Method for preparing energetic material crystal microdefects based on femtosecond laser micromachining

Abstract

The invention discloses a method for preparing energetic material crystal microdefects based on femtosecond laser micromachining, and solves the problems that in the prior art, the regulation and control capability on energetic material microdefect structures is limited, and precise machining of complex micro-nano structures is difficult to achieve. The method comprises the following steps: establishing a femtosecond laser micromachining light path system; selecting energetic material crystals; presetting output parameters and processing parameters of the femtosecond laser; placing the sample under a high-precision microscope focusing system; starting a femtosecond laser, focusing the output femtosecond laser on the surface of the sample through a microscope objective lens after the output femtosecond laser is guided and modulated by a light beam, and controlling a focused light spot to carry out high-speed precise scanning on the surface of the sample by combining a high-speed precise three-dimensional scanning system; performing scanning processing on the target area to form an ablation area and generate a micro-area ablation product; meanwhile, an auxiliary air blowing system is started, dust generated in the machining area is blown away in real time through directional clean airflow, and it is ensured that laser energy directly and stably acts on the intrinsic surface, not shielded by the previous machining dust, of the material; and finally, carrying out post-treatment and characterization on the processed sample. According to the method, by means of the accurate positioning and scanning capability of a microscope system, accurate regulation and control of the micro-defect structure on the surface of the energetic material can be achieved, and a new way is provided for performance research of the energetic material.

Description

Technical Field

[0001] This invention relates to laser fabrication and performance control technology for micro / nano structures on the surface of energetic material crystals, specifically to a method for constructing controllable micro-defects in energetic material crystals based on femtosecond laser micromachining. Background Technology

[0002] Laser-initiated detonation technology using energetic materials boasts significant advantages such as high initiation precision, strong controllability, and good safety, making it a promising field for applications in aerospace, defense equipment, and special engineering. However, this technology currently faces challenges such as a high initiation energy threshold and limitations in laser size and cost, hindering its further practical application and miniaturization. According to the hotspot initiation theory, the detonation of energetic materials originates from "hot spots" formed in localized areas within the material under the influence of external energy. The number, size, and distribution of these hot spots directly affect the initiation sensitivity. Therefore, intentionally introducing microscopic defect structures into energetic materials to artificially increase and control hotspot formation is one effective way to reduce the laser initiation threshold and improve initiation sensitivity.

[0003] Currently, methods to improve the laser initiation sensitivity of energetic materials mainly include doping with light-absorbing nanoparticles or light-scattering microparticles. For example, ED Aluker et al. added micron-sized MgO particles to PETN, utilizing the multiple scattering effect of impurities on the laser to increase the laser propagation path in the material, thereby improving laser absorption efficiency and reducing the initiation energy threshold (EDAluker, AG Krechetov, AY Mitrofanov, et al. Laser initiation of energetic materials: selective photoinitiation regime in PentaerythritolTetranitrate[J]. Journal of Physical Chemistry C, 2011, 115(4): 6893-6901). Although such methods can enhance photothermal conversion efficiency, the introduced impurities may alter the original chemical composition and stability of the material, posing challenges in terms of process controllability and consistency.

[0004] Another approach is to directly fabricate micro- and nano-defect structures in energetic material crystals using micromachining techniques, thereby controlling their photoresponse characteristics while maintaining material purity. Femtosecond lasers, with their ultrashort pulses, extremely high peak power, and nonlinear absorption characteristics, can achieve submicron-scale "cold processing" with almost no thermal impact, making them particularly suitable for the fine modification of heat-sensitive and fragile materials like energetic materials. For example, SD McGrane et al. used femtosecond lasers to fabricate microstructure defects in PETN and HMX crystals, verifying the technical feasibility of this method (SD McGrane, A. Grieco, KJRamos, et al. Femtosecond micromachining of internal voids in high explosive crystals for studies of hot spot initiation[J]. Journal of Applied Physics,2009, 105(7): 073505). However, the study also points out that femtosecond lasers still have the following key problems in the preparation of micro-defects in energetic materials: First, the energy control precision of femtosecond lasers is insufficient. As a special type of explosive material, the preparation of micro-defects in energetic materials places very high demands on the micro-machining parameters of femtosecond lasers. If the energy is too low, the required defect array cannot be prepared; if the energy is too high, micro-explosion will cause extended cracks, which will seriously affect the forming accuracy of the defects. Second, the correspondence between process parameters and defect structures is not yet clear. It is impossible to reliably obtain the defect structure with the preset morphology by adjusting the laser parameters, thus limiting its practical application in controlling the laser initiation sensitivity of energetic materials. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of the current method of processing micro-defects in energetic materials using femtosecond lasers, such as the single defect morphology, poor process controllability, easy induction of crystal propagation crack damage, and difficulty in effectively controlling the laser initiation sensitivity of the material through the defect structure. The invention provides a femtosecond laser micromachining method that can accurately control the micro-defect morphology, avoid crystal damage, and effectively control the laser initiation sensitivity of energetic materials.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for fabricating micro-defects in energetic material crystals based on femtosecond laser micromachining, through precise control of the processing parameters of the femtosecond laser and the synergistic effect of the auxiliary gas flow, can fabricate periodic micro / nano structures with controllable morphology, size, and density on the surface of energetic materials without introducing crystal damage; the method includes the following steps:

[0008] Step 1: Construct a femtosecond laser micromachining device; the femtosecond laser micromachining device includes a femtosecond laser, a mirror system, a microscope focusing system, an auxiliary air blowing system, and a high-speed precision three-dimensional scanning system arranged sequentially along the laser optical path;

[0009] Step 2: Select energetic material crystal samples;

[0010] Step 3: Preset the processing parameters of the femtosecond laser, including laser wavelength, pulse width, laser power and repetition frequency; preset the scanning parameters of the high-speed precision 3D scanning system, including scanning path, scanning mode, scanning interval, scanning speed and number of repeated scans;

[0011] Step 4: Place the energetic material crystal sample processed in Step 2 below the microscope focusing system and at the focal length of the microscope objective; turn on the femtosecond laser and output a femtosecond laser corresponding to the processing parameters in Step 3. The femtosecond laser passes through the mirror system and is focused onto the surface of the energetic material crystal sample by the microscope focusing system to form a focused spot.

[0012] Step 5: Turn on the high-speed precision 3D scanning system and scan the surface of the energetic material crystal sample according to the scanning parameters in Step 3 to generate molten ablation material with nanoscale features. At the same time, turn on the auxiliary air blowing system and control the directional airflow generated by the air blowing port of the auxiliary air blowing system to blow towards the ablation material. The directional airflow is used to remove the dust generated during the processing in time, so as to avoid its redeposition and interference with the subsequent laser action. Finally, a micro-nano structure with controllable morphology is formed on the surface of the energetic material.

[0013] Step 6: Post-process and characterize the energetic material crystal sample with micro-nano structures on its surface to complete the preparation of the energetic material surface micro-nano structures.

[0014] In the above scheme, when the auxiliary air blowing system is set up, the axis of the air blowing port of the auxiliary air blowing system is perpendicular to the surface of the energetic material crystal sample.

[0015] Furthermore, the directional airflow generated by the air outlet of the controlled auxiliary air blowing system blows towards the ablated material in the following specific manner: the air outlet of the controlled auxiliary air blowing system is 1~1.5cm away from the surface of the energetic material crystal sample. When the directional airflow generated by the air outlet reaches the surface of the energetic material crystal sample, it can completely cover and effectively remove the molten ablated material in the processing area.

[0016] Further, in step 3, the laser wavelength is 1032nm, the pulse width is 299fs, the laser power is 0.1~0.3w, and the repetition frequency is 25~200kHz; the scanning path adopts a linear, grid, or custom path according to the structural design, the scanning method is single or multiple scans, the scanning interval is 50~100nm, the scanning speed is 0.0001~1mm / s, and the number of repeated scans is 1~20 times.

[0017] In a specific embodiment of the present invention, the laser wavelength is 1032nm, the pulse width is 299fs, the laser power is 0.15w, and the repetition frequency is 100kHz; the scanning method is linear scanning, the scanning interval is 50nm, the scanning speed is 0.005mm / s, and the scanning is repeated once.

[0018] Furthermore, in step 4, the objective lens of the microscope focusing system has a magnification of 2 to 50 times and a numerical aperture of 0.05 to 0.65. The processing range can be controlled by linkage between the objective lens field of view and the scanning system. The positioning accuracy of the high-speed precision scanning system is greater than 1 μm.

[0019] In a specific embodiment of the present invention, the objective lens of the microscope focusing system has a magnification of 50x, a numerical aperture of 0.65, and a processing field of view of 2mm × 2mm.

[0020] Further, in step 5, the diameter of the air blowing port of the auxiliary air blowing system is 5 mm; the air pressure of the directional airflow is 1-5 kPa and the temperature is 20-25 °C; the distance between the air blowing port of the auxiliary air blowing system and the surface of the energetic material crystal sample is controlled to be 1-1.5 cm; the feature size of the micro / nano structure is 1-10 μm and the structure depth is 1-10 μm.

[0021] In a specific embodiment of the present invention, the diameter of the air blowing port of the auxiliary air blowing system is 5 mm; the air pressure of the directional airflow is 3 kPa and the temperature is 25 °C; the distance between the air blowing port of the auxiliary air blowing system and the surface of the energetic material crystal sample is controlled to be 1.2 cm; the feature size of the micro / nano structure is 2.8 μm and the structure depth is 4.5 μm.

[0022] To achieve the goal of fabricating multiple micro / nano structures on energetic material crystal samples, based on the above scheme, the following steps are also included between steps 5 and 6:

[0023] Step A: Move the unprocessed area of ​​the energetic material crystal sample obtained in Step 5 horizontally below the microscope focusing system (3) and position it at the focal length of the microscope objective.

[0024] Step B: Using the methods in Steps 4 and 5, the unprocessed area is scanned and processed to form micro-nano structures with specific morphology and size on the surface of the energetic material crystal sample;

[0025] Step C, repeating steps A and B, completes the fabrication of micro / nano structures with different structural features within a specific small area on the sample surface, or realizes the preparation of multiple regions with specific structures.

[0026] Step 6 specifically involves cleaning, drying, and characterizing the morphology of the energetic material crystal sample whose surface has undergone micro-defect processing in all target areas, thereby completing the preparation of controllable micro-defects on the surface of the energetic material crystal.

[0027] The beneficial effects of this invention include:

[0028] 1. This invention provides a method for preparing controllable micro-defects on the surface of energetic material crystals based on femtosecond laser micromachining. This method optimizes the wavelength, pulse width, laser power, and repetition frequency parameters of the femtosecond laser, utilizes a high-speed precision scanning system to achieve precise positioning and path control of the laser focusing position, and combines this with an auxiliary air blowing system to promptly remove surface dust during processing. This allows for the formation of micro-defect structures with regular morphology and controllable size on the surface of energetic material crystals, with good process repeatability. Specifically, the control of crystal crack damage is mainly achieved by adjusting laser parameters such as power, frequency, and spot size, in coordination with the scanning parameters of the high-speed precision three-dimensional scanning system. This method avoids the alteration of the material's chemical composition caused by traditional doping methods, providing a new high-precision, non-contact processing approach for the functional surface modification of energetic materials. The prepared micro-defect structures can modulate the local optical field distribution under laser irradiation, enhancing the localization effect of energy deposition. Furthermore, by controlling the morphology, size, and density of the micro-defects, the number and temperature of detonation hotspots within the energetic material can be influenced, ultimately achieving quantitative control of the laser detonation energy threshold (i.e., laser detonation sensitivity). This provides an effective structural basis for establishing a quantitative relationship between micro-defect characteristics and laser detonation sensitivity. During this process, due to the explosive nature of energetic material crystals, the preparation of micro-defects places extremely high demands on laser parameters: too low an energy level will prevent the formation of the desired defect array, while too high an energy level will easily induce micro-explosions and propagating cracks. This method, through precise control of laser and scanning parameters, achieves the controllable and safe preparation of micro-defect arrays on the surface of energetic materials.

[0029] 2. The femtosecond laser micromachining method described in this invention demonstrates high process adaptability and controllability for the successful fabrication of micro-defects in RDX energetic materials. By precisely controlling laser parameters and the processing path, this method can form micro-defects with controllable morphology, size, and depth on the surface of RDX crystals while maintaining the integrity of the crystal structure. This provides a repeatable and designable experimental basis for studying the control mechanism of micro-defects on the laser-induced detonation behavior of energetic materials. In principle, this method can be extended to other energetic elemental explosive crystals such as HMX and PETN, providing a universal precision processing means for the active control of the laser-induced detonation performance of energetic materials and the functionalized surface modification. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a femtosecond laser micromachining system processing an energetic material crystal sample in an embodiment of the present invention;

[0031] Figure 2 These are 3D confocal microscopy morphology characterization images of typical single micro-defects prepared on the surface of energetic material crystals using the method of this invention;

[0032] Figure 3 This is a 3D confocal microscope morphology characterization of a typical single micro-defect prepared on the surface of an energetic material crystal without the use of an auxiliary air blowing system.

[0033] Figure 4 This is a 3D confocal microscope image of the morphology of a typical single micro-defect prepared on the surface of an energetic material crystal using excessively low laser energy.

[0034] Figure 5 This is a 3D confocal microscope morphology characterization image of a typical single micro-defect prepared on the surface of an energetic material crystal using excessively high laser energy.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1- Femtosecond laser, 2- Mirror system, 3- Microscope focusing system, 4- Auxiliary air blowing system, 5- Energetic material crystal sample, 6- High-speed precision three-dimensional scanning system. Detailed Implementation

[0037] The technical solution for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] A method for constructing controllable micro-defects on the surface of energetic material crystals based on femtosecond laser micromachining includes the following steps:

[0039] Step 1: Assemble the femtosecond laser micromachining device; such as Figure 1 As shown, the femtosecond laser micromachining device includes a femtosecond laser 1, a mirror system 2, a micro-focusing system 3, an auxiliary air blowing system 4, and a high-speed precision three-dimensional scanning system 6, arranged sequentially along the laser beam path. In this embodiment, the micro-focusing system 3 is a high numerical aperture microscope objective.

[0040] Step 2: Select energetic material crystal sample 5; in this embodiment, sample 5 is an RDX single crystal, while in other embodiments it can be an HMX crystal or a PETN crystal.

[0041] Step 3: Preset the processing parameters of the femtosecond laser 1 and the scanning parameters of the high-speed precision 3D scanning system; the processing parameters include laser wavelength, pulse width, laser power and repetition frequency, and the scanning parameters include processing path, processing method, scanning interval, scanning speed and number of processing repetitions.

[0042] The laser wavelength is 1032 nm, the pulse width is 299 fs, the laser power is 0.1–0.3 W, and the repetition frequency is 25–200 kHz. The processing path is point-like or short linear, the processing method is single-pulse or multi-pulse fixed-point irradiation, the scanning interval is set according to the defect distribution requirements, the scanning speed is adjusted according to the processing method, and the number of repeated processing cycles is 1–10. In this embodiment, the laser wavelength is 1032 nm, the pulse width is 299 fs, the laser power is 0.15 W, the repetition frequency is 100 kHz, the processing method is single-pulse fixed-point irradiation, and the number of repeated processing cycles is 1.

[0043] Step 4: Place the energetic material crystal sample 5 on a high-precision three-dimensional translation sample stage, and adjust the sample stage to move the energetic material sample directly below the microscope objective and at the focal plane of the microscope objective. Turn on the femtosecond laser 1 and the high-speed precision three-dimensional scanning system 6, so that the femtosecond laser 1 outputs a femtosecond laser corresponding to the processing parameters in step 3. The femtosecond laser passes through the mirror system 2 and is focused onto the surface of the energetic material sample by the microscope objective to form a focused spot. The microscope objective has a magnification of 5 to 50 times and a numerical aperture of 0.05 to 0.65. In this embodiment, the microscope objective has a magnification of 50 times and a numerical aperture of 0.65.

[0044] Step 5: Turn on the high-speed precision 3D scanning system and focus the light spot to perform targeted irradiation processing on the selected position on the surface of the energetic material crystal sample according to the scanning parameters in Step 3, producing micro-area ablation; simultaneously, turn on the auxiliary air blowing system 4, controlling the distance between the air blowing port of the auxiliary air blowing system 4 and the surface of the energetic material crystal sample to be 1.2 cm, with the axis of the air blowing port perpendicular to the sample surface, and when the clean airflow generated by the air blowing port reaches the sample surface, it can effectively cover and remove the dust generated in the processing area, ultimately forming a single micro-defect with a clear morphology and controllable size on the surface of the energetic material crystal sample. Its typical morphological characteristics are shown in […]. Figure 2 In this embodiment, the diameter of the air outlet of the auxiliary air blowing system 4 is 5mm, the air pressure of the clean airflow is 3kPa, and the temperature is 20℃.

[0045] Depend on Figure 2 As can be seen, the micro-defect has clear edges and a regular geometric morphology, with a characteristic size of approximately 2.8 μm and a depth of approximately 4.5 μm, and no visible cracks in the surrounding area. This micro-defect structure with controllable morphology and no collateral damage is the key physical basis for effectively controlling the laser-induced detonation sensitivity of energetic material crystals, and it is also the core feature that distinguishes this method from other femtosecond laser processing techniques that may cause crystal damage.

[0046] It should be noted that when performing femtosecond laser point irradiation without using the auxiliary air blowing system 4 to remove dust from the processing area, the micron and submicron-sized dust generated during the processing will rapidly accumulate in and around the processing area. This accumulated dust will form a non-uniform shielding layer, preventing subsequent laser pulses from being effectively focused and applied to the intrinsic surface of the energetic material crystal. This results in energy deposition position drift, uncontrollable depth of action, and may induce localized overheating due to non-uniform absorption and scattering of energy within the dust layer, leading to problems such as… Figure 3 The diagram shows uncontrolled damage such as microcracks. This damage not only disrupts the target morphology of the micro-defects but also introduces unpredictable structural uncertainties.

[0047] The present invention, under the real-time action of the directional and clean airflow generated by the air blowing port 4 of the auxiliary air blowing system, can promptly and effectively blow away the dust generated by each processing pulse from the laser action point, thereby always maintaining the laser focus precisely acting on the preset position of the energetic material crystal. This ensures that the energy of each laser pulse is directly and efficiently deposited on the fresh material surface, achieving precise control of the ablation process. Under these optimized conditions, not only are processing uncertainties caused by dust shielding and redeposition effects avoided, but the expansion of the heat-affected zone and the accumulation of thermal stress are also significantly suppressed, ultimately achieving the desired result. Figure 2The image on the right shows a high-quality single micro-defect structure with a regular morphology, clear edges, and no accompanying cracks. This structure provides a reliable foundation for subsequent research on the precise control of micro-defects on laser-initiated detonation behavior.

[0048] It should also be noted that energetic material crystals possess explosive properties, making them extremely sensitive to femtosecond laser micromachining parameters. If the laser energy is too low, it is difficult to form a complete and effective defect structure. For example... Figure 4 As shown, when the laser energy drops to 0.11 W, although the initial shape of defects is visible on the surface and no propagating cracks occur, the defect morphology is incomplete and the depth is insufficient, failing to meet the preset requirements for the micro-defect array. Conversely, excessively high energy can easily trigger micro-explosions and lead to propagating cracks. Figure 5 As shown, when the laser energy is increased to 0.17 W, although defects with complete morphology can be fabricated, a large number of propagating cracks appear around the defects, causing crystal damage. Therefore, precise control of laser energy is crucial for achieving high-quality micro-defect array fabrication.

[0049] Step 6: Remove the energetic material crystal sample with controllable micro-defects on its surface from the high-precision three-dimensional translation sample stage, and gently blow its surface with a dry, clean inert gas (such as high-purity nitrogen) to remove loose dust that may be attached to the sample surface and inside the micro-defects, thus completing the preparation of the energetic material crystal surface micro-defects.

[0050] It should be noted that, in other embodiments, to address the need to prepare multiple micro-defects on the surface of a single energetic material crystal sample, the following steps are included between step 5 and step 6:

[0051] Step A: Using a high-precision three-dimensional translation sample stage, move the next processing area of ​​the energetic material crystal sample processed in Step 5 to directly below the microscope objective and position it at the focal plane of the microscope objective.

[0052] Step B: Process the region using the methods in Steps 4 and 5 to form micro-defects with a preset morphology and size on the surface of the energetic material crystal sample again;

[0053] Step C: Repeat steps A and B until all preset micro-defects are prepared on the surface of the energetic material crystal sample. At this point, step 6 specifically involves: removing the energetic material crystal sample with multiple controllable micro-defects from the sample stage and gently purging its surface with a dry, clean inert gas to complete the preparation of multiple micro-defects on the surface of the energetic material crystal.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining, characterized in that, Includes the following steps: Step 1: Construct a femtosecond laser micromachining device; the femtosecond laser micromachining device includes a femtosecond laser (1), a mirror system (2), a microscope focusing system (3), an auxiliary air blowing system (4), and a high-speed precision three-dimensional scanning system (6) arranged sequentially along the laser optical path; Step 2: Select energetic material crystal samples (5); Step 3: Preset the processing parameters of the femtosecond laser (1), including laser wavelength, pulse width, laser power and repetition frequency; preset the scanning parameters of the high-speed precision three-dimensional scanning system (6), including scanning path, scanning mode, scanning spacing, scanning speed and number of repeated scans; Step 4: Place the energetic material crystal sample (5) processed in Step 2 below the microscope focusing system (3) and at the focal length position of the microscope objective; turn on the femtosecond laser (1) so that the femtosecond laser (1) outputs a femtosecond laser corresponding to the processing parameters in Step 3. The femtosecond laser passes through the mirror system (2) and is focused onto the surface of the energetic material crystal sample (5) by the microscope focusing system (3) to form a focused spot; Step 5: Turn on the high-speed precision three-dimensional scanning system (6) and make the focused spot scan the surface of the energetic material crystal sample (5) according to the scanning parameters in step 3 to generate a melt ablation material with nanoscale features; at the same time, turn on the auxiliary air blowing system (4) and control the directional airflow generated by the air blowing port of the auxiliary air blowing system (4) to blow towards the ablation material, and finally form a micro-nano structure with controllable morphology on the surface of the energetic material. Step 6: Post-process and characterize the energetic material crystal sample with micro-nano structures on its surface to complete the preparation of the energetic material surface micro-nano structures.

2. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 1, characterized in that: The air blowing port axis of the auxiliary air blowing system (4) is perpendicular to the surface of the energetic material crystal sample (5).

3. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 2, characterized in that: Specifically, the directional airflow generated by the air outlet of the control auxiliary air blowing system (4) blows towards the ablated material: the air outlet of the control auxiliary air blowing system (4) is 1~1.5cm away from the surface of the energetic material crystal sample (5). When the directional airflow generated by the air outlet reaches the surface of the energetic material crystal sample (5), it can completely cover and effectively remove the molten ablated material in the processing area.

4. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 1, characterized in that: In step 3, the laser wavelength is 1032nm, the pulse width is 299fs, the laser power is 0.1-0.3W, and the repetition frequency is 25-200kHz. The scanning path adopts a linear, grid, or custom path according to the structural design. The scanning method is single or multiple scans, the scanning interval is 50-100nm, the scanning speed is 0.0001-1mm / s, and the number of repeated scans is 1-20.

5. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 4, characterized in that: The laser wavelength is 1032nm, the pulse width is 299fs, the laser power is 0.15w, and the repetition frequency is 100kHz; the scanning method is linear scanning, the scanning interval is 50nm, the scanning speed is 0.005mm / s, and the scan is repeated once.

6. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 1, characterized in that: In step 4, the objective lens of the microscope focusing system (3) has a magnification of 2 to 50 times and a numerical aperture of 0.05 to 0.65; the positioning accuracy of the high-speed precision scanning system is greater than 1 μm.

7. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 6, characterized in that: The objective lens of the microscope focusing system (3) has a magnification of 50x, a numerical aperture of 0.65, and a processing field of view of 2mm×2mm.

8. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 1, characterized in that: In step 5, the diameter of the air blowing port of the auxiliary air blowing system (4) is 5 mm; the air pressure of the directional airflow is 1-5 kPa and the temperature is 20-25 °C; the distance between the air blowing port of the auxiliary air blowing system (4) and the surface of the energetic material crystal sample (5) is controlled to be 1-1.5 cm; the characteristic size of the micro-nano structure is 1-10 μm and the structural depth is 1-10 μm.

9. The method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to claim 8, characterized in that: The diameter of the air blowing port of the auxiliary air blowing system (4) is 5 mm; the air pressure of the directional airflow is 3 kPa and the temperature is 25 °C; the distance between the air blowing port of the auxiliary air blowing system (4) and the surface of the energetic material crystal sample (5) is controlled to be 1.2 cm; the feature size of the micro-nano structure is 2.8 μm and the structure depth is 4.5 μm.

10. A method for preparing energetic material crystal micro-defects based on femtosecond laser micromachining according to any one of claims 1-9, characterized in that: The following steps are also included between steps 5 and 6: Step A: Move the unprocessed area of ​​the energetic material crystal sample obtained in Step 5 horizontally below the microscope focusing system (3) and position it at the focal length of the microscope objective. Step B: Using the methods in Steps 4 and 5, the unprocessed area is scanned and processed to form micro-nano structures with specific morphology and size on the surface of the energetic material crystal sample; Step C, repeating steps A and B, completes the fabrication of micro / nano structures with different structural features within a specific small area on the sample surface, or realizes the preparation of multiple regions with specific structures.

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