CN102179622A - Method for preparing microstructural target by using laser to improve laser propulsion impulse coupling coefficient - Google Patents

Abstract

A method for improving laser propulsion impulse coupling coefficient by using laser to prepare microstructure target. The present invention proposes a method for preprocessing solid targets in ablation laser propulsion technology by using focused near-infrared femtosecond laser pulses to produce various microstructures on the surface to effectively enhance its impulse coupling coefficient. The microstructured solid targets prepared by femtosecond laser pulses include various types of protrusion structures and groove structures that are beneficial to enhance light absorption. Using the high-sensitivity torsion balance precision measurement device established in the experiment, it is known that within the range of laser flux variation of 0.6-100 J/cm2, the impulse coupling coefficient of these microstructured solid targets is higher than that of ordinary planar targets without femtosecond laser pretreatment. About 170%. The new method for effectively enhancing the conversion of light energy to mechanical energy in the process of laser ablation proposed by the invention has potential important applications in the field of laser propulsion technology.

Description

Method of Improving Coupling Coefficient of Laser Propelling Impulse by Using Laser to Prepare Microstructure Target

technical field

The invention belongs to the field of structural design and production of solid targets used in laser propulsion technology, and in particular relates to the preparation of various forms of microstructures on the surface of solid targets by applying femtosecond laser pulses, and the solid targets of these microstructures are shown by precise experimental measurements The impulse coupling performance in ablation laser propulsion can be effectively improved and enhanced.

Background technique

Laser propulsion technology is the first new type of propulsion technology that may realize low-earth orbit launch missions since human beings sent artificial satellites into earth orbit in the 1950s. Compared with traditional chemical propulsion technology, laser propulsion technology has the advantages of higher load ratio, larger adjustment range of propulsion parameters (impulse coupling coefficient and specific impulse), and can exceed the maximum speed limit of each stage of chemical fuel rocket. In the near future, laser propulsion technology is expected to play an important role in space junk removal, aircraft attitude adjustment, aircraft orbital maneuvering, low-Earth orbit launches and even deep space missions.

The original concept of laser propulsion was proposed in 1969 by R. L. Geisler et al. of the U.S. Air Force Rocket Propulsion Laboratory (AFRPL). In 1974, A. N. Pirri and others carried out a long-pulse laser propulsion experiment with a pulse width of 100s and a wavelength of 10.6m, and obtained an impulse coupling coefficient of 10-100 dyne/W [Propulsion by absorption of laser radiation. AIAA J., 1974, 12(9): 1254-1261]. In 1997, L. N. Myrabo et al. used a 10 kW pulsed carbon dioxide laser with a single pulse energy of 400 J and a pulse repetition frequency of 25 Hz, and used air as a propellant to successfully test the wire-guided laser propulsion experiment for the first time. At the same time, C. R. Phipps et al. were also committed to the research on the impulse coupling coefficient and specific impulse generated by the interaction between pulsed laser and matter, and obtained the maximum impulse coupling produced by lasers with different wavelengths and different pulse widths through ablation. [Laser impulse coupling at 130 fs. Appl. Surf. Sci., 2006, 252(13): 4838-4844].

Since 2000, A. V. Pakhomov and others have used picosecond laser pulses to carry out research on ablation laser propulsion, and have studied various materials such as lead, aluminum, polyoxymethylene resin, and polytetrafluoroethylene under different laser fluxes and incident angles. The performance in ablative laser propulsion, looking for the most suitable combination of impulse coupling coefficient and specific impulse [Ablative laser propulsion: an update, part 1. ^2nd international symposium on beamed energy propulsion, 2004. 702: 166-177]. In 2002, V. V. Apollonov and others proposed to use a high repetition rate pulsed laser-induced shock wave sequence to form a strong shock wave close to the plane, thereby effectively improving the impulse coupling coefficient [Stable generation and merging of shock waves for lightcraft applications: part 1. 3 ^rd international symposium on beamed energy propulsion, 2005. 766: 205-215].

In 2002, T. Yabe and others covered the surface of the metal target with water to make a so-called water cannon target. Under the action of the pulsed laser with a pulse width of 5 ns output by the YAG laser, the impulse coupling coefficient of the water cannon target can be It reaches 350 dyne/W【Microairplane propelled by laser driven exotic target. Appl. Phys. Lett., 2002, 80(23): 4318-4320】, compared with the use of pure metal targets, the impulse coupling coefficient is doubled. Then they made further improvements on the basis of the water cannon target, and proposed two target structures, metal free water cannon target (MFWC) and water film cannon target (WFC), the impulse coupling coefficients reached 240 dyne/W and 368 respectively. dyne/W【Laser Propulsion Using Metal-Free Water Cannon Target. 3 ^rd international symposium on beamed energy propulsion, 2005. 766: 394-405】.

In China, in 2006, the research group of the Institute of Physics of the Chinese Academy of Sciences used a laser pulse with a center wavelength of 532 nm, a maximum single pulse energy of 800 mJ, and a pulse width of 7 ns to ablate a water-confined target (similar to a water cannon target) to obtain more than 250 dyne The impulse coupling coefficient of /W [Enhancement of coupling coefficient of laser plasma propulsion by water confinement. Appl. Phys. A, 2006, 85, 441-443]. In 2007, Tang Zhiping’s research group at the University of Science and Technology of China used water as a propellant, using YAG laser pulses with a wavelength of 1.064 μm, a single pulse energy of 1.2 J, and a pulse width of 12 ns, and obtained an impulse coupling coefficient of 350 dyne/W [laser water Experimental Research on Propulsion Technology, Experimental Mechanics, 2007, 22(1): 43-48]. Although the impulse coupling coefficient of laser propulsion, especially long-pulse laser propulsion, is much higher than that achieved by traditional chemical propulsion, the reflection of laser energy will inevitably occur during the interaction between the laser and the target. , scattering and transmission, resulting in a waste of laser energy. Therefore, how to develop a new type of target that absorbs laser energy efficiently has become an important topic in the field of laser propulsion at this stage.

In recent years, with the rapid development of ultrashort pulse laser technology, ultrafast laser processing technology has received more and more attention as an emerging means to realize the micro-nano-scale of functional structures and devices. Compared with the traditional planar technology, femtosecond laser micromachining and preparation technology has the advantages of simple operation, flexibility, high speed and low cost. At present, femtosecond lasers have been used to achieve submicron-scale processing on the surface or interior of various materials [Enhancing near-infrared avalanche photodiode performance by femtosecond laser microstructuring, Applied Optics, 2006, 45(35): 8825-8831] , to solve some key technical problems in practical applications.最近，研究者们将单束【Periodic ordering of random surface nanostructures induced by femtosecond laser pulses on metals, Journal of Applied Physics, 2007, 101: 034903；Ultra-broadband enhanced absorption of metal surfaces structured by femtosecond laser pulses", Optics Express, 16(15): 11259-11265 (2008)] or multi-beam 【Enhanced optical absorption of metals using interferometric femtosecond ablation, Optics Express, 2007, 15(21): 13838-13843】femtosecond laser irradiation to the metal surface induces Three different types of micro- and nanostructures have been produced, and it has been experimentally determined that these metal materials with micro-nano structures on the surface can have obvious anti-reflection properties for incident electromagnetic waves in a wide range of ultraviolet-visible-mid-infrared.However, Most of the existing related research is limited to the general description of femtosecond laser-induced micro-nano structure phenomenon. At present, we have not seen the application of femtosecond laser to the processing design and production of solid targets in ablation laser propulsion, and further measurement Related reports confirming its impulse coupling performance in ablative laser propulsion.

Contents of the invention

The technical problem to be solved by the present invention is: how to use femtosecond laser micromachining technology to carry out surface pretreatment on the solid target material in ablation laser propulsion, master the key technologies and methods, and effectively enhance Advance the impulse coupling coefficient generated by laser ablation, so as to further improve the overall efficiency of ablation laser propulsion. Compared with ordinary planar solid targets without femtosecond laser pretreatment, these solid targets with microstructures on the surface can increase the impulse coupling coefficient by about 170% during ablative laser propulsion. The technology of the invention is convenient, fast and highly operable, and overcomes the complicated procedures brought about by traditional structural design and manufacturing techniques.

The technical solution adopted by the present invention to solve this technical problem is: apply femtosecond laser pulses to prepare various forms of microstructures on the surface of ablation laser-propelled solid targets (taking metal samples as an example), and through the high-sensitivity torsion balance device Establish and accurately measure, discover and confirm that the impulse coupling coefficient of these microstructured solid targets is about 170% higher than that of corresponding targets without femtosecond laser pretreatment, providing a new method for further effectively improving laser propulsion efficiency. The steps are:

In the first step, the solid material selected for the ablation laser propulsion target, such as a metal aluminum sample, is mechanically ground and polished, then ultrasonically cleaned with deionized water, and then placed in a clean open container until it is air-dried, as target sample.

In the second step, in the air environment, use a microscope objective lens or an optical lens to focus the femtosecond laser pulse and then vertically irradiate the surface of the sample material after the first step of polishing, and observe the size of the ablation area on the surface of the material to find and Determine the exact position of the laser focus, and then adjust the sample surface to an appropriate position away from the focal plane along the reverse beam direction.

The third step is to set the femtosecond laser processing parameters as: pulse repetition frequency 1 kHz, pulse duration 50 femtoseconds, pulse center wavelength 800 nanometers, and make the incident laser pulse linearly polarized.

The fourth step is to place the solid target sample to be processed on the three-dimensional precision mobile platform, and control the movement of the sample in space through the computer. The minimum movement accuracy is 1 micron, and the sample movement speed can be in the range of 0.05-1 mm/s in the selection.

In the fifth step, under the condition of keeping the incident laser beam unchanged, by selecting the appropriate laser energy, and moving and scanning the solid target sample to be processed in a plane perpendicular to the beam, a large area on the surface of the solid target sample is realized. Area microstructure preparation. The moving direction of the sample can form any angle with the polarization direction, and the distance between two adjacent scanning lines can be selected within the range of 2-100 microns. When the average power of the incident femtosecond laser pulse is adjusted in the range of 40-250 milliwatts, it is observed that the microstructure morphology of the sample surface will change accordingly, and finally two different types of microstructure targets are obtained.

In the sixth step, the solid target sample after the femtosecond laser treatment in the fifth step is ultrasonically cleaned with deionized water to effectively remove the deposits attached to the surface of the sample, and the surface is subjected to microscopic observation and measurement. The seventh step is to apply the surface microstructure solid target successfully prepared in the sixth step to the experimental system of ablation laser propulsion, and to accurately measure its impulse coupling coefficient during the laser ablation process by establishing a high-sensitivity torsion balance device ;

The eighth step, in the process of advancing the ablation laser, when the incident laser energy is given, the laser flux in the spot irradiation area can be changed by adjusting the distance between the solid target and the focusing lens, so that the ordinary planar target can be measured respectively And the relationship between the ablation laser propulsion impulse coupling coefficient of the microstructure target and the laser flux, and then through the analysis of the measurement data, it can be found that the microstructure solid target can effectively improve the ablation laser propulsion impulse coupling coefficient.

The femtosecond laser pulse focusing described in the second step above uses a microscope objective lens or an optical lens, and the surface of the solid target sample is adjusted to a position range of 10-250 microns away from the focal plane along the direction of the reverse beam, so as to avoid High laser fluence can cause deep ablation of target sample surface.

The moving speed of the solid target sample mentioned in the fourth step above is selected in the range of 0.05-1 mm/s, the minimum moving accuracy is 1 micron, and the distance between two adjacent moving scanning lines is selected in the range of 2-100 microns .

The moving scanning direction of the solid target sample described in the fifth step above forms an arbitrary angle with the polarization direction of the incident femtosecond laser pulse; the average power of the incident laser pulse varies within the range of 40-250 milliwatts; prepared on the surface of the target sample to obtain The types of microstructures include: periodically arranged granular protrusion structures and periodically arranged groove structures.

The beneficial effects of the present invention are:

(1) Due to the extremely short duration of the femtosecond laser pulse, even a small laser pulse energy can have a very high peak power. The peak power of a single laser pulse in the present invention can be as high as 4×10 ¹⁰ watts, which will cause many nonlinear physical effects in the process of femtosecond laser action on the one hand, so that the metal surface can self-organize to form micro-nanometers of different shapes. On the other hand, the ultra-fast pulse duration will fundamentally weaken and eliminate the heat conduction effect of the material during the laser action, so that the spatial range of laser processing can be controlled at the submicron or nanometer level. Compared with the traditional planar exposure technology, the femtosecond laser preparation process of the present invention has the advantages of being more convenient, faster, without other auxiliary environments and processes, and the surface of the sample can self-organize to form microstructures of various forms.

(2) Currently there are literature [Compact and robust laser impulse measurement device, with ultrashort pulse laser ablation results[C]. Beamed energy propulsion: 5 ^th international symposium on beamed energy propulsion, AIP conference proceedings, New York: Americanys Institute of Physicians , 2008, 997: 147-158; Light propulsion of microbeads with femtosecond laser pulses[J]. Opt. Express, 2004, 12(15): 3590-3598] The impulse coupling coefficient of the laser is generally several dynes/watt (1 dyne = 10 ^-5 Newton), and the laser propulsion efficiency is low. The metal target thruster with surface microstructure described in the present invention can increase the impulse coupling coefficient by about 170%, and is expected to have important application prospects in applications related to laser propulsion.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a scanning electron micrograph of an ordinary planar metal aluminum target sample not treated by the method of the present invention in Example 1.

Fig. 2 is a scanning electron micrograph of a microstructured aluminum target sample obtained after pretreatment with a femtosecond laser with an average power of 40 milliwatts using the method of the present invention in Example 2.

Fig. 3 is a scanning electron micrograph of a microstructure metal aluminum target sample obtained after pretreatment with a femtosecond laser with an average power of 140 mW used in Embodiment 3 of the present invention.

Fig. 4 is a scanning electron micrograph of a microstructured aluminum target sample obtained after pretreatment with a femtosecond laser with an average power of 250 mW used in Embodiment 4 of the present invention.

Fig. 5 is a diagram of a device for measuring the impulse coupling coefficient of a solid target during ablation laser propulsion used in implementing 1, 2, 3, and 4 of the present invention. Among them: 1 means ultrashort laser pulse; 2 means optical lens with focal length f=100 mm; 3 means solid target sample; 4 means helium-neon laser beam; 5 means optical lens with focal length f=705 mm; 6 means CCD detector; 7 represents an optical fiber; 8 represents a liftable periscope device.

表示未经飞秒激光预处理的普通平面靶所得结果；

表示经过平均功率250毫瓦飞秒激光制备获得的微结构靶的所得结果；

表示经过平均功率140毫瓦飞秒激光制备获得的微结构靶的所得结果；

表示经过平均功率40毫瓦飞秒激光制备获得的微结构靶的所得结果。Fig. 6 is the relationship diagram of the impulse coupling coefficient changing with the incident laser flux in different metal target samples measured in implementation 1, 2, 3, and 4 of the present invention during the ablation laser propulsion process, wherein

Indicates the results obtained by ordinary planar targets without femtosecond laser pretreatment;

Represents the obtained results of the microstructure target prepared by the femtosecond laser with an average power of 250 milliwatts;

Represents the obtained results of the microstructure target prepared by the femtosecond laser with an average power of 140 milliwatts;

Shows the results obtained for microstructured targets prepared by a femtosecond laser with an average power of 40 mW.

Detailed ways

Example 1

In the first step, the 10×10×2 cubic millimeter block aluminum target sample was ground and mechanically polished with 400-800 water sandpaper step by step, and the scanning electron micrograph of the sample surface was shown in Figure 1. Ultrasonic cleaning with deionized water, then place it in a clean open container for use;

In the second step, a high-sensitivity torsion balance device was established to accurately measure the momentum generated by the above-mentioned ordinary metal aluminum target sample during the ablation laser propulsion process, and to study the enhancement degree of the impulse coupling. The experimental setup is shown in Fig. 5(a). In order to prevent the influence of air flow on the measurement of the torsion balance, the entire torsion balance device is placed in an airtight plexiglass cover. The ultra-short laser pulses used to ablate the target and the He-Ne laser signals used to detect the rotation of the torsion balance enter the inside of the cover through the optical window on the plexiglass cover. The torsion balance is composed of two parts: suspension wire and torsion pendulum. The suspension used for the torsion balance is a standard single-mode communication fiber (SMF-28e, Corning Inc.) with a cladding diameter of 125 μm and a core diameter of 8.2 μm. The hanging wire is 778mm long. The torsion pendulum of the torsion balance also consists of two parts. In the middle of the pendulum is a small square mirror coated with aluminum film, and the base is optical grade hardened acrylic; the rest of the pendulum is made of ordinary plexiglass material. During the experiment, two targets of the same material with the same mass were fixed on the L-shaped brackets at both ends of the pendulum.

In the third step, a helium-neon laser is used as the probe light source in the experiment. The helium-neon laser reflected by the twisting mirror is focused by a lens with a focal length of 705 mm (wavelength of 632.8 nm). In the experiment, the position of the receiving CCD was adjusted so that it was just on the focal plane of the He-Ne laser. When the focused laser pulse bombards the solid target sample on the pendulum to make the pendulum rotate, the propagating direction of the He-Ne laser signal changes after being reflected by the pendulum mirror, and its movement in space is detected and accepted by the high-sensitivity CCD. As shown in Figure 5(b), the laser pulse is focused by a lens with a focal length of 100 mm after being lifted by a liftable periscope. The focused laser pulse is used to ablate the target fixed on the torsion pendulum. The function of the liftable periscope in the experiment is to change the position of the laser pulse bombarding the target by lifting up and down, so that each measurement, each laser pulse bombards a new area on the target that has not been bombarded. In the experiment, the CCD was used to observe the backscattered light of the small energy femtosecond laser through the target sample to determine the position of the target relative to the focusing lens.

In the fourth step, the single laser pulse energy we used in the laser propulsion experiment is 0.65 millijoules, and the pulse width is 50 femtoseconds. By adjusting the distance between the solid target and the focusing lens, the incident laser flux can be achieved at 0.6 joules/square cm to ~100 J/cm2. When the incident laser flux is determined, the maximum rotation angle of the torsion balance can be obtained by measuring the moving distance of the light spot during the laser ablation process recorded by the CCD, so as to calculate the momentum generated by a single laser pulse ablation, and divide the momentum by the ablation The single pulse energy used gives the impulse coupling coefficient. The relationship between the impulse coupling coefficient of the ordinary planar metal aluminum target sample and the laser flux is measured in the experiment, as shown in Figure 6 shown in the curve. We can see that: when the incident laser flux increases gradually, the impulse coupling coefficient of the solid target sample increases first and then decreases. When the incident laser flux is about 9 J/cm The impulse coupling coefficient reaches a maximum value of about 4.5 dyne/watt.

Example 2

The first step is the same as in Example 1.

In the second step, in the air environment, the incident femtosecond laser pulse is vertically focused on the solid metal aluminum target sample processed in the first step using a microscope objective lens or an optical lens, and the sample surface is adjusted to In the range of 10-250 microns away from the focal plane;

The third step is to set the experimental parameters for femtosecond laser preparation: pulse repetition frequency 1 kHz, pulse width 50 femtoseconds, pulse center wavelength 800 nanometers, and the distance between adjacent laser processing scribe lines can be 20-100 microns The scanning speed of sample movement can be selected within the range of 0.05-1 mm/s, and the polarization direction of femtosecond laser and the scanning direction of sample movement can be at any angle.

The fourth step is to adjust the average power of the incident laser pulse to 40 milliwatts. After the metal aluminum target sample is processed by the above-mentioned laser irradiation method, a peculiar microstructure can be observed on its surface through a scanning electron microscope, as shown in Figure 2 Show. It is composed of many micron-scale protrusions and grooves. These microstructures make the surface of the metal target sample rough, similar to a porous absorber. Directly viewed with the naked eye, the surface color of the metal target sample covered with microstructures becomes dark.

In the fifth step, other technical and experimental conditions are the same as step two in Example 1, except that the metal aluminum target sample with the above-mentioned surface microstructure is used.

The sixth step is the same as step three in embodiment 1.

The seventh step is the same as step four in embodiment 1. The relationship between the impulse coupling coefficient of the microstructure metal aluminum target sample and the laser flow rate is measured in the experiment, as shown in Figure 6 shown in the curve. Compared with ordinary planar metal aluminum target samples, the impulse coupling coefficient of this type of surface microstructure metal aluminum target samples has been improved, and the maximum value has increased to 6.5 dyne/watt, but the corresponding laser flux has been reduced to 2.1 Joules/square centimeter. We think this may be caused by the lower laser ablation threshold due to the surface microstructure of the aluminum target sample.

Example 3

曲线所示。我们发现在此条件下，微结构金属铝靶样品比普通平面金属铝靶仍然具有较高的冲量耦合系数，并与实施例2中获得的结果大致相同。Except that the average power of the incident laser pulse was adjusted to 140 milliwatts during the preparation of the microstructured solid target by the femtosecond laser, other technical steps and experimental conditions were the same as in Example 2. In this case, it was observed experimentally that the surface of the metal aluminum target sample irradiated by the femtosecond laser also formed a striped microstructure formed by a plurality of protrusions, and its scanning electron micrograph is shown in Figure 3 . Compared with Figure 2, we can see that when the incident laser power becomes larger, the size of the raised structure formed on the surface of the metal aluminum target sample gradually becomes smaller. The relationship between the impulse coupling coefficient of the surface microstructure metal aluminum target sample and the laser flow rate is shown in Figure 6.

shown in the curve. We found that under this condition, the microstructure metal aluminum target sample still has a higher impulse coupling coefficient than the common planar metal aluminum target, and the result is roughly the same as that obtained in Example 2.

Example 4

曲线所示。与实施例2、3中的情况相比较，此种条件下微结构金属铝靶样品的冲量耦合系数发生了进一步的提高。最大值增至7.7达因/瓦，与未经飞秒激光预处理的普通平面铝靶样品相比较，最大冲量耦合系数提高了约170%。Except that the average power of the incident laser pulse was adjusted to 250 milliwatts during the preparation of the microstructured aluminum target sample by the femtosecond laser, other technical steps and experimental conditions were the same as in Example 2. In this case, it was observed that the surface of the metal aluminum target sample irradiated by the femtosecond laser has no raised structure, and only periodically distributed groove structures are formed. The width of the groove is about tens of microns. The scanning electron micrograph is shown in Fig. 4. The relationship between the impulse coupling coefficient of this microstructure metal aluminum target sample and the laser flow rate is measured in the experiment, as shown in Figure 6

shown in the curve. Compared with the situation in Examples 2 and 3, the impulse coupling coefficient of the microstructure metal aluminum target sample is further improved under this condition. The maximum value increased to 7.7 dyne/watt, and compared with the common planar aluminum target sample without femtosecond laser pretreatment, the maximum impulse coupling coefficient increased by about 170%.

Claims (6)

1. A method for improving the laser propulsion impulse coupling coefficient by preparing a microstructure target with a laser, the steps of which are: In the first step, the solid material selected for the ablation laser propulsion target is mechanically ground and polished, then ultrasonically cleaned with deionized water, and then placed in a clean open container to be air-dried as the target sample; In the second step, in the air environment, the focused femtosecond laser pulse is irradiated vertically on the surface of the target sample material after the first step of polishing, and the laser is found and determined by observing the size of the ablation area on the surface of the target sample material. The exact position of the focal point, and then adjust the surface of the target sample material to a position away from the focal plane along the direction of the reverse beam; The third step is to set the parameters of the femtosecond laser pulse as: pulse repetition frequency 1 kHz, pulse duration 50 femtoseconds, pulse center wavelength 800 nanometers, and make the incident laser pulse linearly polarized; The fourth step is to place the solid target sample to be processed on the three-dimensional precision mobile platform, and use the computer to control the movement of the target sample in space; The fifth step is to realize the large-area microstructure on the surface of the solid target sample by selecting the laser energy and moving and scanning the target sample to be processed in a plane perpendicular to the beam while keeping the incident laser beam unchanged. preparation; In the sixth step, the solid target sample processed by the femtosecond laser pulse in the fifth step is ultrasonically cleaned with deionized water to effectively remove the deposits attached to the surface of the sample, and the surface is subjected to microscopic observation and measurement; In the seventh step, the solid target sample with microstructure on the surface successfully prepared in the sixth step is applied to the experimental system of ablation laser propulsion, and the high-sensitivity torsion balance device is established to accurately measure its performance during the laser ablation process. The impulse coupling coefficient of ; In the eighth step, when the energy of the ablation laser is given, the light flux in the irradiation spot area can be adjusted by changing the distance between the solid target sample and the focusing lens, so as to measure the ablation rate of the ordinary planar target and the microstructure target respectively. The relationship between impulse coupling coefficient and laser flux in laser propulsion. 2. The method according to claim 1, characterized in that: the femtosecond laser pulse focusing described in the second step adopts a microscope objective lens or an optical lens, and the surface of the solid target sample is adjusted to be 10° away from the focal plane along the direction of the reverse beam. -250 micron position range, which can avoid the deep ablation removal of the target sample surface caused by the high laser flux at the laser focus. 3. The method according to claim 1, characterized in that: the moving speed of the solid target sample in the fourth step is selected within the range of 0.05-1 mm/s, the minimum moving accuracy is 1 micron, and two adjacent The distance between moving scan lines is selected in the range of 2-100 microns. 4. The method according to claim 1, characterized in that: the moving scanning direction of the solid target sample in the above-mentioned 5th step is at any angle with the polarization direction of the incident femtosecond laser pulse; the average power of the incident laser pulse is between Changes in the range of 40-250 milliwatts; the types of microstructures prepared on the surface of the target sample include: periodically arranged granular protrusion structures and periodically arranged groove structures. 5. The method according to claim 1, characterized in that: the process of measuring the impulse coupling coefficient in the seventh step is: when the focused laser pulse bombards the solid target sample placed on the torsion pendulum and makes the torsion pendulum rotate, the detection beam passes through The movement change in the propagation direction behind the torsion mirror is detected by a high-sensitivity CCD; after the laser pulse is lifted by the periscope, it is focused by a lens with a focal length of 100 mm to the surface of the target sample fixed on the torsion. The laser pulse hits a specific location on the solid target such that each measurement, each laser pulse hits a new area of the target that was not bombarded. 6. The method according to claim 1, characterized in that: when the incident laser flux is determined in the above-mentioned eighth step, the spatial movement of the detection light spot during the ablation laser advancing process is measured by using a high-sensitivity CCD recorder The distance is to obtain the maximum rotation angle of the torsion balance, so as to calculate the momentum generated by a single laser pulse during the ablation process, and divide the momentum by the single pulse energy used in ablation to obtain the impulse coupling coefficient.

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