Green laser and laser welding machine

Abstract

The invention discloses a green laser and a laser welding machine. The green laser comprises a pumping source, a first reflector, a laser crystal, a polarization beam splitter, a second reflector, a frequency doubling crystal, a telescope lens group and a spectroscope; the pumping source provides pulse pumping light; the laser crystal absorbs the pulse pump light to generate fundamental frequency laser in an infrared band, the fundamental frequency laser enters the polarization beam splitter and is split into P polarized light and S polarized light, the P polarized light is transmitted out of the resonant cavity, and the S polarized light is transmitted in the resonant cavity; and the telescope lens group converges the fundamental frequency laser to the frequency doubling crystal to generate frequency doubling laser of a green light wave band, and the frequency doubling laser is transmitted by the spectroscope and then is output. The green laser is used for spot welding of high-reflection materials such as copper and aluminum, the maximum single pulse energy can reach 5 J, the maximum peak power is 2 kW, the pulse width ranges from 0.05 ms to 5 ms, the problem of low absorption of the high-reflection materials to laser in the 1-micron wave band is solved, and the green laser is an edge tool for precise spot welding of the high-reflection materials.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular, to a green laser and a laser welding machine. Background Art

[0002] Pure copper has advantages such as good ductility, high thermal conductivity, good electrical conductivity, and anti-magnetism, and is widely used in cable electrics and electronic components. In the consumer electronics industry, copper welding has become a relatively common connection method. For example, the welding of copper to copper, aluminum alloy, stainless steel and other materials on mobile phones. At present, the welding of copper sheets mainly uses near-infrared fiber lasers and YAG lasers, and their laser wavelengths are 1060nm - 1070nm. The absorption rate of copper to this wavelength is only 5%. Therefore, higher laser energy density is required when welding copper, resulting in greater impact and thermal deformation of the laser on the metal, and a large amount of spatter is easily generated on the copper surface, leading to current short circuits in electronic components, affecting the appearance of products. At the same time, the reflected laser is extremely easy to damage the optical fiber.

[0003] The surface tension and viscosity of copper are very small compared with stainless steel, so that the formation of the molten pool is extremely unstable. And the surface morphology, welding angle, and absorption wavelength are affected by the type of laser. Research shows that the shorter the laser wavelength, the higher the absorption of copper to it. For green laser with a wavelength of 532nm, the absorption rate of copper to it is close to 40%. The energy efficiency of green laser welding copper will be improved a lot.

[0004] There are various methods for generating green laser. In an ideal state, the most direct method is to generate green laser by using the energy level transition of rare earth ions. However, large-energy green light usually needs to use laser frequency doubling technology to convert near-infrared laser into green light. Compared with short-pulse and ultrashort-pulse lasers, the peak power of long-pulse green laser is low, only in the millijoule level, and it is difficult to obtain high frequency doubling efficiency. Therefore, for a long time in the development of green lasers, there are few research reports on long-pulse green laser welding machines at home and abroad. Summary of the Invention

[0005] An embodiment of the present invention provides a green laser and a laser welding machine. The green laser is used for spot welding of high-reflectivity materials such as copper and aluminum, and realizes high-energy pulsed laser of joule level. Its maximum single-pulse energy can reach up to 5J at most, the maximum peak power is 2kW, and the pulse width is between 0.05ms - 5ms, effectively solving the problem of low absorption of 1μm band laser by high-reflectivity materials, and it is a sharp tool for precision spot welding of high-reflectivity materials.

[0006] According to one aspect of the present invention, a green laser is provided, including a pump source, a first reflector arranged along a first optical axis, a laser crystal, a polarization beam splitter, and a second reflector, a frequency doubling crystal, a telescope lens group, and a beam splitter arranged along a second optical axis. The first optical axis and the second optical axis are parallel;

[0007] The pump source is disposed on one side of the laser crystal, and the pump source is used to provide pulsed pump light to the laser crystal;

[0008] The laser crystal is used to absorb the pulsed pump light and generate fundamental frequency laser in the infrared band. The fundamental frequency laser is transmitted in the resonant cavity formed by the first mirror and the second mirror. The fundamental frequency laser reflected by the first mirror or emitted by the laser crystal is incident on the polarization beam splitter, and is split into P-polarized light and S-polarized light by the polarization beam splitter. The P-polarized light is transmitted by the polarization beam splitter and transmitted out of the resonant cavity. The S-polarized light is reflected by the polarization beam splitter to the beam splitter, and after being reflected by the beam splitter, transmitted through the telescope lens group and the frequency doubling crystal, is incident on the second mirror. After being reflected by the second mirror, it is transmitted in the resonant cavity and transmitted through the beam splitter and then output;

[0009] Wherein, the telescope lens group is used to converge the fundamental frequency laser to the frequency doubling crystal to generate frequency doubling laser in the green light band, and the frequency doubling laser is transmitted through the beam splitter and then output.

[0010] Optionally, the telescope lens group includes a plano-convex lens and a plano-concave lens.

[0011] Optionally, the telescope lens group further includes a base and a six-axis adjustment mount, and the plano-convex lens and the plano-concave lens are fixed on the base through the six-axis adjustment mount.

[0012] Optionally, it further includes an indicating light source, and the indicating light source is located on the side of the first mirror away from the laser crystal. The indicating light source is used to emit indicating light in the visible light band, and the indicating light source is used for the optical path debugging of the green light laser.

[0013] Optionally, it further includes a focusing lens and a coupling optical fiber on the light output side of the beam splitter. The frequency doubling laser is focused by the focusing lens and then coupled into the coupling optical fiber.

[0014] Optionally, a fiber connector is provided on the side of the coupling optical fiber close to the focusing lens.

[0015] Optionally, it further includes an absorbing component disposed on the side of the polarization beam splitter away from the laser crystal, and the absorbing component is used to absorb the P-polarized light.

[0016] Optionally, a total reflection film in the infrared band is provided on the surface of the first reflector close to the laser crystal side, total reflection films in the infrared band and high-transmission films in the green light band are provided on the surfaces of the second reflector close to the frequency doubling crystal side, a total reflection film in the infrared band and a high-transmission film in the green light band are provided on the surface of the beam splitter close to the polarization beam splitter side, and a high-transmission film in the green light band is provided on the side away from the polarization beam splitter.

[0017] Optionally, the polarization beam splitter includes a high-power polarization beam splitting prism or a polarization beam splitting plate. A polarization beam splitting film in the infrared band is provided on the middle inclined surface of the high-power polarization beam splitting prism, and an anti-reflection film in the infrared band is provided on the right-angle surface of the polarization beam splitting prism.

[0018] According to another aspect of the present invention, a laser welding machine is provided, including the above-mentioned green laser.

[0019] In the green laser provided by the embodiment of the present invention, the pump source is arranged on one side of the laser crystal, and the pump source provides pulsed pump light with a millisecond-level pulse width to the laser crystal in a lateral pumping manner; the laser crystal absorbs the pulsed pump light to generate fundamental frequency laser in the infrared band. The polarization beam splitter splits the fundamental frequency laser into P-polarized light and S-polarized light. The P-polarized light is transmitted by the polarization beam splitter and transmitted out of the resonant cavity, and the S-polarized light is reflected by the polarization beam splitter at a 45-degree angle to the beam splitter. It can meet the phase matching condition during frequency doubling, improve the conversion efficiency, and enhance the output stability of the frequency-doubled laser; the S-polarized light is incident on the second reflector after being reflected by the beam splitter, transmitted through the telescope lens group and the frequency doubling crystal, and then reflected by the second reflector and transmitted in the resonant cavity; wherein, the telescope lens group is used to converge the fundamental frequency laser to the frequency doubling crystal to generate frequency-doubled laser in the green light band, and the frequency-doubled laser is output after being transmitted by the beam splitter. By optimizing the design of the entire optical system, the present invention introduces a telescope lens group to reduce the beam, optimizes the beam quality of the fundamental frequency laser, improves the power density of the fundamental frequency laser on the frequency doubling crystal, improves the overall frequency doubling efficiency, uses polarized fundamental frequency laser to meet the phase matching condition of frequency doubling, improves the conversion efficiency, and enhances the output stability of the frequency-doubled laser. On the premise of protecting the frequency doubling crystal from damage, the overall optical-optical conversion efficiency is improved. Its maximum single-pulse energy can reach 5J at most, the maximum peak power is 2kW, and the pulse width is between 0.05ms and 5ms. Compared with the existing green lasers, the single-pulse output energy has achieved a leap from the mJ level to the J level, effectively solving the problem of low absorption of 1μm-band laser by high-reflection materials, and can be applied to laser welding machines for high-reflection materials such as copper and aluminum.

[0020] Meanwhile, since the fundamental frequency light has higher polarization characteristics when passing through a high-power polarization beam splitter (PBS) crystal or a polarization beam splitter, the present invention converts unpolarized light into polarized light by using a high-power PBS crystal or a polarization beam splitter, which can not only withstand high-power fundamental frequency light without being easily damaged, but also obtain S-polarized light with a high degree of polarization. Due to the high degree of polarization of the S-polarized light, the conversion efficiency is significantly improved when passing through the frequency doubling crystal, and green light output with higher energy than the prior art can be achieved.

[0021] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is a schematic structural diagram of a green laser provided by an embodiment of the present invention;

[0024] Figure 2 It is a schematic structural diagram of a telescope lens group provided by an embodiment of the present invention;

[0025] Figure 3 It is a schematic structural diagram of another green laser provided by an embodiment of the present invention;

[0026] Figure 4 It is a schematic structural diagram of yet another green laser provided by an embodiment of the present invention;

[0027] Figure 5 It is a schematic structural diagram of yet another green laser provided by an embodiment of the present invention;

[0028] Figure 6 It is a schematic structural diagram of yet another green laser provided by an embodiment of the present invention;

[0029] Wherein, 10 - pump source, 20 - first reflector, 30 - laser crystal, 40 - polarization beam splitter, 50 - second reflector, 60 - frequency doubling crystal, 70 - telescope lens group, 71 - plano-convex lens, 72 - plano-concave lens, 73 - base, 80 - beam splitter, 90 - indicating light source, 100 - focusing lens, 110 - coupling optical fiber, 120 - fiber optic connector, 130 - light absorbing component. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0032] Compared with the short-pulse laser output by a nanosecond Q-switched laser and the ultrashort-pulse laser output by a picosecond or even femtosecond mode-locked laser, the millisecond-long pulsed green light achieved through power modulation has a relatively low peak power of the fundamental-frequency laser and poor output beam quality, resulting in difficulty in achieving a high beam quality output. To solve the above problems, an embodiment of the present invention provides a green light laser. Figure 1 It is a schematic structural diagram of a green light laser provided by an embodiment of the present invention. Refer to Figure 1, the green laser includes a pump source 10, a first mirror 20 arranged along a first optical axis x, a laser crystal 30, a polarization beam splitter 40, a second mirror 50 arranged along a second optical axis y, a frequency doubling crystal 60, a telescope lens group 70, and a beam splitter 80. The first optical axis x and the second optical axis y are parallel. The pump source 10 is arranged on one side of the laser crystal 30. The pump source 10 is used to provide pulsed pump light with a millisecond pulse width to the laser crystal 30. The laser crystal 30 is used to absorb the pulsed pump light and generate fundamental frequency laser in the infrared band. The fundamental frequency laser is transmitted in the resonant cavity formed by the first mirror 20 and the second mirror 50. The fundamental frequency laser reflected by the first mirror 20 or emitted by the laser crystal 30 is incident on the polarization beam splitter 40 and is split into a P-polarized light a and an S-polarized light b by the polarization beam splitter 40. The P-polarized light a is transmitted by the polarization beam splitter 40 and transmitted out of the resonant cavity. The S-polarized light b is reflected by the polarization beam splitter 40 at an angle of 45 degrees to the beam splitter 80, and after being reflected by the beam splitter 80, transmitted through the telescope lens group 70 and the frequency doubling crystal 60, it is incident on the second mirror 50. After being reflected by the second mirror 50, it is transmitted in the resonant cavity and then transmitted out through the beam splitter 80. Among them, the telescope lens group 70 is used to converge the fundamental frequency laser to the frequency doubling crystal 60 to generate frequency doubling laser in the green light band, and the frequency doubling laser is transmitted out through the beam splitter 80.

[0033] Among them, the pump source 10 is used to provide the energy required to generate the fundamental frequency laser. In this embodiment, the pump source 10 is arranged on one side of the laser crystal 30, and the fundamental frequency laser in the infrared band is generated by the method of side pumping. The laser crystal 30 can be a neodymium-doped yttrium aluminum garnet Nd:YAG crystal rod. The frequency doubling laser in the green light band can be green laser with a wavelength of 500 nm to 560 nm, and the fundamental frequency laser in the infrared band can be near-infrared laser with a wavelength of 1000 nm to 1120 nm. Specifically, in implementation, the wavelength of the fundamental frequency laser in the infrared band can be 1064 nm, 1030 nm, 1054 nm, and the wavelength of the frequency doubling laser in the green light band can be 532 nm, 515 nm, 527 nm. In the following embodiments, the wavelength of the fundamental frequency laser is 1064 nm and the wavelength of the frequency doubling laser is 532 nm for illustration, which is not a limitation to the present invention. Optionally, the pump source 10 includes a xenon lamp or an 808 nm semiconductor laser. Exemplarily, when the pump source 10 uses a xenon lamp, the Nd:YAG crystal rod and the xenon lamp can be assembled in a gold-plated cavity. The xenon lamp is a high-pressure gas discharge lamp, which is filled with a mixed gas of inert gas xenon and has a wide emission wavelength range, covering from ultraviolet to near-infrared, especially having an emission peak near 800 nm, which matches the main absorption peak of Nd ions. In addition, Nd 3+The ions also have other absorption peaks in the visible light range, which can fully absorb the pumping energy of the xenon lamp, thereby improving the efficiency. The xenon lamp is driven by an external power supply and can achieve millisecond (ms)-level pulse modulation to realize quasi-continuous laser output with a pulse width of ms. In other embodiments, the pump source 10 can also adopt a semiconductor laser of 808 nm, and specific implementation can be designed according to actual situations.

[0034] The first reflector 20 and the second reflector 50 are total reflection lenses, which form a laser resonator. Laser oscillates between the first reflector 20 and the second reflector 50 to generate infrared fundamental frequency laser in the 1064 nm band. Optionally, a total reflection film in the 1064 nm band (reflectivity R≥99.5%) is provided on the surface of the first reflector 20 close to the laser crystal 30, and the other surface is not coated. Total reflection films in the 1064 nm band and the 532 nm band (reflectivity R≥99.5%) are provided on the surfaces of the second reflector 50 close to the frequency doubling crystal 60, and the other surface is not coated to avoid light loss. The polarization beam splitter 40 can be a high-power polarization beam splitter (PBS) prism or a 45° polarization beam splitter; the beam splitter 80 can be a 45° dichroic mirror at an angle of 45° with the y optical axis, which is used to reflect the fundamental frequency laser and transmit the frequency doubled laser. Optionally, a total reflection film in the 1064 nm band (reflectivity R≥99.5%) and a high-transmission film in the 532 nm band (transmittance T≥99.5%) are provided on the surface of the beam splitter 80 close to the polarization beam splitter 40, and a high-transmission film in the 532 nm band is provided on the side far from the polarization beam splitter 40.

[0035] Among them, the tolerance power threshold range of the high-power polarization beam splitter (PBS) prism for millisecond-level pulsed laser is: tolerance power density <5 kW / cm 2 , single pulse energy density 1 J / cm 2 ~50 J / cm 2 .

[0036] The high-power PBS crystal (prism) / 45° polarization beam splitter can split the incident unpolarized light into two perpendicular linearly polarized lights. Among them, the P-polarized light a passes through completely, while the S-polarized light b is reflected at an angle of 45°, and the outgoing direction forms a 90° angle with the P-polarized light a, so that the fundamental frequency laser after passing through the high-power PBS crystal / 45° polarization beam splitter becomes polarized light; of course, the specific reflection angle and outgoing direction angle can be specifically determined according to design requirements. A 1064 nm polarization beam splitting dielectric film is coated on the middle inclined surface of the high-power PBS prism, and an antireflection film of 1064 nm is coated on other right-angle surfaces. In the process of generating green light by frequency doubling, the use of polarization-maintaining light (i.e., laser with a stable polarization state, which is S-polarized light in this embodiment) mainly has the following reasons:

[0037] 1. Meet the phase matching condition

[0038] The frequency doubling process needs to satisfy the phase matching condition, that is, the polarization states of the fundamental frequency light and the frequency-doubled light need to be precisely matched. For example, type-I phase matching requires the fundamental frequency laser to be linearly polarized light (such as ordinary light, i.e., o-light), and the frequency-doubled laser to be another polarization state (such as extraordinary light, i.e., e-light). If a non-polarized or randomly polarized light source is used, it will cause polarization state fluctuations and cannot effectively satisfy the phase matching condition, thus significantly reducing the frequency doubling efficiency.

[0039] 2. Improve the conversion efficiency

[0040] Polarization-maintaining light can ensure the stability of the polarization state of the laser and reduce the energy loss caused by polarization changes. The frequency doubling effect in the nonlinear crystal is phase-sensitive, and a stable polarization state helps to maintain the coherent superposition of the frequency-doubled laser and the fundamental frequency laser, thereby improving the energy conversion efficiency.

[0041] 3. Enhance the output stability

[0042] In applications such as laser display and laser imaging, the stability and power density of the green light output are crucial. Polarization-maintaining light can reduce the green light power fluctuations caused by polarization state fluctuations and ensure the output quality.

[0043] The frequency doubling crystal 60 can be a potassium titanyl phosphate (KTiOPO4) KTP crystal. The KTP crystal is an excellent nonlinear (NLO) crystal with a large nonlinear coefficient, a wide acceptance angle, and a walk-off angle, and is widely used for doubling the frequency of Nd 3+ infrared lasers to generate green lasers. The lithium triborate (LiB3O5) LBO crystal can also be selected. In specific implementation, it can be selected according to the actual situation.

[0044] The telescope lens group 70 consists of two lenses, including a plano-convex lens and a plano-concave lens, which are used to optimize the beam quality of the fundamental frequency laser, improve the power density of the fundamental frequency laser on the frequency doubling crystal 60, and improve the frequency doubling efficiency. Figure 2 It is a schematic structural diagram of a telescope lens group provided by an embodiment of the present invention. Refer to Figure 2 , optionally, the telescope lens group includes a plano-convex lens 71 and a plano-concave lens 72. Optionally, the telescope lens group further includes a base 73 and a six-axis adjustment bracket ( Figure 2 not shown), and the plano-convex lens 71 and the plano-concave lens 72 are fixed to the base 73 through the six-axis adjustment bracket.

[0045] Among them, the base 73 can be a metal base. The plano-convex lens 71 and the plano-concave lens 72 are bonded to the metal base through a six-axis adjustment bracket. The six-axis adjustment bracket can adjust six degrees of freedom including up and down, front and back, and pitch of the lens to ensure that the plano-convex lens 71 and the plano-concave lens 72 are coaxial. The middle part of the metal base is hollow, and the laser can pass through without obstruction. The telescope lens group can compress the beam quality of the fundamental frequency laser, thereby compressing the spot size of the laser incident on the laser crystal in the laser cavity, and improving the energy density of the fundamental frequency laser on the frequency doubling crystal, so as to improve the frequency doubling efficiency of the laser from infrared laser to green laser to a certain extent.

[0046] The technical solution of the embodiment of the present invention optimizes the design of the entire optical system, introduces a telescope lens group to optimize the beam quality of the fundamental frequency laser, improves the power density of the fundamental frequency laser on the frequency doubling crystal, and improves the overall frequency doubling efficiency. The polarized fundamental frequency laser is used to meet the phase matching condition of frequency doubling, improve the conversion efficiency, and enhance the output stability of the frequency doubling laser. Without damaging the frequency doubling crystal, the overall optical-optical conversion efficiency is improved. Its maximum single pulse energy can reach 5J at most, the maximum peak power is 2kW, and the pulse width is between 0.05ms and 5ms. It effectively solves the problem of low absorption of 1μm band laser by high-reflectivity materials and can be applied to laser welding machines for high-reflectivity materials such as copper and aluminum.

[0047] Figure 3 It is a schematic structural diagram of another green laser provided by the embodiment of the present invention. Refer to Figure 3 , Optionally, the green laser further includes an indicating light source 90. The indicating light source 90 is located on the side of the first mirror 20 away from the laser crystal 30. The indicating light source 90 is used to emit indicating light in the visible light band, and the indicating light source is used for the optical path debugging of the green laser.

[0048] It can be understood that since the fundamental frequency laser is infrared light in the 1064nm band and its light is invisible, setting the indicating light in the visible light band can be used for optical path debugging. Specifically, in implementation, the indicating light can be selected as red light, and the indicating light source 90 can be a helium-neon laser. The 632.8nm red light emitted by the helium-neon laser is visible light and has no influence on the frequency doubling crystal. In other embodiments, other light sources with other wavelengths can also be selected, and the embodiment of the present invention does not limit this. On the other hand, since the laser energy is relatively high, to avoid hurting the human eye, the indicating light can show the transmission direction of the fundamental frequency laser, avoiding direct viewing of the laser by the staff and improving safety.

[0049] Figure 4 It is a schematic structural diagram of yet another green laser provided by the embodiment of the present invention. Refer to Figure 4, Optionally, the green laser further includes a focusing lens 100 and a coupling optical fiber 110 located on the light output side of the beam splitter 80. The frequency-doubled laser is focused by the focusing lens 100 and then coupled into the coupling optical fiber 110.

[0050] Among them, the focusing lens 100 may include at least one convex lens, and the specific structure can be designed according to the actual situation. In specific implementation, antireflection films with a wavelength of 532 nm (T≥99.5%) can be provided on the two surfaces of the focusing lens 100. The coupling optical fiber 110 can be a multimode optical fiber, and the coupling optical fiber 110 can achieve flexible laser transmission to meet the application requirements of laser welding.

[0051] Continue to refer to Figure 4 , Optionally, an optical fiber connector 120 is provided on the side of the coupling optical fiber 110 close to the focusing lens 100. The optical fiber connector 120 can be a D80 optical fiber connector. The setting of the optical fiber connector 120 can improve the coupling efficiency of the laser into the coupling optical fiber 110. Antireflection films with a wavelength of 532 nm can also be provided on the end face of the optical fiber connector 120 to improve the coupling efficiency.

[0052] Figure 5 Schematic diagram of the structure of another green laser provided by an embodiment of the present invention. Refer to Figure 5 , Optionally, the green laser further includes an absorbing component 130 provided on the side of the polarization beam splitter 40 away from the laser crystal 30. The absorbing component 130 is used to absorb P-polarized light.

[0053] Since the P-polarized light output outside the resonant cavity is not utilized, the setting of the absorbing component 130 to absorb the P-polarized light can avoid irradiating the human eye and improve safety.

[0054] It can be understood that the various parts in the above embodiments can be combined with each other to form more embodiments. Exemplarily, Figure 6 Schematic diagram of the structure of another green laser provided by an embodiment of the present invention. Refer to Figure 6 , The green laser includes a pump source 10, a first mirror 20, a laser crystal 30, a polarization beam splitter 40, a second mirror 50, a frequency doubling crystal 60, a telescope lens group 70, a beam splitter 80, an indicating light source 90, a focusing lens 100, a coupling optical fiber 110, and an optical fiber connector 120. The pump source 10 provides pump light in the millisecond level, and finally outputs green light with a maximum single pulse energy of up to 5 J, a maximum peak power of 2 kW, and a pulse width in the range of 0.05 ms to 5 ms.

[0055] An embodiment of the present invention also provides a laser welding machine, which includes any one of the green lasers provided in the above embodiments. The laser welding machine can be used for welding materials such as copper and aluminum.

[0056] The laser welding machine provided by the embodiment of the present invention includes any one of the green light lasers provided by the above embodiments, and has the same or corresponding technical effects as the green light laser, which will not be elaborated here.

[0057] The above specific implementation manners do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A green laser, characterized in that, The invention comprises a pump source, a first reflector arranged along a first optical axis, a laser crystal and a polarization beam splitter, and a second reflector arranged along a second optical axis, a frequency doubling crystal, a telescope lens group and a beam splitter, wherein the first optical axis and the second optical axis are parallel; The pump source is arranged on one side of the laser crystal, and is used to provide pulsed pump light to the laser crystal; The laser crystal is used to absorb the pulsed pump light and generate a fundamental frequency laser in the infrared band. The fundamental frequency laser is transmitted in the resonant cavity formed by the first reflector and the second reflector. The fundamental frequency laser reflected by the first reflector or emitted by the laser crystal is incident on the polarization beam splitter, and is split into P-polarized light and S-polarized light by the polarization beam splitter. The P-polarized light is transmitted by the polarization beam splitter and transmitted out of the resonant cavity. The S-polarized light is reflected by the polarization beam splitter to the beam splitter, reflected by the beam splitter, transmitted by the telescope lens group and the frequency-doubling crystal, and then incident on the second reflector. After being reflected by the second reflector, it is transmitted in the resonant cavity and transmitted through the beam splitter before being output. The telescope lens group is used to converge the fundamental frequency laser onto the frequency-doubling crystal to generate a frequency-doubling laser in the green light band, and the frequency-doubling laser is output after being transmitted through the spectroscope.

2. The green laser according to claim 1, characterized in that, The telescope lens group includes a plano-convex lens and a plano-concave lens.

3. The green laser according to claim 2, wherein The telescope lens assembly further comprises a base and a six-axis adjustment frame, and the plano-convex lens and the plano-concave lens are fixed on the base via the six-axis adjustment frame.

4. The green laser according to claim 1, characterized in that, It also includes an indicator light source, which is located on the side of the first reflector away from the laser crystal. The indicator light source is used to emit indicator light in the visible light band and is used for optical path debugging of the green laser.

5. The green laser according to claim 1, characterized in that, It also includes a focusing lens and a coupling optical fiber located on the light-emitting side of the beam splitter. The frequency-doubled laser is focused by the focusing lens and then coupled into the coupling optical fiber.

6. The green laser according to claim 5, characterized in that, The coupling optical fiber is provided with an optical fiber connector on a side close to the focusing lens.

7. The green laser according to claim 1, wherein It also includes a light absorbing component arranged on a side of the polarization beam splitter away from the laser crystal, and the light absorbing component is used to absorb the P-polarized light.

8. The green laser according to claim 1, characterized in that, The surface of the first reflector close to the laser crystal is provided with a total reflection film for the infrared band, the surface of the second reflector close to the frequency doubling crystal is provided with a total reflection film for the infrared band and a total reflection film for the green light band, the surface of the beam splitter close to the polarization beam splitter is provided with a total reflection film for the infrared band and a high-transmittance film for the green light band, and the side away from the polarization beam splitter is provided with a high-transmittance film for the green light band.

9. The green laser according to claim 1, characterized in that, The polarization beam splitter includes a high-power polarization beam splitter prism or a polarization beam splitter plate. The middle oblique surface of the high-power polarization beam splitter prism is provided with a polarization beam splitter film of the infrared band, and the right-angle surface of the polarization beam splitter prism is provided with an anti-reflection film of the infrared band.

10. A laser welding machine, characterized in that, The green laser comprises the green laser according to any one of claims 1 to 9.

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