System and method for ultrafast laser welding of sapphire

Abstract

The invention belongs to the field of laser welding, and particularly discloses an ultrafast sapphire laser welding system and method.The system comprises an ultrafast laser device, a beam expanding collimating mirror, a reflector assembly and a galvanometer assembly which are sequentially arranged in the laser transmission direction, and the ultrafast laser device is used for emitting ultrafast laser beams; the beam expanding and collimating mirror is used for conducting beam expanding and collimating on the ultrafast laser beam to obtain a collimated ultrafast laser beam, the collimated ultrafast laser beam is reflected by the reflector assembly and then enters the galvanometer to form a focused laser beam, the galvanometer drives the focused laser beam to scan the sapphire to be welded according to a preset path, and therefore ultrafast laser welding of the sapphire is achieved. According to the method, the scanning speed can be effectively increased to achieve rapid welding, meanwhile, the focus positioning precision and the requirement for the to-be-welded sapphire surface are lowered, and the machining efficiency is greatly improved again.

Description

Technical Field

[0001] This application belongs to the field of laser welding, and more specifically, relates to a system and method for ultrafast laser welding of sapphire. Background Technology

[0002] The rapid development of smart wearable devices, high-end optical components, and semiconductor manufacturing technologies has placed higher demands on the comprehensive performance of materials. Traditional glass and plastic materials have significant limitations in terms of wear resistance, light transmittance, and high-temperature resistance, making it difficult to meet long-term usage requirements. Sapphire (α-Al₂O₃ single crystal), with its high hardness (Mohs hardness 9), excellent optical transparency (visible light transmittance >90%), high-temperature resistance (melting point approximately 2050℃), and chemical stability, has become an ideal alternative to traditional materials. Currently, sapphire is widely used in smartwatch crystals, high-end camera protective covers, precision optical windows, and LED substrates, but its high processing cost and brittleness still hinder its further promotion.

[0003] Currently, the mainstream processes for joining multiple sapphire crystals in the industrial field include solder bonding, organic adhesive bonding, and high-temperature fusion welding. Solder bonding is prone to chemical compatibility failure due to significant differences in the thermal expansion coefficients of the interface materials; adhesive bonding is limited by the thermal stability (long-term operating temperature is usually below 150℃) and weather resistance of organic materials, and is prone to interface aging in humid and hot environments; while high-temperature fusion welding can achieve direct bonding between sapphire crystals, it requires a high-temperature process of 800℃ to 1200℃, which can cause dimensional deformation of the weldment (deformation rate can reach 0.3% to 0.8%) and residual stress concentration. These traditional processes have revealed technical bottlenecks in high-end manufacturing fields such as precision optical devices and micro-sensors, including insufficient connection strength (shear strength generally below 100MPa), deterioration of optical performance (transmittance decrease of 3% to 8%), and poor process compatibility, making it difficult to meet the urgent needs of modern industry for high-precision and high-reliability connections.

[0004] Addressing the technical bottlenecks of sapphire bonding, ultrafast laser welding technology exhibits significant advantages, including: (1) low heat input and precise energy control: femtosecond / picosecond ultrafast laser pulses (pulse width <10 -12(1) Energy can be localized and deposited on the material interface in a very short time. The width of the heat-affected zone (HAZ) is only on the micrometer level, which effectively suppresses stress concentration and microcrack propagation caused by thermal expansion difference in sapphire. (2) Molecular bonding and high-strength interface: Laser-induced high temperature and high pressure plasma can promote atomic diffusion between sapphire and substrate materials such as metal / ceramics, forming covalent / ionic bonds. The shear strength can reach 3-5 times that of traditional adhesives, meeting the requirements of extreme load environment. (3) Optical performance retention and no impurity introduction: The ultrafast laser wavelength (such as 1030nm) matches the sapphire band gap (8.8eV), avoiding material discoloration caused by light absorption; non-contact processing eliminates mechanical contact pollution, ensuring that the transmittance loss of optical components is <0.5%. (4) Adaptability to complex structures: Through beam shaping and dynamic focusing technology, precision welding of complex structures such as three-dimensional curved surfaces and nanoscale microchannels can be achieved, breaking through the limitations of traditional processes on planar connections. (5) Environmental protection and low cost potential: No vacuum environment or chemical additives are required, the single-pass welding time is <100μs, and the equipment energy consumption is reduced by more than 60%, making it suitable for large-scale production. These characteristics provide key technical support for the innovative applications of sapphire in high-power laser windows, semiconductor packaging, and aerospace sensors. However, existing ultrafast laser welding systems generally use a displacement platform to move the sapphire to be welded to achieve laser scanning, which results in slow scanning speed and low welding efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a system and method for ultrafast laser welding of sapphire, aiming to solve the problem of low welding efficiency in existing ultrafast laser welding of sapphire.

[0006] According to one aspect of this application, a system for ultrafast laser welding of sapphire is provided, specifically including an ultrafast laser, a beam expander and collimator, a reflector assembly, and a galvanometer assembly arranged sequentially along the laser transmission direction. The ultrafast laser is used to emit an ultrafast laser beam; the beam expander and collimator is used to expand and collimate the ultrafast laser beam to obtain a collimated ultrafast laser beam; the collimated ultrafast laser beam is reflected by the reflector assembly and enters the galvanometer to form a focused laser beam; the galvanometer drives the focused laser beam to perform single-layer, multi-channel, multiple scans of the sapphire to be welded along a preset path, thereby achieving ultrafast laser welding of sapphire.

[0007] Compared with the prior art, the technical solution conceived in this application can effectively improve the scanning speed to achieve rapid welding by using a galvanometer assembly instead of a microscope objective to perform rapid scanning of the sapphire to be welded, and by combining it with a single-layer multi-pass multiple-scanning strategy.

[0008] As a further preferred embodiment, the galvanometer assembly includes an X-scanning galvanometer, a Y-scanning galvanometer, and a focusing field mirror arranged sequentially along the light propagation direction. The galvanometer assembly also includes a motor. The X-scanning and Y-scanning galvanometers are used to control the deflection of the collimated ultrafast laser beam in the X-axis and Y-axis directions, respectively, before feeding it into the focusing field mirror to form a focused laser beam, thereby adjusting the welding position of the focused laser beam on the sapphire to be welded. The motor is used to drive the X-scanning galvanometer, Y-scanning galvanometer, and focusing field mirror to move up and down along the Z-axis, thereby adjusting the focusing position of the focused laser beam on the sapphire to be welded.

[0009] As a further preferred embodiment, the ultrafast laser welding system for sapphire also includes a displacement platform for placing the sapphire to be welded and moving it along the X, Y, and Z axes.

[0010] As a further preferred embodiment, the displacement platform is provided with a clamping element for clamping the sapphire to be soldered, causing it to exhibit colored interference fringes.

[0011] As a further preferred embodiment, the reflector assembly includes two or more reflectors.

[0012] As a further preferred embodiment, the ultrafast laser has a pulse width of 0.4 ps to 2.0 ps and a repetition frequency of 25 kHz to 1000 kHz.

[0013] According to another aspect of this application, a method for ultrafast laser welding of sapphire using the above-described system is provided, specifically as follows: S1 stacks two sapphire stones to obtain a sapphire stone to be soldered, and then applies pressure to the sapphire stone to be soldered so that colored interference fringes appear at the interface of the two sapphire stones. S2 emits an ultrafast laser beam from an ultrafast laser and forms a focused laser beam. Then, a galvanometer assembly drives the focused laser beam to scan the sapphire to be welded along the welding path, thereby achieving ultrafast laser welding of sapphire.

[0014] As a further preferred option, the number of scans is 30 to 80.

[0015] As a further preferred option, the pulse energy of the ultrafast laser beam is 18.15 μJ to 32.65 μJ, and the scanning speed is 500 mm / s to 900 mm / s.

[0016] As a further preferred embodiment, each weld seam includes multiple scanning lines, with the spacing between adjacent scanning lines being 20μm to 60μm.

[0017] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages: 1. This application uses a galvanometer assembly instead of a microscope objective to rapidly scan the sapphire to be welded, and combines it with a single-layer multi-pass multiple-scan strategy, which can effectively improve the scanning speed to achieve rapid welding. At the same time, the use of the galvanometer assembly greatly reduces the requirements for the accuracy of the focal point positioning and the surface of the sapphire to be welded. In the subsequent welding process, it is only necessary to clean the sapphire surface, apply vertical pressure, and use atmospheric pressure to reduce the gap between the two sapphire pieces before welding. Welding can be carried out without the need for clamping fixtures, which further greatly improves the processing efficiency. 2. In particular, by optimizing the structure of the galvanometer assembly, this application enables adjustment in the X, Y, and Z axes, thereby adjusting the focusing position of the focused laser beam on the sapphire to be welded and improving processing efficiency; 3. In addition, this application optimizes the parameters in the welding process, including the number of scans, laser energy, scanning speed and the spacing between adjacent scan lines, which can effectively reduce the heat-affected zone and thermal distortion, and improve the sapphire welding effect. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the ultrafast laser welding sapphire system provided in the embodiments of this application; Figure 2 This is a schematic diagram of the galvanometer assembly in the ultrafast laser welding sapphire system provided in the embodiments of this application; Figure 3 This is a schematic diagram of the movement of the galvanometer assembly along the Z-axis in the ultrafast laser welding sapphire system provided in the embodiments of this application; Figure 4 This is a schematic diagram of a welding path and a partially enlarged view thereof provided in one embodiment of this application; Figure 5 This is a schematic diagram of the welding path and a partial enlarged view provided in another embodiment of this application.

[0019] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Ultrafast laser, 2-Ultrafast laser beam, 3-Beam expander and collimator, 4-Collimating ultrafast laser beam, 5-First reflecting mirror, 6-Second reflecting mirror, 7-Galvanometer assembly, 71-X-scanning galvanometer, 72-Y-scanning galvanometer, 73-Focusing field mirror, 8-Sapphire crystal to be welded, 9-Focused laser beam, 10-Upper sapphire crystal, 11-Lower sapphire crystal, 12-Welding path, 13-Displacement platform. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] like Figure 1 As shown, according to one aspect of this application, a system for ultrafast laser welding of sapphire is provided, specifically including an ultrafast laser 1, a beam expander and collimator 3, a reflector assembly, and a galvanometer assembly 7 arranged sequentially along the laser transmission direction. The ultrafast laser 1 is used to emit an ultrafast laser beam 2; the beam expander and collimator 3 is used to expand and collimate the ultrafast laser beam 2 to obtain a collimated ultrafast laser beam 4, which is reflected by the reflector assembly and enters the galvanometer assembly 7 to form a focused laser beam 9. The galvanometer assembly 7 drives the focused laser beam 9 to perform single-layer multi-channel multiple scans of the sapphire to be welded according to a preset path, thereby realizing ultrafast laser welding of sapphire.

[0022] This application uses a galvanometer assembly 7 instead of a microscope objective to rapidly scan the sapphire crystal 8 to be welded. Because the scanning speed of the galvanometer assembly 7 is much faster than that of the displacement platform when using a microscope, this application can effectively accelerate the welding speed. Furthermore, combined with a single-layer, multi-pass, multiple-scanning strategy, it can achieve rapid welding. Simultaneously, the use of the galvanometer assembly 7 significantly reduces the precision of focal point positioning and the requirements for the sapphire surface. Only cleaning the sapphire surface and applying vertical pressure are needed; atmospheric pressure is then used to reduce the gap between the two sapphire crystals before welding. Welding can be performed without the need for clamping fixtures, further significantly improving processing efficiency. Compared with traditional sapphire bonding systems, this application offers advantages such as high connection strength, high precision, flexibility, non-contact operation, minimal heat-affected zone and thermal distortion, fewer workpiece shape restrictions, and single-step operation.

[0023] Furthermore, such as Figure 2 , 3 As shown, the galvanometer assembly 7 includes an X-scanning galvanometer 71, a Y-scanning galvanometer 72, and a focusing field mirror 73 arranged sequentially along the light propagation direction. The galvanometer assembly 7 also includes a motor. The X-scanning galvanometer 71 and the Y-scanning galvanometer 72 are used to control the deflection of the collimated ultrafast laser beam 4 in the X-axis and Y-axis directions, respectively, and then fed into the focusing field mirror 73 to form a focused laser beam 9, thereby adjusting the welding position of the focused laser beam 9 on the sapphire to be welded. The motor is used to drive the X-scanning galvanometer 71, the Y-scanning galvanometer 72, and the focusing field mirror 73 to move up and down along the Z-axis, thereby adjusting the focusing position of the focused laser beam 9 on the sapphire to be welded.

[0024] Furthermore, the ultrafast laser welding system for sapphire also includes a displacement platform 13, which is used to place the sapphire to be welded and move it along the X, Y, and Z axes. The displacement platform 13 moves the sapphire to be welded 8 to adjust its position.

[0025] Furthermore, before welding, a force perpendicular to the sapphire to be welded needs to be applied to the sapphire to be welded, so that colored interference fringes appear at the interface of the two sapphire pieces. In order to facilitate the application of vertical pressure, a clamping component is provided on the displacement platform 13 to clamp the sapphire to be welded and apply a force perpendicular to the sapphire to be welded, so that colored interference fringes appear on the two pieces.

[0026] Furthermore, the mirror assembly includes two or more mirrors to adjust the collimated ultrafast laser beam 4 so that it enters the galvanometer assembly 7. For example... Figure 1 As shown, in a preferred embodiment of this application, the reflector assembly includes a first reflector 5 and a second reflector 6. The collimated ultrafast laser beam 4 enters the galvanometer assembly 7 after being reflected by the first reflector 5 and the second reflector 6.

[0027] Furthermore, the pulse width of the ultrafast laser 1 is 0.4 ps to 2.0 ps, ​​and the repetition frequency is 25 kHz to 1000 kHz. When the pulse width is too large, the heat diffusion time increases, resulting in a greater proportion of heat conduction during energy deposition. The molten pool duration increases, the heat-affected zone enlarges, and spatter can form in the weld area. When the repetition frequency is too low, the long pulse interval allows sufficient time for the heat generated by the previous pulse to diffuse and dissipate into the surrounding material. The heat accumulation effect is small, and the heat-affected zone is close to that of a single pulse, failing to form an effective weld. When the repetition frequency is too high, the heat generated by the previous pulse has not completely dissipated before the energy of subsequent pulses is superimposed, leading to significant heat accumulation, increased average temperature, larger molten pool size, and expanded heat-affected zone. This negates the low-heat advantage of the ultrafast laser, leading to the formation of hot cracks and a decline in weld quality.

[0028] According to another aspect of this application, a method for ultrafast laser welding of sapphire using the above-described system is provided, specifically as follows: S1 performs ultrasonic cleaning on the sapphire and then dries it to ensure that the sapphire surface is free of oil and other impurities. Then, the upper sapphire 10 and the lower sapphire 11 are stacked to obtain the sapphire 8 to be welded. Pressure is applied to the sapphire 8 to be welded so that colored interference fringes appear at the interface of the two sapphires. S2 emits an ultrafast laser beam 2 through an ultrafast laser 1 and forms a focused laser beam 9. Then, the galvanometer assembly 7 drives the focused laser beam 9 to perform single-layer multi-pass multiple scans along the welding path 12, thereby realizing ultrafast laser welding of sapphire.

[0029] Furthermore, the welding path 12 can be designed as needed. In one embodiment of this application, such as... Figure 4 As shown, welding path 12 includes a weld seam composed of multiple parallel and spaced scan lines; in another embodiment of this application, as... Figure 3As shown, welding path 12 includes four intersecting welds, each weld comprising multiple parallel, spaced scanning lines. More preferably, the spacing between adjacent scanning lines is 20 μm to 60 μm. When the spacing between adjacent scanning lines is less than 20 μm, the overlapping area between the scanning lines is too large, causing excessive concentration of laser energy in one area, resulting in localized overheating and easily leading to defects such as porosity and cracks, while also reducing welding efficiency. When the spacing between adjacent scanning lines is greater than 60 μm, the overlapping area between adjacent scanning lines is small, resulting in uneven heat distribution in the welding area, easily leading to incomplete fusion defects, poor weld continuity and density, and affecting welding quality.

[0030] Furthermore, the number of scans is 30 to 80. The first 10 to 20 scans gradually reduce the gap between the sapphire crystals, forming a complete and continuous weld. Subsequent scans gradually enlarge the weld, increasing the bonding strength of the sapphire crystals. The method provided in this application is a bonding welding process that eliminates the need for prolonged dwell time in localized areas, effectively shortening processing time.

[0031] Furthermore, the pulse energy of the ultrafast laser beam 2 ranges from 18.15 μJ to 32.65 μJ. Too low a pulse energy results in limited heat provided by the laser beam, insufficient melting of the welding material, leading to shallow weld depth, narrow weld width, weak weld, and low weld strength. Conversely, too high a pulse energy can cause over-melting or even vaporization of the material, easily resulting in defects such as spatter, weld overheating, and hot cracking, affecting the mechanical properties and appearance quality of the weld. The scanning speed ranges from 500 mm / s to 900 mm / s. Too low a scanning speed results in excessive laser dwell time in the welding area, excessive heat input, and overheating of the weld and heat-affected zone, easily leading to hot cracking. Too high a scanning speed results in insufficient laser dwell time in the welding area, insufficient energy absorption by the material, and insufficient melting, leading to shallow weld depth, narrow weld width, and weak weld. The pulse energy interacts with the number of scans, scan speed, and spacing between adjacent scan lines, ensuring sufficient energy for the welding area while maintaining welding quality and preventing excessive heat accumulation to avoid local overheating.

[0032] The technical solutions provided in this application will be further described below with reference to specific embodiments.

[0033] Example 1 An ultrafast laser with an output wavelength of 1030 nm, a pulse width of 0.4 ps, a maximum output power of 70 W, and a repetition frequency of 25 kHz to 1000 kHz was used to weld two 1 mm thick sapphire crystals together. The two sapphire crystals were initially stacked with a gap of approximately 10 μm, which was reduced to 2 μm to 5 μm after applying a perpendicular force. The ultrafast laser was focused on the bonding surface of the two sapphire crystals, with a pulse repetition frequency of 200 kHz, a single pulse energy of 23.2 μJ, 60 scans, a scan line spacing of 50 μm, and a scanning speed of 500 mm / s. Figure 4 The path is shown. A single-layer, multi-pass, multiple-scan strategy was adopted. Welding results show that the sapphire melts uniformly at the weld, with a maximum shear strength of 100 MPa, and no damage marks are found on the sapphire surface.

[0034] Example 2 Based on the above embodiment 1, the following is adopted Figure 5 Replace with grid-like path Figure 4 A straight path was used to encapsulate and solder the sapphire. The soldering results showed that the sapphire melted evenly at the weld, the weld was complete and continuous, the airtightness was good, and there were no signs of damage on the sapphire surface.

[0035] Example 3 An ultrafast laser with an output wavelength of 1030 nm, a pulse width of 1.0 ps, ​​a maximum output power of 70 W, and a repetition frequency of 25 kHz to 1000 kHz was used to weld two 1 mm thick sapphire crystals together. The two sapphire crystals were initially stacked with a gap of approximately 10 μm, which was reduced to 2 μm to 5 μm after applying a perpendicular force. The ultrafast laser was focused on the bonding surface of the two sapphire crystals, with the pulse repetition frequency set to 1000 kHz, the single pulse energy to 18.15 μJ, the number of repeated scans to 30, the scan line spacing to 60 μm, and the scanning speed to 700 mm / s. Figure 4 The path is shown. A single-layer, multi-pass, multiple-scan strategy was adopted. Welding results show that the sapphire melts uniformly at the weld, with a maximum shear strength of 70 MPa, and no damage marks are found on the sapphire surface.

[0036] Example 4 An ultrafast laser with an output wavelength of 1030 nm, a pulse width of 2.0 ps, ​​a maximum output power of 70 W, and a repetition frequency of 25 kHz to 1000 kHz was used to weld two 1 mm thick sapphire crystals together. The two sapphire crystals were initially stacked with a gap of approximately 10 μm, which was reduced to 2 μm to 5 μm after applying a perpendicular force. The ultrafast laser was focused on the bonding surface of the two sapphire crystals, with a pulse repetition frequency of 500 kHz, a single pulse energy of 29.9 μJ, 50 repeated scans, a scan line spacing of 30 μm, and a scanning speed of 700 mm / s. Figure 4The path is shown. A single-layer, multi-pass, multiple-scan strategy was adopted. Welding results show that the sapphire melts uniformly at the weld, with a maximum shear strength of 70 MPa, and no damage marks are found on the sapphire surface.

[0037] Example 5 An ultrafast laser with an output wavelength of 1030 nm, a pulse width of 0.4 ps, a maximum output power of 70 W, and a repetition frequency of 25 kHz to 1000 kHz was used to weld two 1 mm thick sapphire crystals together. The two sapphire crystals were initially stacked with a gap of approximately 10 μm, which was reduced to 2 μm to 5 μm after applying a perpendicular force. The ultrafast laser was focused on the bonding surface of the two sapphire crystals, with a pulse repetition frequency of 200 kHz, a single pulse energy of 32.65 μJ, 80 scans, a scan line spacing of 40 μm, and a scanning speed of 900 mm / s. Figure 4 The path is shown. A single-layer, multi-pass, multiple-scan strategy was adopted. Welding results show that the sapphire melts uniformly at the weld, with a maximum shear strength of 60 MPa, and no damage marks are found on the sapphire surface.

[0038] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0039] Furthermore, throughout this specification, references to "an embodiment"; "an embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. Therefore, the appearance of the phrase "in one embodiment;" throughout this specification, and similar language, may, but not necessarily, refer to the same embodiment.

[0040] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A system for ultrafast laser welding of sapphire, characterized in that, The assembly includes an ultrafast laser (1), a beam expander and collimator (3), a reflector assembly, and a galvanometer assembly (7) arranged sequentially along the laser transmission direction. The ultrafast laser (1) is used to emit an ultrafast laser beam (2). The beam expander and collimator (3) is used to expand and collimate the ultrafast laser beam (2) to obtain a collimated ultrafast laser beam (4). The collimated ultrafast laser beam (4) enters the galvanometer assembly (7) after being reflected by the reflector assembly to form a focused laser beam (9). The galvanometer assembly (7) drives the focused laser beam (9) to perform single-layer multi-channel multiple scans on the sapphire (8) to be welded according to a preset path, thereby realizing ultrafast laser welding of sapphire.

2. The system as described in claim 1, characterized in that, The galvanometer assembly (7) includes an X-scanning galvanometer (71), a Y-scanning galvanometer (72), and a focusing field mirror (73) arranged sequentially along the light propagation direction. The galvanometer assembly (7) also includes a motor. The X-scanning galvanometer (71) and the Y-scanning galvanometer (72) are used to control the deflection of the collimated ultrafast laser beam (4) in the X-axis direction and the Y-axis direction, respectively, and then fed into the focusing field mirror (73) to form a focused laser beam (9), thereby adjusting the welding position of the focused laser beam (9) on the sapphire to be welded. The motor is used to drive the X-scanning galvanometer (71), the Y-scanning galvanometer (72), and the focusing field mirror (73) to move up and down along the Z-axis direction, thereby adjusting the focusing position of the focused laser beam (9) on the sapphire to be welded.

3. The system as described in claim 1, characterized in that, The ultrafast laser welding system for sapphire also includes a displacement platform (13), which is used to place the sapphire to be welded and move it along the X-axis, Y-axis and Z-axis.

4. The system as described in claim 3, characterized in that, The displacement platform (13) is provided with a clamping member for clamping the sapphire (8) to be welded so that it produces colored interference fringes.

5. The system as described in claim 1, characterized in that, The mirror assembly includes two or more mirrors.

6. The system according to any one of claims 1 to 5, characterized in that, The ultrafast laser (1) has a pulse width of 0.4 ps to 2.0 ps and a repetition frequency of 25 kHz to 1000 kHz.

7. A method for ultrafast laser welding of sapphire using the system described in any one of claims 1 to 6, characterized in that, Specifically: S1 stacks two sapphire stones to obtain a sapphire stone to be soldered, and then applies pressure to the sapphire stone to be soldered so that colored interference fringes appear at the interface of the two sapphire stones. S2 emits an ultrafast laser beam (2) through an ultrafast laser (1) and forms a focused laser beam (9). Then, the galvanometer assembly (7) drives the focused laser beam (9) to scan the sapphire to be welded (8) along the welding path (12), thereby realizing ultrafast laser welding of sapphire.

8. The method as described in claim 7, characterized in that, The number of scans ranges from 30 to 80.

9. The method as described in claim 7, characterized in that, The pulse energy of the ultrafast laser beam (2) is 18.15 μJ to 32.65 μJ, and the scanning speed is 500 mm / s to 900 mm / s.

10. The method according to any one of claims 7 to 9, characterized in that, Each weld seam consists of multiple scan lines, with the spacing between adjacent scan lines ranging from 20μm to 60μm.

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