阅读说明：本技术 一种提高光学薄膜元件抗激光损伤能力的方法 (Method for improving laser damage resistance of optical film element ) 是由 刘文文 蒲唐阳 梁龙 曹宇 张健 朱德华 于 2020-05-13 设计创作，主要内容包括：本发明提供了一种提高光学薄膜元件抗激光损伤能力的方法,包括：首先获得光学薄膜元件的功能性损伤阈值；之后进行光学薄膜元件的覆层处理和激光诱导等离子体冲击后处理：获得经过不同扫描参数激光诱导离子体后处理作用后的所有薄膜元件功能性损伤阈值；选择其中最大的功能性损伤阈值作为光学薄膜元件的最优功能性损伤阈值,其对应的脉宽和扫描参数为最优参数；采用所述最优参数对光学薄膜元件进行激光诱导等离子体后处理来提高光学薄膜元件抗激光损伤能力。本发明可同时降低薄膜中的结构型和吸收型缺陷的缺陷密度,又可改善薄膜界面间的结合力等力学性能,解决了目前现有后处理技术只对少部分薄膜元件类型有效且提升效果也有限的难题。(The invention provides a method for improving the laser damage resistance of an optical thin film element, which comprises the following steps: firstly, obtaining a functional damage threshold value of the optical thin film element; then, coating treatment and laser-induced plasma impact post-treatment of the optical thin film element are carried out: obtaining functional damage thresholds of all thin film elements after laser-induced plasma post-treatment with different scanning parameters; selecting the maximum functional damage threshold value as the optimal functional damage threshold value of the optical thin film element, wherein the corresponding pulse width and scanning parameters are the optimal parameters; and performing laser-induced plasma post-treatment on the optical thin film element by adopting the optimal parameters to improve the laser damage resistance of the optical thin film element. The invention can simultaneously reduce the defect density of structural defects and absorption defects in the film, can also improve the mechanical properties such as the binding force between film interfaces and the like, and solves the problems that the existing post-treatment technology is only effective to a small number of film element types and has limited improvement effect.)

1. A method for improving the laser damage resistance of an optical film element is characterized by comprising the following steps:

(1) plating a batch of optical thin film elements as samples, and carrying out spraying and ultrasonic cleaning;

(2) obtaining a functional damage threshold of the optical thin film element;

the specific method comprises the following steps:

(2.1) randomly selecting an optical thin film element as a tested sample, fixing the tested sample on an electric translation table, controlling the two-dimensional movement of the tested sample by the electric translation table, and aligning the position of the pump laser irradiated tested sample by an online monitoring system for diagnosing the occurrence of damage and accurately positioning;

(2.2) scanning the surface of the sample to be measured by 1cm in a raster scanning mode²Region of (a), setting a maximum energy flow step E_mAnd an initial energy flow step E₀And is lifted at an interval of delta E, wherein the delta E is 1-10J/cm²(ii) a At the same time E₀And Δ E is taken to be such that (E)_m-E₀) The value of/. DELTA.E is [10,12 ]]The largest integer within the interval; scanning according to the sequence of energy flow steps from low to high, scanning the next step after scanning one energy flow step, pausing the scanning of the next step after scanning the complete test area of the energy flow step once the energy flow step is damaged in the scanning process, and entering the step (2.3) to judge the size of the damaged point if the number of pit-breaking points of the energy flow step is not more than 10; otherwise, stopping the test, wherein the laser energy density corresponding to the previous energy flow step is the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

(2.3) moving the tested sample, sequentially positioning all damage pits appearing in the scanning process, firstly judging whether the sizes of all the damage pits exceed 100um, and if the sizes of the damage pits do not exceed 100um, entering the step (2.4) to carry out growth test on the damage pits;

if the size of one damaged point exceeds 100um, stopping the test, and the laser energy density corresponding to the previous energy flow step is the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

(2.4) irradiating N pulses on the damage point with the size not exceeding 100um to generate the damage energy flow step, wherein N is 100, 200, 300.. 10000, if the damage pit does not grow after N pulses, the energy flow lifting delta E continues to irradiate N pulses until the growth phenomenon occurs or the energy E is reached_mIf damage growth occurs in the growth test, stopping the test, and determining the laser energy density corresponding to the maximum energy flow step without growth as the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

if the energy E is reached_mMoving the tested sample to the starting point of the test area without increasing all the damage points, turning to the step (2.2), and continuing the scan test of energy flow lifting until the energy flow lifting reaches 1cm²The area has more than 10 damaged pits or the damaged pits are larger than 100 mu m or any damaged pit grows under the action of subsequent laser, and the laser energy density corresponding to the previous energy flow step at the moment is the functional damage threshold F of the tested sample_th0；

(3) Carrying out coating treatment of the optical film element: covering a layer of absorbing material on the surfaces of other optical thin film elements in the same batch to generate high-temperature high-pressure plasma; the absorbing material is black paint or a flexible film which can ensure 100 percent of incident laser energy to be completely absorbed, the thickness of the absorbing material is 0.5 mm-1.0 mm, meanwhile, the thickness uniformity deviation of each part of the absorbing layer is ensured to be less than 10 mu m, the absorbing layer covers the surface of the whole optical film element, and the surface of the absorbing material is covered with a restraint layer; further obtaining a plurality of samples subjected to coating treatment;

(4) carrying out laser-induced plasma shock post-treatment on the optical thin film element:

firstly, determining the value combination of the scanning parameters, whereinThe scanning parameters include incident laser energy, scanning times, spot diameter, overlap ratio, low repetition rate and high repetition rate, wherein the incident laser energy is at the minimum energy and E of the laser output_m5 numerical values are taken at equal intervals, the scanning frequency is 1-5 times, the diameter of a light spot is 100 micrometers, 500 micrometers, 1mm, 1.5mm or 2mm, the lap joint rate is 30%, 50%, 70% or 90%, the low repetition frequency is any one numerical value in the range of 1-10 Hz, and the high repetition frequency is any one numerical value in the range of a few KHz-a few tens KHz; each group of scanning parameters corresponds to a sample subjected to coating treatment;

then selecting a group of scanning parameters, selecting a sample subjected to coating treatment, placing the sample on a motor-driven translation table, and selecting 1cm from the center of the sample²The area adopts a nanosecond laser to carry out raster scanning according to the selected scanning parameters, so that the energy of the incident laser is always ensured to be less than the maximum laser energy E which can prevent the thin film element from being damaged_mThe online microscope is always aligned to the position of the pump laser irradiation detected sample to detect the states of the detected sample, the absorption material and the restraint layer in the laser irradiation process in real time; removing the restraint layer covered on the surface of the sample, removing residual absorbing materials on the surface by using acetone and ethanol solution, and further carrying out spraying and ultrasonic cleaning on the sample to finish laser-induced plasma impact post-treatment of an optical thin film element;

finishing the post-treatment process of the laser-induced plasma of the optical thin film element under all scanning parameter combinations according to the method;

(5) obtaining the functional damage threshold F of all thin film elements after the post-treatment of the laser-induced plasma with different scanning parameters according to the method in the step (2)_thi-ns；

(6) Replacing the nanosecond laser in the step (4) with a picosecond laser or a femtosecond laser, repeating the steps (4) to (5), and respectively obtaining the functional damage threshold F of the optical thin film element after the post-treatment of the laser-induced plasma of different scanning parameters by the picosecond laser and the femtosecond laser_thi-psAnd F_thi-fs；

(7) Comparison of the optical films not post-treated in step (2)Threshold value of functional damage F of element_th0And (5) after nanosecond laser-induced plasma impact treatment, performing functional damage threshold F on the thin film element_thi-nsAnd (6) a functional damage threshold F of the thin film element after picosecond and femtosecond laser-induced plasma post-treatment_thi-psAnd F_thi-fsSelecting the maximum functional damage threshold value as the optimal functional damage threshold value of the optical thin film element, wherein the corresponding pulse width and scanning parameters are the optimal parameters;

(8) and performing laser-induced plasma post-treatment on the optical thin film element by adopting the optimal parameters to improve the laser damage resistance of the optical thin film element.

Technical Field

The invention belongs to the field of optical film pretreatment, and particularly relates to an optical film element based on laser-induced plasma action, and a method for improving the laser damage resistance of the optical film element under single-pulse and multi-pulse nanosecond laser irradiation.

Background

Among the optical elements of the laser device, the optical thin film element controls the transmission of the laser beam, which may cause laser damage under high energy flux density irradiation, and even cause chain reaction when the damage is serious, resulting in damage to other optical elements, and further causing the breakdown of the whole laser system. The development of modern high-power laser technology puts more and more demanding requirements on the performance of optical thin film elements, such as requirements on high optical precision, high mechanical property, high-precision surface shape control and the like, and particularly the laser damage resistance of the elements directly influences the function realization of a precision optical system and the stability of the system in long-time operation.

Under the irradiation of nanosecond pulse width laser, main factors influencing the single-pulse laser irradiation functional damage threshold and the multi-pulse laser irradiation functional damage growth threshold of the thin film element are defect-induced thermal destruction processes, and besides the defect serving as a damage source, the defect is easier to break through the constraint and generate damage due to weaker mechanical properties between films. Therefore, the process of improving the laser damage resistance of the optical film element is the process of reducing the defects in the film and improving the mechanical property of the film. To address this problem, current research efforts fall into two main categories. One is to reduce the hole density at the alternate discrete interface of two coating materials and the nodule defect density in the film layer and improve the laser damage resistance of the film element by starting from the film system design and the film layer deposition process. The other type starts from the film element post-processing technology, which comprises laser pretreatment, heat treatment and ion post-processing, and can obtain film performance improvement in different aspects by adopting different process parameters and post-processing modes according to different film system materials and structures. However, the work of film system design, film deposition process and film post-processing technology is limited by the current technical means, and it is difficult to simultaneously reduce the defects and improve the mechanical properties of the film for the optical thin film element deposited by electron beam evaporation, and especially, the work can be applied to different types of thin film elements.

When the laser energy density exceeds the ionization threshold of the irradiated material, a high temperature, high pressure plasma is formed, and once the plasma is formed, a lower laser energy density may maintain it. With the further deepened understanding of the mechanism and conditions of laser-induced plasma formation, the application of laser-induced plasma in various research fields, such as laser-induced plasma etching, laser-induced plasma deposition, laser-induced plasma spectroscopy, laser shock peening, etc., is continuously developed.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for improving the laser damage resistance of an optical film element.

The invention is realized by the following technical scheme:

a method for improving the laser damage resistance of an optical thin film element comprises the following steps:

(1) plating a batch of optical thin film elements as samples, and carrying out spraying and ultrasonic cleaning;

(2) obtaining a functional damage threshold of the optical thin film element;

the specific method comprises the following steps:

(2.1) randomly selecting an optical thin film element as a tested sample, fixing the tested sample on an electric translation table, controlling the two-dimensional movement of the tested sample by the electric translation table, and aligning the position of the pump laser irradiated tested sample by an online monitoring system for diagnosing the occurrence of damage and accurately positioning;

(2.2) scanning the surface of the sample to be measured by 1cm in a raster scanning mode²Region of (a), setting a maximum energy flow step E_mAnd an initial energy flow step E₀And is lifted at an interval of delta E, wherein the delta E is 1-10J/cm²(ii) a At the same time E₀And Δ E is taken to be such that (E)_m-E₀) The value of/. DELTA.E is [10,12 ]]The largest integer within the interval; and scanning according to the sequence of energy flow steps from low to high, one energy flowAfter the step is scanned, scanning of the next step is carried out, once the step is damaged in the scanning process, the scanning of the next step is suspended after the energy flow step scans the complete test area, and if the number of broken pits of the energy flow step is not more than 10, the step (2.3) is carried out to judge the size of the damaged point; otherwise, stopping the test, wherein the laser energy density corresponding to the previous energy flow step is the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

(2.3) moving the tested sample, sequentially positioning all damage pits appearing in the scanning process, firstly judging whether the sizes of all the damage pits exceed 100um, and if the sizes of the damage pits do not exceed 100um, entering the step (2.4) to carry out growth test on the damage pits;

if the size of one damaged point exceeds 100um, stopping the test, and the laser energy density corresponding to the previous energy flow step is the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

(2.4) irradiating N pulses on the damage point with the size not exceeding 100um to generate the damage energy flow step, wherein N is 100, 200, 300.. 10000, if the damage pit does not grow after N pulses, the energy flow lifting delta E continues to irradiate N pulses until the growth phenomenon occurs or the energy E is reached_mIf damage growth occurs in the growth test, stopping the test, and determining the laser energy density corresponding to the maximum energy flow step without growth as the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

if the energy E is reached_mMoving the tested sample to the starting point of the test area without increasing all the damage points, turning to the step (2.2), and continuing the scan test of energy flow lifting until the energy flow lifting reaches 1cm²The area has more than 10 damaged pits or the damaged pits are larger than 100 mu m or any damaged pit grows under the action of subsequent laser, and the laser energy density corresponding to the previous energy flow step at the moment is the functional damage threshold F of the tested sample_th0；

(3) Carrying out coating treatment of the optical film element: covering a layer of absorbing material on the surfaces of other optical thin film elements in the same batch to generate high-temperature high-pressure plasma; the absorbing material is black paint or a flexible film which can ensure 100 percent of incident laser energy to be completely absorbed, the thickness of the absorbing material is 0.5 mm-1.0 mm, meanwhile, the thickness uniformity deviation of each part of the absorbing layer is ensured to be less than 10 mu m, the absorbing layer covers the surface of the whole optical film element, and the surface of the absorbing material is covered with a restraint layer; further obtaining a plurality of samples subjected to coating treatment;

(4) carrying out laser-induced plasma shock post-treatment on the optical thin film element:

firstly, determining a value combination of scanning parameters, wherein the scanning parameters comprise incident laser energy, scanning times, spot diameter, lap joint rate, low repetition frequency and high repetition frequency, and the incident laser energy is the minimum energy and E output by a laser_m5 numerical values are taken at equal intervals, the scanning frequency is 1-5 times, the diameter of a light spot is 100 micrometers, 500 micrometers, 1mm, 1.5mm or 2mm, the lap joint rate is 30%, 50%, 70% or 90%, the low repetition frequency is any one numerical value in the range of 1-10 Hz, and the high repetition frequency is any one numerical value in the range of a few KHz-a few tens KHz; each group of scanning parameters corresponds to a sample subjected to coating treatment;

then selecting a group of scanning parameters, selecting a sample subjected to coating treatment, placing the sample on a motor-driven translation table, and selecting 1cm from the center of the sample²The area adopts a nanosecond laser to carry out raster scanning according to the selected scanning parameters, so that the energy of the incident laser is always ensured to be less than the maximum laser energy E which can prevent the thin film element from being damaged_mThe online microscope is always aligned to the position of the pump laser irradiation detected sample to detect the states of the detected sample, the absorption material and the restraint layer in the laser irradiation process in real time; removing the restraint layer covered on the surface of the sample, removing residual absorbing materials on the surface by using acetone and ethanol solution, and further carrying out spraying and ultrasonic cleaning on the sample to finish laser-induced plasma impact post-treatment of an optical thin film element;

finishing the post-treatment process of the laser-induced plasma of the optical thin film element under all scanning parameter combinations according to the method;

(5) obtaining the functional damage threshold F of all thin film elements after the post-treatment of the laser-induced plasma with different scanning parameters according to the method in the step (2)_thi-ns；

(6) Replacing the nanosecond laser in the step (4) with a picosecond laser or a femtosecond laser, repeating the steps (4) to (5), and respectively obtaining the functional damage threshold F of the optical thin film element after the post-treatment of the laser-induced plasma of different scanning parameters by the picosecond laser and the femtosecond laser_thi-psAnd F_thi-fs；

(9) Comparing the functional damage threshold F of the optical film element which is not post-treated in step (2)_th0And (5) after nanosecond laser-induced plasma impact treatment, performing functional damage threshold F on the thin film element_thi-nsAnd (6) a functional damage threshold F of the thin film element after picosecond and femtosecond laser-induced plasma post-treatment_thi-psAnd F_thi-fsSelecting the maximum functional damage threshold value as the optimal functional damage threshold value of the optical thin film element, wherein the corresponding pulse width and scanning parameters are the optimal parameters;

and performing laser-induced plasma post-treatment on the optical thin film element by adopting the optimal parameters to improve the laser damage resistance of the optical thin film element.

The invention has the following beneficial effects:

1. the method for improving the laser damage resistance of the optical film element can simultaneously reduce the defect density of structural and absorption defects in the film, improve the mechanical properties such as the binding force between film interfaces and the like, and solve the problems that the existing post-treatment technology is only effective to a small part of film element types and has limited improvement effect.

2. The method for improving the laser damage resistance of the optical film element has no limitation on the type, the structure, the deposition parameters and the applicable laser wavelength of the optical film element, and optical films such as electron beam evaporation, magnetron sputtering and electron beam evaporation inclined deposition can be compatible.

3. The method for improving the laser damage resistance of the optical thin film element is not limited by the size of the optical element, is also suitable for large-caliber optical thin film elements, and provides more comprehensive experimental data and theoretical guidance for the function realization of a large-caliber precise optical system and the stability of the system in long-time operation.

4. On the basis of the action of laser-induced plasma, the invention considers the situation of laser irradiation with high and low repetition frequencies, namely, the heat treatment action without heat accumulation is realized, so that the heat treatment effect can be determined, and the laser damage resistance of the element can be improved to a greater extent.

5. The method can adjust the process parameters such as the incident laser energy, the lap joint rate and the like in real time according to the laser damage resistance requirement and the judgment standard of the optical thin film element until the engineering requirement is met, and has the advantages of simple and reliable realization and wide applicability.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

The invention provides a method for improving the laser damage resistance of an optical film element on the basis of laser-induced plasma, which comprises the following steps:

(1) plating a batch of optical thin film elements as samples, and carrying out spraying and ultrasonic cleaning;

(2) obtaining a threshold value of functional damage of the optical thin film element, wherein the threshold value of functional damage is defined according to the standard of functional damage of the element in the test standard of ME L01-013-0D small-caliber optical elements, namely, the threshold value does not appear to be 1cm²The area has more than 10 damage pits, the damage pits are more than 100 mu m, and the maximum energy of any condition of the damage pits in the growth under the subsequent laser action is the functional damage threshold of the sample.

The specific method comprises the following steps:

(2.1) randomly selecting an optical thin film element as a tested sample, fixing the tested sample on an electric translation table, controlling the two-dimensional movement of the tested sample by the electric translation table, and aligning the position of the pump laser irradiated tested sample by an online monitoring system for diagnosing the occurrence of damage and accurately positioning;

(2.2) scanning the surface of the sample to be measured by a raster scanning mode (namely that light spots are overlapped by 90 percent of laser peak energy)²Region of (a), setting a maximum energy flow step E_m(E_mSetting a reference engineering requirement, wherein the reference engineering requirement is usually set to be higher than the index of the engineering requirement by 3-5J/cm²) Setting an initial energy flow step E₀(typically taken at 1,2, or 3J/cm²) Δ E (Δ E ═ 1 to 10J/cm)²) Is raised while E₀And Δ E is taken to be such that (E)_m-E₀) The value of/. DELTA.E is [10,12 ]]The largest integer within the interval; scanning according to the sequence of energy flow steps from low to high, scanning the next step after scanning one energy flow step, pausing the scanning of the next step after scanning the complete test area of the energy flow step once the energy flow step is damaged in the scanning process, and entering the step (2.3) to judge the size of the damaged point if the number of pit-breaking points of the energy flow step is not more than 10; otherwise, stopping the test, wherein the laser energy density corresponding to the previous energy flow step is the functional damage threshold F of the tested sample_th0(i.e. the maximum laser energy density after laser irradiation, which causes the change of the optical element not enough to affect the overall performance of the system), the step (3) is carried out;

(2.3) moving the tested sample, sequentially positioning all damage pits appearing in the scanning process, firstly judging whether the sizes of all the damage pits exceed 100um, and if the sizes of the damage pits do not exceed 100um, entering the step (2.4) to carry out growth test on the damage pits;

if the size of one damaged point exceeds 100um, stopping the test, and the laser energy density corresponding to the previous energy flow step is the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

(2.4) irradiating the damage point with the size not exceeding 100um and N (N100, 200, 300.. 10000) pulses at the energy flow step for generating the damage, and if the damage pit does not grow after N pulses, continuing to irradiate the N pulses until the growth phenomenon occurs or the energy E is reached_mIf damage occurs during growth testStopping the test under the condition of wound growth, wherein the laser energy density corresponding to the maximum energy flow step without growth is the functional damage threshold F of the tested sample_th0And (4) turning to the step (3);

if the energy E is reached_mMoving the tested sample to the starting point of the test area without increasing all the damage points, turning to the step (2.2), and continuing the scan test of energy flow lifting until the energy flow lifting reaches 1cm²The area has more than 10 damaged pits or the damaged pits are larger than 100 mu m or any damaged pit grows under the action of subsequent laser, and the laser energy density corresponding to the previous energy flow step at the moment is the functional damage threshold F of the tested sample_th0；

(3) Carrying out coating treatment of the optical film element: the surfaces of other optical thin film elements in the same batch are covered with a layer of absorbing material to generate high-temperature high-pressure plasma. The absorbing material can adopt black paint or other flexible films which can ensure 100% to completely absorb the incident laser energy, the thickness of the absorbing material is 0.5 mm-1.0 mm, meanwhile, the thickness uniformity deviation of each part of the absorbing layer is ensured to be less than 10 mu m, the surface of the whole optical film element is covered, and in order to generate larger impact pressure and improve the acting time of plasma, the surface of the absorbing material can be covered with a restraint layer (in the embodiment, silicate glass with the thickness of 1.0 mm-2.0 mm is selected as the restraint layer); several samples were then obtained after the coating treatment.

(4) Carrying out laser-induced plasma shock post-treatment on the optical thin film element:

firstly, determining the value combination of scanning parameters: incident laser energy (minimum energy and E at laser output)_mAnd 5 values are taken at equal intervals, the scanning times (1 to 5 times), the spot diameter (value: 100 μm, 500 μm, 1mm, 1.5mm or 2mm), overlap ratio (value: 30%, 50%, 70% or 90%), a low repetition frequency (any value of 1Hz to 10 Hz) and a high repetition frequency (any value of several KHz to several tens of KHz); each set of scan parameters corresponds to a coated sample.

Then selecting a group of scanning parameters and selecting a position passing through the coatingPlacing the sample on an electric translation table, and selecting 1cm from the center of the sample²The area adopts a nanosecond laser to carry out raster scanning according to the selected scanning parameters, so that the energy of the incident laser is always ensured to be less than the maximum laser energy E which can prevent the thin film element from being damaged_mThe online microscope is always aligned to the position of the pump laser irradiation detected sample to detect the states of the detected sample, the absorption material and the restraint layer in the laser irradiation process in real time; and then removing the restraint layer covered on the surface of the sample, removing residual absorbing materials on the surface by using acetone and ethanol solution, and further carrying out spraying and ultrasonic cleaning on the sample to finish the laser-induced plasma impact post-treatment of the optical thin film element.

And finishing the post-treatment process of the laser-induced plasma of the optical thin film element under all scanning parameter combinations according to the method.

(5) Obtaining the functional damage threshold F of all thin film elements after the post-treatment of the laser-induced plasma with different scanning parameters according to the method in the step (2)_thi-ns。

(6) Replacing the nanosecond laser in the step (4) with a picosecond laser or a femtosecond laser, repeating the steps (4) to (5), and respectively obtaining the functional damage threshold F of the optical thin film element after the post-treatment of the laser-induced plasma of different scanning parameters by the picosecond laser and the femtosecond laser_thi-psAnd F_thi-fs；

(10) Comparing the functional damage threshold F of the optical film element which is not post-treated in step (2)_th0And (5) after nanosecond laser-induced plasma impact treatment, performing functional damage threshold F on the thin film element_thi-nsAnd (6) a functional damage threshold F of the thin film element after picosecond and femtosecond laser-induced plasma post-treatment_thi-psAnd F_thi-fsSelecting the maximum functional damage threshold value as the optimal functional damage threshold value of the optical thin film element, wherein the corresponding pulse width and scanning parameters are the optimal parameters;

(11) and performing laser-induced plasma post-treatment on the optical thin film element by adopting the optimal parameters to improve the laser damage resistance of the optical thin film element.

(12) The types of the optical thin film elements are changed, ⑴ -8 are repeated, and the effect of improving the laser damage resistance of the laser-induced plasma on the optical thin film elements of different types can be clarified.