional heat treatment method, it can only improve the residual stress in the mechanical properties of optical thin film elements, and there are problems such as poor controllability, low repeatability, and unsuitability for large-diameter optical elements. The latter described in the present invention The precision of the processing method is greatly improved, and the controllability and scope of application are greatly improved.

5. After the post-processing method of the present invention is completed, it can be detected online immediately, and the mechanical information such as adhesion force, interface bonding force, hardness, residual stress and the like of the thin film element can be obtained in real time, which is used to detect and evaluate whether the mechanical properties of the thin film element are up to standard.

6. The post-processing method described in the present invention is simple, reliable and widely applicable.

Detailed ways

The present invention will be described in further detail below in combination with specific embodiments.

Example 1:

A post-processing method for improving the mechanical properties of optical elements based on laser shock waves, comprising the following steps:

(1) A 1064nm high-reflection film with a size of φ50×5mm is produced by electron beam evaporation, the residual stress R ₀ of the sample is obtained by a wave surface interferometer, and the critical adhesion A ₀ between the sample film and the substrate is measured by a nano-scratch instrument. Critical interfacial bonding force B ₀ and hardness H ₀ ;

(2) Randomly select 10 laser energy steps F _j (j=1, 2, ..., 10), each laser energy step corresponds to 20 test points, set the number of irradiation pulses N ₁ for each test point, and pass The on-line monitoring system aims at the position where the pump laser irradiates the sample to detect the occurrence and growth of damage, so as to obtain the percentage of the number of damage points to the number of all test points, and the percentage of the number of damage growth points to the number of all test points, that is, to obtain The initial damage probability of the tested sample under different energies and the damage growth probability under the number of pulses; and the initial damage threshold F ₀₁ and the damage growth threshold of the tested sample under the irradiation pulse number N ₁ are obtained by linear fitting G ₀₁ ;

(3) Re-select a sample to be tested from a batch of optical thin film elements made in step (1), change the number of irradiation pulses at the test point to N _k (N _k ≠ N ₁ ), follow the steps in (2) method, obtaining the initial damage threshold F _0k and the damage growth threshold G _0k of the tested sample under the irradiation pulse number N _k ;

(4) Repeat step (3) to obtain the initial damage threshold F0 (F0={F ₀₁ , F ₀₂ , F ₀₃ ... F _0m } and damage growth threshold G0 (G0={ G ₀₁ , G ₀₂ , G ₀₃ ... G _0m }; the number m of pulse irradiation is required to be not less than 200 times the laser repetition frequency, for example, if the repetition frequency is 5Hz, the maximum number of pulses to be tested should be not less than 1000;

(5) Reselect a group of thin film elements from a batch of optical thin film elements produced in step (1), and paste an absorbing layer on the film surface of the thin film element. The absorbing layer is a flexible film made of black paint purchased in the market. The thickness of the absorbing layer is 120 μm, and the thickness fluctuation of the absorbing layer is 8nm, covering the entire sample surface; then a constraining layer is placed on the surface of the absorbing layer. In this embodiment, deionized water is selected as the constraining layer, and deionized water forms a stable thickness on the surface of the absorbing layer A uniform water film of 2.5 mm is used to form an experimental sample after laser shock wave treatment;

⑹ Place the sample to be tested on the electric translation stage, and at the same time, ensure that the position of the same sample is the same every time, so that the post-processing area is the same each time, and the online microscope is always aligned with the pump laser irradiating the sample to be tested. Position, used for real-time detection of the state of the measured sample, absorbing layer and constraining layer during post-processing;

⑺Set the initial incident laser energy E ₀ , maximum incident laser energy E _m and laser energy incremental gradient ΔE of the pump laser used for laser shock wave processing, choose the spot size as 2mm, the overlap rate as 90%, and the scanning area size as 10×10mm, E ₀ and E _m are required to be less than the maximum laser energy that prevents the film element from being damaged when the laser shock wave acts; and mark S as the largest integer less than or equal to (E _m -E ₀ )/ΔE; let i=1;

(8) Let the actual incident laser energy E=E ₀ +ΔE*i;

⑼Using the raster scanning method to scan the sample with a laser shock wave, so that the microstructure of the surface of the thin film element changes;

⑽Remove the residual absorbing layer and constraining layer on the surface of the film sample, and spray and ultrasonically clean the film sample;

⑾After the laser shock wave post-treatment of the thin film sample, the residual stress R _i of the sample is obtained by the wave surface interferometer again, and the critical adhesion force A _i between the sample film and the substrate, the critical interface bonding force B _i and the hardness of the film layer are measured by a nano-scratch instrument H _i , obtain the initial damage threshold F0 _i and damage growth threshold G0 _i under m different pulse irradiation numbers after laser shock wave post-processing;

⑿ Make i=i+1; judge whether i is less than or equal to S, if so, go to step (5), if not, go to step (13);

⒀By irradiating the same area of the tested sample under different energies of the pump laser, the laser shock wave post-processing of the experimental sample with multiple energy gradients was completed, and the mechanical properties of the film element after S laser shock wave post-processing were obtained. , including residual stress R ₁ ～ _RS , critical adhesion force A ₁ ～ _AS , critical interfacial bonding force B ₁ ～B _S , hardness H ₁ ～ _HS and initial damage threshold F0 ₁ under m different pulse irradiation numbers ～F0 _S and damage growth threshold G0 ₁ ～G0 _S ;

⒁Change the initial incident laser energy E ₀ , the maximum incident laser energy E _m and the laser energy incremental gradient ΔE, and repeat steps ⑸ to ⒀; the mechanical properties of the film element R ₀ , A ₀ , B ₀ , Based on H ₀ and laser damage resistance F0 and G0, the mechanical properties R _S , A _S , B _S , H _S and laser damage resistance F _S of samples after S laser shock wave treatment were obtained by E ₀ , E _m and ΔE, respectively. , the influence law of G _S ;

According to the improvement of the mechanical properties and the ability to resist laser damage, the initial laser energy E ₀ , the energy incremental gradient ΔE and the maximum laser energy E _m are optimized. When the requirements are met, stop the cycle and complete the post-treatment of the mechanical properties of the thin film element; at this time, it is considered that the best laser shock wave post-treatment effect is reached, and the corresponding parameters are the optimal laser shock wave post-treatment process parameters; the optimal laser shock wave post-treatment process, Including initial laser energy, energy increasing gradient, maximum laser energy and spot overlapping rate, etc.

Example 2

A post-processing method for improving the mechanical properties of optical elements based on laser shock waves, comprising the following steps:

⑴A 532nm anti-reflection coating with a size of φ30×3mm is produced by electron beam evaporation, and the residual stress R ₀ of the sample is obtained by using a wave surface interferometer, and the critical adhesion A ₀ between the sample film and the substrate is measured by a nano-scratch instrument. Critical interface bonding force B ₀ and hardness H ₀ ; (2) Randomly select 10 laser energy steps F _j (j=1, 2,..., 10), each laser energy step corresponds to 20 test points, set each The number of irradiation pulses N ₁ of the test point is used to detect the occurrence and growth of damage by aligning the position of the pump laser irradiating the sample under test with the online monitoring system, so as to obtain the percentage of the number of damage points to the number of all test points, and obtain the damage growth The percentage of the number of points to the number of all test points, that is, to obtain the initial damage probability of the tested sample under different energy and the damage growth probability under the pulse number; and obtain the tested sample at the irradiation pulse number N ₁ by linear fitting Under the initial damage threshold F ₀₁ and the damage growth threshold G ₀₁ ;

(3) Re-select a sample to be tested from a batch of optical thin film elements made in step (1), change the number of irradiation pulses at the test point to N _k (N _k ≠ N ₁ ), follow the steps in (2) method, obtaining the initial damage threshold F _0k and the damage growth threshold G _0k of the tested sample under the irradiation pulse number N _k ;

(4) Repeat step (3) to obtain the initial damage threshold F0 (F0={F ₀₁ , F ₀₂ , F ₀₃ ... F _0m } and damage growth threshold G0 (G0={ G ₀₁ , G ₀₂ , G ₀₃ ... G _0m }; the number m of pulse irradiation is required to be not less than 200 times the laser repetition frequency, for example, if the repetition frequency is 5Hz, the maximum number of pulses to be tested should be not less than 1000;

(5) Reselect a group of thin film elements from a batch of optical thin film elements produced in step (1), and paste an absorbing layer on the film surface of the thin film element. The absorbing layer is a flexible film made of black paint purchased in the market. The thickness of the absorbing layer is 150 μm, and the thickness fluctuation of the absorbing layer is 8nm, and the area covers the entire sample surface; then, a constrained layer is placed on the surface of the absorbing layer. In this embodiment, deionized water is selected as the constraining layer, and the deionized water forms a stable thickness A uniform water film of 3mm forms an experimental sample after laser shock wave treatment;

⑹ Place the sample to be tested on the electric translation stage, and at the same time, ensure that the position of the same sample is the same every time, so that the post-processing area is the same each time, and the online microscope is always aligned with the pump laser irradiating the sample to be tested. Position, used for real-time detection of the state of the measured sample, absorbing layer and constraining layer during post-processing;

⑺Set the initial incident laser energy E ₀ , maximum incident laser energy E _m and laser energy incremental gradient ΔE of the pump laser used for laser shock wave processing, choose a spot size of 1mm, an overlap rate of 90%, and a scanning area size of 10×10mm, E ₀ and E _m are required to be less than the maximum laser energy that prevents the film element from being damaged when the laser shock wave acts; and mark S as the largest integer less than or equal to (E _m -E ₀ )/ΔE; let i=1;

(8) Let the actual incident laser energy E=E ₀ +ΔE*i;

⑼Using the raster scanning method to scan the sample with a laser shock wave, the microstructure of the surface of the thin film element changes;

⑽Remove the residual absorbing layer and constraining layer on the surface of the film sample, and spray and ultrasonically clean the film sample;

⑾After the laser shock wave post-treatment of the thin film sample, the residual stress R _i of the sample is obtained by the wave surface interferometer again, and the critical adhesion force A _i between the sample film and the substrate, the critical interface bonding force B _i and the hardness of the film layer are measured by a nano-scratch instrument H _i , and repeat steps (2) to (4) to obtain initial damage threshold F0 _i and damage growth threshold G0 _i under m different pulse irradiation numbers after laser shock wave post-treatment;

⑿ Make i=i+1; judge whether i is less than or equal to S, if so, go to step (5), if not, go to step (13);

⒀By irradiating the same area of the tested sample under different energies of the pump laser, the laser shock wave post-processing of the experimental sample with multiple energy gradients was completed, and the mechanical properties of the film element after S laser shock wave post-processing were obtained. , including residual stress R ₁ ～ _RS , critical adhesion force A ₁ ～ _AS , critical interfacial bonding force B ₁ ～B _S , hardness H ₁ ～ _HS and initial damage threshold F0 ₁ under m different pulse irradiation numbers ～F0 _S and damage growth threshold G0 ₁ ～G0 _S ;

⒁Change the initial incident laser energy E ₀ , the maximum incident laser energy E _m and the laser energy incremental gradient ΔE, and repeat steps ⑸ to ⒀; the mechanical properties of the film element R ₀ , A ₀ , B ₀ , Based on H ₀ and laser damage resistance F0 and G0, the mechanical properties R _S , A _S , B _S , H _S and laser damage resistance F _S of samples after S laser shock wave treatment were obtained by E ₀ , E _m and ΔE, respectively. , the influence law of G _S ;

According to the improvement of the mechanical properties and the ability to resist laser damage, the initial laser energy E ₀ , the energy incremental gradient ΔE and the maximum laser energy E _m are optimized. When the requirements are met, stop the cycle and complete the post-treatment of the mechanical properties of the thin film element; at this time, it is considered that the best laser shock wave post-treatment effect is reached, and the corresponding parameters are the optimal laser shock wave post-treatment process parameters; the optimal laser shock wave post-treatment process, Including initial laser energy, energy increasing gradient, maximum laser energy and spot overlapping rate, etc.

⒂Change the coating parameters (deposition rate, deposition temperature, etc.) and repeat the steps ⑴～⒁, and you can also obtain the improvement law of the mechanical properties of the same type of optical thin film elements with different microstructures after laser shock wave post-treatment.

Claims (2)

1. A post-processing method based on laser shock waves to improve the mechanical properties of optical elements, characterized in that, comprising the steps: (1) A batch of optical thin-film elements are prepared by electron beam evaporation; randomly select an optical thin-film element as the sample to be tested, and measure the residual stress R ₀ of the tested sample, the critical adhesion A ₀ of the film layer and the substrate, and the critical adhesion force of the film layer. Interface bonding force B ₀ and hardness H ₀ ; (2) Select 200 test points on the sample to be tested, and every 20 test points are used as a test group; and 10 different laser energies are selected as the laser energies corresponding to the 10 test groups respectively. The laser energy corresponding to all test points is the same; the number of irradiation pulses for each test point is set to be N ₁ , and the pump laser is used to irradiate the test points on the sample under test with the selected laser energy in sequence, and through online monitoring The system aligns the position where the pump laser irradiates the test sample to detect the occurrence and growth of damage, and obtains the initial damage probability of the test sample under different energies and the damage growth probability under the number of pulses; and through linear fitting Obtain the initial damage threshold F ₀₁ and the damage growth threshold G ₀₁ of the tested sample under the irradiation pulse number N ₁ ; (3) Reselect a sample to be tested, change the number of irradiation pulses at the test point to N _k , N _k ≠ _{N 1} , and follow the method in step (2) to obtain the Initial lesion threshold F _0k and lesion growth threshold G _0k ; (4) Repeat step (3) to obtain the initial damage threshold F0 and damage growth threshold G0 under m different pulse irradiation numbers; where, F0={F ₀₁ , F ₀₂ , F ₀₃ ... F _0m }, G0 ={G ₀₁ , G ₀₂ , G ₀₃ ...G _0m }, the number m of pulse irradiation is required to be not less than 200 times of the laser repetition frequency; (5) Reselect a group of thin film elements from a batch of optical thin film elements produced in step (1), and paste an absorbing layer on the film surface of the group of thin film elements; place a constrained layer on the surface of the absorbing layer to form a laser shock wave post-treatment experimental samples; ⑹ Place the experimental sample on the electric translation stage, and at the same time ensure that the position of the same sample is the same every time; make the online microscope always align with the position of the experimental sample irradiated by the pump laser for real-time detection of the experimental sample, The state of the absorbing and constraining layers; (7) Set the initial incident laser energy E ₀ , maximum incident laser energy E _m and laser energy incremental gradient ΔE of the pump laser used for laser shock wave processing, and fix the spot size, overlapping ratio and scanning area; require E ₀ and E _m is less than the maximum laser energy that prevents damage to the thin film element when the laser shock wave acts; and mark S as the largest integer less than or equal to (E _m -E ₀ )/ΔE; let i=1; (8) Let the actual incident laser energy E=E ₀ +ΔE*i; ⑼Using the raster scanning method to scan the sample with a laser shock wave, the microstructure of the surface of the thin film element changes; ⑽ Remove the residual absorbing layer and constrained layer on the surface of the film sample, and spray and ultrasonically clean the film sample to obtain a set of experimental samples after laser shock wave post-treatment; ⑾ Use this group of experimental samples to measure the residual stress R _i after the shock wave post-treatment, the critical adhesion force A _i between the film layer and the substrate, the critical interface bonding force B _i of the film layer, and the hardness H _i , and repeat steps (2) to (4) , to obtain the initial damage threshold F0 _i and damage growth threshold G0 _i under m different pulse irradiation numbers after laser shock wave post-processing; ⑿ Make i=i+1; judge whether i is less than or equal to S, if so, go to step (5), if not, go to step (13); ⒀By irradiating the same area of the tested sample under different energies of the pump laser, the laser shock wave post-processing of the experimental sample with multiple energy gradients was completed, and the mechanical properties of the film element after S laser shock wave post-processing were obtained. , including residual stress R ₁ ～ _RS , critical adhesion force A ₁ ～ _AS , critical interfacial bonding force B ₁ ～B _S , hardness H ₁ ～ _HS and initial damage threshold F0 ₁ under m different pulse irradiation numbers ～F0 _S and damage growth threshold G0 ₁ ～G0 _S ; ⒁Change the initial incident laser energy E ₀ , the maximum incident laser energy E _m and the laser energy incremental gradient ΔE, and repeat steps ⑸ to ⒀; the mechanical properties of the film element R ₀ , A ₀ , B ₀ , Based on H ₀ and laser damage resistance F0 and G0, the mechanical properties R _S , A _S , B _S , H _S and laser damage resistance F _S of samples after S laser shock wave treatment were obtained by E ₀ , E _m and ΔE, respectively. , G _S ; according to the improvement of mechanical properties and laser damage resistance, the initial laser energy E ₀ , energy incremental gradient ΔE and maximum laser energy E _m are optimized. When the mechanical properties and laser damage resistance of thin film elements are not When it is raised again and meets the requirements of the experimental sample, the cycle is stopped to complete the post-processing of the mechanical properties of the thin film element. 2. The post-processing method for improving the mechanical properties of optical elements based on laser shock waves according to claim 1, characterized in that, after the step (14), it can also include: changing the coating parameters in the step (1), repeating steps ⑴～⒁ , to obtain the improvement rule of laser shock wave post-processing on the mechanical properties of the same type of optical thin film elements with different microstructures.