阅读说明：本技术 一种光学薄膜激光损伤阈值测试系统及其方法 (Optical film laser damage threshold testing system and method ) 是由 赵元安 马浩 邵建达 李大伟 刘晓凤 邵宇宸 李成 李婷 于 2019-08-06 设计创作，主要内容包括：本发明涉及一种光学薄膜激光损伤阈值测试方法,包括如下步骤：S1、测试得到光学薄膜单脉冲激光损伤时的激光能量密度F<Sub>th</Sub>；S2、使单脉冲激光对光学薄膜进行辐照,记录下光学薄膜表面激光损伤边界不再增大时的激光损伤区域边界坐标(x<Sub>i</Sub>,y<Sub>i</Sub>),同时记录下单脉冲激光辐照的次数n；S3、将激光能量密度的高斯分布与激光损伤区域分布对照,得到光学薄膜多脉冲激光辐照损伤时的激光损伤阈值F<Sub>N</Sub>；S4、不断改变入射的激光能量密度,重复执行步骤S2、S3,得到不同脉冲数目的飞秒激光辐照下光学薄膜的激光损伤阈值曲线。有益效果是不仅仅保证多脉冲激光辐照下光学薄膜激光损伤阈值测量准确性、同时大大提高多脉冲辐照下光学薄膜损伤阈值的测试效率。(The invention relates to a method for testing laser damage threshold of an optical film, which comprises the following steps: s1, testing to obtain the laser energy density Fth of the optical film during single-pulse laser damage; s2, irradiating the optical film by the single pulse laser, recording the boundary coordinates (xi, yi) of the laser damage area when the laser damage boundary on the surface of the optical film is not increased any more, and recording the number n of times of irradiation of the single pulse laser; s3, comparing Gaussian distribution of laser energy density with distribution of laser damage areas to obtain a laser damage threshold FN when the optical film is damaged by multi-pulse laser irradiation; and S4, continuously changing the energy density of the incident laser, and repeatedly executing the steps S2 and S3 to obtain the laser damage threshold curve of the optical film under the irradiation of the femtosecond laser with different pulse numbers. The method has the advantages of ensuring the accuracy of measuring the laser damage threshold of the optical film under multi-pulse laser irradiation and greatly improving the efficiency of testing the damage threshold of the optical film under multi-pulse irradiation.)

1. The utility model provides an optical film laser damage threshold test system which characterized in that: the testing system comprises a femtosecond laser (1), two reflectors (2), an energy attenuation system (3), a mechanical shutter (4), a focusing lens (5), a wedge-shaped sheet (6), a beam quality analyzer (7), an energy meter (8), a two-dimensional moving platform (10) for placing an optical film (9), a CCD camera (11) and a computer (12), wherein the computer (12) is provided with a data output card (13) and a motion control card (14); the femtosecond laser device (1) is connected to a data output card (13), the two-dimensional moving platform (10) is connected to a motion control card (14), the light beam quality analyzer (7), the energy meter (8) and the CCD camera (11) are connected to a computer (12), the data control card (13) is used for controlling the femtosecond laser device (1) to output femtosecond laser, the motion control card (14) is used for controlling horizontal and vertical movement of the two-dimensional moving platform (10), the optical film (9) is installed on the two-dimensional moving platform (10), and the CCD camera (11) is aligned to the optical film (9); the femtosecond laser device (1), the two reflectors (2), the energy attenuation system (3), the mechanical shutter (4), the focusing lens (5) and the wedge-shaped sheet (6) are arranged on a laser light path, the beam quality analyzer (7) and the energy meter (8) are used for respectively collecting laser beams in the reflection direction of the wedge-shaped sheet (6), the beam quality analyzer (7) is used for laser quality analysis, and the energy meter (8) is used for measuring the energy of laser; the surface of the optical film (9) receives laser beams in the transmission direction of the wedge-shaped sheet (6), the reflecting mirror (2) and the energy attenuation system (3) are used for adjusting the laser energy density emitted by the femtosecond laser (1), the mechanical shutter (4) is used for adjusting the pulse number of the laser reaching the surface of the optical film (9), the focusing lens (5) is used for adjusting the focus of the laser beams to the surface of the optical film (9), and the CCD camera (11) is used for recording the position of laser spots on the surface of the optical film (9).

2. A method for testing laser damage threshold of optical film, wherein the method is operated on the testing system of claim 1, comprising the steps of:

s1, adjusting the incident laser to be single-pulse laser, moving the optical film (9) to a laser spot position, adjusting the peak laser energy density of the incident single-pulse laser from high to low, and testing by using a 1-on-1 mode to obtain the laser energy density Fth when the optical film (9) is damaged by the single-pulse laser;

s2, adjusting the laser energy density of the incident single-pulse laser to a certain value F0 lower than Fth, adjusting a mechanical shutter (4) to be in a normally open state, enabling the single-pulse laser to irradiate the optical film (9), recording the boundary coordinates (xi, yi) of a laser damage area when the laser damage boundary on the surface of the optical film (9) is not increased any more, and recording the number n of times of irradiation of the single-pulse laser;

S3, comparing the Gaussian distribution of the laser energy density with the distribution of the laser damage area, and calculating the laser damage threshold FN of the irradiation optical film (9) when the pulse number of the multi-pulse laser is N, wherein N is equal to the number N of times of single-pulse laser irradiation; the formula is as follows:

in the formula:

FN (xi, yi) -laser damage threshold, unit J/cm 2;

f0-incident single pulse laser peak laser energy density, unit J/cm 2;

(xi, yi) -laser damage area boundary coordinates, unit um;

ω x, ω y-gaussian radius of laser spot in transverse and longitudinal direction, unit um;

and S4, continuously changing the energy density of the incident laser, and repeatedly executing the steps S2 and S3 to obtain the laser damage threshold curve of the optical film (9) under the irradiation of the femtosecond laser with different pulse numbers.

3. the method for testing damage threshold of optical film according to claim 2, wherein: the laser wavelength emitted by the femtosecond laser (1) is 800 nm.

4. the method for testing damage threshold of optical film according to claim 2, wherein: the laser pulse width emitted by the femtosecond laser (1) is 65 fs-120 fs.

5. The method for testing damage threshold of optical film according to claim 2, wherein: the test method the repetition frequency of the femtosecond laser (1) is 1 kHz.

6. the method for testing damage threshold of optical film according to claim 2, wherein: the laser energy range output by the femtosecond laser (1) in the testing method is 0.1 mJ-1 mJ.

7. The method for testing damage threshold of optical film according to claim 2, wherein: the laser energy density range after the testing method is adjusted by the reflector (2) and the energy attenuation system (3) is 0.2J/cm 2-0.5J/cm 2.

8. The method for testing damage threshold of optical film according to claim 2, wherein: the optical film (9) used in the test method is a high-reflectivity dielectric film.

9. The method for testing damage threshold of optical film according to claim 2, wherein: the energy distribution of the laser facula in the testing method is Gaussian distribution.

[ technical field ] A method for producing a semiconductor device

the invention relates to the field of optical detection, in particular to a system and a method for testing an optical film damage threshold.

[ background of the invention ]

the damage of strong laser to the optical film restricts the development of laser to high power and high energy, and is also an important factor influencing the stability, reliability and service life of the optical film. With the continuous expansion of the application range of ultrashort laser, the importance of the damage resistance of the optical film or the optical element is increasingly prominent, and the accurate and efficient test of the damage threshold of the laser film is a prerequisite for improving the damage resistance of the laser film. In recent years, ISO11524-1 and ISO11524-2, which are international standards for damage to optical elements caused by laser light, have been issued by the International Committee for standardization.

At present, a method for measuring an optical thin film damage threshold under femtosecond laser multi-pulse irradiation mainly uses a standard probability method, namely, the pulse number of laser is fixed, incident laser energy is irradiated on the surfaces of different samples from high to low successively according to a certain energy step through an energy attenuation system until the maximum energy density of the samples without damage (zero probability damage) occurs, and at the moment, the energy density is considered as the laser damage threshold under the pulse number of the laser. The method has complicated operation steps, a plurality of energy steps are required to be tested under the irradiation of specific laser pulses, and each energy step is required to be tested for a plurality of points to find the maximum energy density of zero-probability damage, so that not only is time consumed in the measurement process, but also a large number of test samples are required.

Because the existing method for testing the damage of the optical film under the femtosecond laser multi-pulse irradiation is difficult to ensure the high efficiency and the accuracy of the test of the damage threshold of the optical film, the requirement for the simple, high-efficiency and accurate test of the damage threshold of the optical film under the femtosecond laser multi-pulse irradiation is more and more urgent.

[ summary of the invention ]

The invention aims to provide an optical film damage threshold value testing system which not only ensures the accuracy of optical film laser damage threshold value measurement under multi-pulse laser irradiation, but also greatly improves the testing efficiency of the optical film damage threshold value under multi-pulse irradiation.

in order to achieve the purpose, the technical scheme adopted by the invention is that the optical thin film laser damage threshold testing system comprises a femtosecond laser, two reflectors, an energy attenuation system, a mechanical shutter, a focusing lens, a wedge-shaped sheet, a beam quality analyzer, an energy meter, a two-dimensional moving platform for placing an optical thin film, a CCD camera and a computer, wherein the computer is provided with a data output card and a motion control card; the femtosecond laser is connected to a data output card, the two-dimensional mobile platform is connected to a motion control card, the beam quality analyzer, the energy meter and the CCD camera are connected to a computer, the data control card is used for controlling the femtosecond laser to output femtosecond laser, the motion control card is used for controlling the horizontal and vertical movement of the two-dimensional mobile platform, the optical film is installed on the two-dimensional mobile platform, and the CCD camera is aligned with the optical film; the femtosecond laser, the two reflectors, the energy attenuation system, the mechanical shutter, the focusing lens and the wedge-shaped sheet are arranged on a laser light path, the beam quality analyzer and the energy meter are used for respectively collecting laser beams in the reflection direction of the wedge-shaped sheet, the beam quality analyzer is used for laser quality analysis, and the energy meter is used for measuring the energy of the laser; the optical film surface receives laser beams in the transmission direction of the wedge-shaped sheet, the reflector and the energy attenuation system are used for adjusting the laser energy density emitted by a femtosecond laser, the mechanical shutter is used for adjusting the pulse number of the laser reaching the optical film surface, the focusing lens is used for adjusting the focal point of the laser beams to the optical film surface, and the CCD camera is used for recording the position of laser spots on the optical film surface.

the invention further aims to provide an optical film damage threshold value testing method which not only ensures the accuracy of optical film laser damage threshold value measurement under multi-pulse laser irradiation, but also greatly improves the efficiency of optical film damage threshold value testing under multi-pulse irradiation.

In order to achieve the above object, the technical solution adopted by the present invention is a method for testing a laser damage threshold of an optical thin film, wherein the method for testing the laser damage threshold of the optical thin film is operated on the test system, and comprises the following steps:

S1, adjusting the incident laser to be a single-pulse laser, moving the optical film to a laser spot position, adjusting the peak laser energy density of the incident single-pulse laser from high to low, and testing by using a 1-on-1 mode to obtain the laser energy density Fth when the optical film is damaged by the single-pulse laser;

S2, adjusting the laser energy density of the incident single-pulse laser to a certain value F0 lower than Fth, adjusting a mechanical shutter to be in a normally open state, irradiating the optical film by the single-pulse laser, recording the boundary coordinates (xi, yi) of the laser damage area when the laser damage boundary on the surface of the optical film is not increased any more, and simultaneously recording the irradiation times n of the single-pulse laser;

S3, comparing the Gaussian distribution of the laser energy density with the distribution of the laser damage area, and calculating the laser damage threshold FN of the irradiation optical film when the pulse number of the multi-pulse laser is N, wherein N is equal to the number N of times of single-pulse laser irradiation; the formula is as follows:

In the formula:

FN (xi, yi) -laser damage threshold, unit J/cm 2;

F0-incident single pulse laser peak laser energy density, unit J/cm 2;

(xi, yi) -laser damage area boundary coordinates, unit um;

ω x, ω y-gaussian radius of laser spot in transverse and longitudinal direction, unit um;

And S4, continuously changing the energy density of the incident laser, and repeatedly executing the steps S2 and S3 to obtain the laser damage threshold curve of the optical film under the irradiation of the femtosecond laser with different pulse numbers.

Preferably, the laser wavelength emitted by the femtosecond laser is 800 nm.

Preferably, the laser pulse width emitted by the femtosecond laser is 65 fs-120 fs in the test method.

preferably, the repetition frequency of the femtosecond laser is 1kHz in the above test method.

Preferably, the laser energy output by the femtosecond laser in the test method is 0.1 mJ-1 mJ.

preferably, the laser energy density range after the adjustment of the reflector and the energy attenuation system in the test method is 0.2J/cm 2-0.5J/cm 2.

preferably, the optical thin film used in the above test method is a highly reflective dielectric film.

Preferably, the energy distribution of the laser spot of the test method is gaussian.

compared with the prior art, the invention has the following beneficial technical effects:

1. the test system and the method for the laser damage threshold of the optical film under femtosecond laser multi-pulse irradiation can effectively determine the damage threshold of the optical film under femtosecond laser multi-pulse irradiation, provide a reasonable test means for determining the multi-pulse laser damage threshold of the optical film in an actual laser system, and provide a basis for the application life of the optical film in the femtosecond laser system.

2. according to the invention, the energy density at the boundary of the damaged area, namely the laser damage threshold of femtosecond laser multi-pulse irradiation, can be obtained by comparing the laser beam with Gaussian energy density distribution and taking the laser peak energy density as the incident energy density, and the damage threshold measurement under the multi-pulse irradiation of the optical film can be simply and efficiently realized.

3. the system and the method for testing the laser damage threshold of the optical thin film under femtosecond laser multi-pulse irradiation have high applicability, and can test the multi-pulse laser damage threshold of any optical thin film with different material systems, different film systems, different functions and the like; the number of test samples and the test time are saved, and the multi-pulse damage threshold of the optical film can be estimated by using a tiny area.

[ description of the drawings ]

FIG. 1 is a schematic structural diagram of a system for testing laser damage threshold of an optical thin film.

FIG. 2 is a schematic diagram of a computer structure of a laser damage threshold testing system for optical thin films.

FIG. 3 is a diagram of steps of a method for testing laser damage threshold of an optical film.

FIG. 4 is an SEM image of a damaged area of an optical film according to a laser damage threshold test method for the optical film.

FIG. 5 is a graph of the damage threshold of an optical film according to a method for testing the laser damage threshold of an optical film.

the reference numerals and components referred to in the drawings are as follows: the system comprises a laser 1, a laser 2, a reflector 3, an energy attenuation system 4, a mechanical shutter 5, a focusing lens 6, a wedge-shaped sheet 7, a beam quality analyzer 8, an energy meter 9, an optical film 10, a two-dimensional moving platform 11, a CCD camera 12, a computer 13, a data output card 14 and a motion control card.

[ detailed description ] embodiments

The invention is further described with reference to the following examples and with reference to the accompanying drawings.