High-energy fiber-coupled laser for impact strengthening

Abstract

The application relates to the field of laser technology, in particular to a high-energy fiber-coupled laser for impact strengthening, which comprises a Cassegrain unstable resonant cavity, a Cassegrain unstable resonant cavity mirror, a plano-convex total reflection mirror and a Gauss output mirror, a laser pulse modulation assembly, a first laser gain assembly and a polarizing assembly arranged between the plano-convex total reflection mirror and the Gauss output mirror, a frequency doubling assembly comprising a beam-reducing system and a frequency doubling crystal, a second laser gain assembly arranged between the frequency doubling assembly and the Cassegrain unstable resonant cavity, a fiber-coupled assembly with a homogenizer, an attenuator and a beam-expanding system, a honeycomb mirror arranged behind the beam-expanding system, a focusing mirror arranged behind the honeycomb mirror and an optical fiber arranged behind the focusing mirror. The application can improve the problem that high-intensity laser pulses cause damage to the entrance surface of the optical fiber and the internal core material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser technology, in particular to a large energy fiber coupling laser for impact strengthening. BACKGROUND

[0002] In the production practice application, metal materials often produce defects due to fatigue, corrosion and wear and other factors, and serious defects can greatly reduce the service life of the parts and even cause the operation failure of the facilities, causing huge economic losses.

[0003] A fiber laser coupler is disclosed in Chinese Patent No. CN110320593A, which comprises a laser input cable, a laser shaping coupling device and a multi-beam mode energy transmission fiber. The multi-beam mode energy transmission fiber comprises a circular core and a ring core, each ring core is coaxial with the circular core. A fluorine-doped layer is arranged between the circular core and the ring core, and a fluorine-doped layer is also arranged between adjacent ring cores. The adjustable collimating lens group and the adjustable focusing lens group of the laser shaping coupling device can move horizontally along the direction of the laser beam in the shell of the laser shaping coupling device. The laser shaping coupling device is used to couple the laser beam input by the laser input cable into different cores in the multi-beam mode energy transmission fiber to obtain output laser beams of different beam modes. However, in actual use, the fiber laser coupler has the problem of damage to the entrance surface of the fiber and the internal core material of the laser pulse. SUMMARY

[0004] To this end, the present application provides a large energy fiber coupling laser for impact strengthening to solve the problem of damage to the entrance surface of the fiber and the internal core material of the laser pulse in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides a large energy fiber coupling laser for impact strengthening, which comprises a Cassegrain unstable resonant cavity, a Cassegrain unstable resonant cavity mirror, a plano-convex total reflection mirror and a Gaussian output mirror, a laser pulse modulation assembly, a first laser gain assembly and a polarizing assembly between the plano-convex total reflection mirror and the Gaussian output mirror.

[0006] A frequency doubling assembly comprising a beam-reducing system and a frequency doubling crystal, a second laser gain assembly between the frequency doubling assembly and the Cassegrain unstable resonant cavity.

[0007] A fiber coupling assembly with a homogenizer, comprising an attenuator and a beam-expanding system, a honeycomb mirror behind the beam-expanding system, and a focusing mirror behind the honeycomb mirror.

[0008] A fiber, which is arranged behind the focusing mirror.

[0009] Further, the plano-convex total reflection mirror comprises a first convex surface, and the Gauss output mirror comprises a second convex surface, and the first convex surface is oppositely arranged with the second convex surface.

[0010] Further, the laser pulse modulation assembly comprises a 1 / 4 wave plate, an electro-optical Q switch and a first polarizer, the convex direction of the first convex surface is the laser emission direction, and the 1 / 4 wave plate, the electro-optical Q switch and the first polarizer are sequentially arranged along the laser emission direction.

[0011] Further, the first laser gain assembly comprises a first side-pumped gain module, a second side-pumped gain module and a first optical rotatory crystal, and the first side-pumped gain module, the first optical rotatory crystal and the second side-pumped gain module are sequentially arranged behind the first polarizer along the laser emission direction.

[0012] Further, the polarizing assembly comprises a first half wave plate and a second polarizer, and the first half wave plate and the second polarizer are sequentially arranged behind the second side-pumped gain module along the laser emission direction, and the second polarizer is hinged in the Cassegrain non-stable resonant cavity.

[0013] Further, a reflective beam expansion assembly is further arranged between the second laser gain assembly and the Cassegrain non-stable resonant cavity, and the reflective beam expansion assembly comprises oppositely arranged first and second reflecting mirrors, and the first and second reflecting mirrors are sequentially arranged with a first plano-concave lens and a first plano-convex lens therebetween.

[0014] Further, the second laser gain assembly comprises a first side-pumped rod crystal module and a second side-pumped rod crystal module, and a second optical rotatory crystal is arranged between the first side-pumped rod crystal module and the second side-pumped rod crystal module.

[0015] Further, the beam expansion system comprises a second plano-convex lens and a second plano-concave lens sequentially arranged along the laser emission direction, and the beam expansion system and the second laser gain assembly define third and fourth reflecting mirrors oppositely arranged along the laser emission direction.

[0016] Further, the attenuator comprises a second half wave plate and a third polarizer, and the attenuator and the frequency doubling crystal mirror oppositely arrange first and second beam splitters along the laser emission direction, the second half wave plate is arranged behind the second beam splitter, and the third polarizer is hinged behind the second half wave plate.

[0017] Further, the fiber coupling assembly with homogenizer only comprises one piece of honeycomb mirror, and the beam expansion system comprises a third plano-concave lens and a third plano-convex lens, and the third convex surface of the third plano-convex lens faces the plane of the third plano-concave lens.

[0018] Compared with the prior art, the beneficial effects of the present application are that the seed light with approximately flat-top distribution of laser light intensity is output by the Cassegrain unstable resonant cavity, and the light intensity after subsequent amplification and frequency doubling is more uniform than the resonant cavity form of the prior art; and before coupling, the laser is expanded and then split into several beams by the honeycomb mirror to average the spatial distribution of laser power density, and then the sub-beams are superimposed and output by the focusing mirror to realize the homogenization of the light beam, and then coupled into the optical fiber to relieve the damage to the entrance surface and core material inside of the optical fiber caused by high-intensity laser pulses. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structure schematic view of the high-energy fiber coupling laser for impact strengthening of the present embodiment.

[0020] Figure 2 It is a comparison graph of flat-top distribution and Gaussian distribution intensity. DETAILED DESCRIPTION

[0021] In order to make the purpose and advantages of the present application more clear and understandable, the present application will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0022] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and are not used to limit the protection scope of the present application.

[0023] It should be noted that in the description of the present application, the terms indicating the direction or positional relationship of "up", "down", "left", "right", "inner", "outer" and the like are based on the direction or positional relationship shown in the drawings, which is only for the convenience of description, and is not indicative or suggestive of the device or element having a specific orientation, being constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0024] In addition, it should also be noted that in the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. Those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0025] Please refer to Figure 1 The structure schematic view of the high-energy fiber coupling laser for impact strengthening of the present embodiment is shown in the figure, and the high-energy fiber coupling laser for impact strengthening comprises:

[0026] The Cassegrain unstable resonant cavity 1 comprises a Cassegrain unstable resonant cavity mirror, which comprises a plano-convex total reflection mirror 101 and a Gaussian output mirror 102, and a laser pulse modulation assembly 103, a first laser gain assembly 104 and a polarizing assembly 105 are arranged between the plano-convex total reflection mirror 101 and the Gaussian output mirror 102.

[0027] The frequency doubling assembly 2 comprises a beam-reducing system 201 and a frequency doubling crystal 202, and a second laser gain assembly 7 is arranged between the frequency doubling assembly 201 and the Cassegrain unstable resonant cavity 1.

[0028] The fiber coupling assembly 3 with a homogenizer comprises an attenuator 301 and a beam-expanding system 302, and a honeycomb mirror 4 is arranged behind the beam-expanding system 301, and a focusing mirror 5 is further arranged behind the honeycomb mirror 4.

[0029] The fiber 6 is arranged behind the focusing mirror 5.

[0030] Specifically, the device is applied to laser strengthening of materials underwater, and the impact strengthening high-energy fiber coupling laser outputs seed light with approximately flat-top distribution of laser light intensity through the Cassegrain unstable resonant cavity 1, and the light intensity is more uniform after subsequent amplification and frequency doubling compared with the resonant cavity form of the prior art; and before coupling, the laser is expanded first, and then the honeycomb mirror 4 is used to divide the laser into several beams, average the spatial distribution of laser power density, and then the sub-beams are superimposed and output through the focusing mirror 5, so as to realize homogenization of the beams, and then the beams are coupled into the fiber, so as to relieve damage to the entrance surface of the fiber and the internal core material of the fiber caused by high-intensity laser pulses.

[0031] Specifically, in the embodiment, the cavity length L of the Cassegrain unstable resonant cavity 1 is 600 mm.

[0032] Specifically, the plano-convex total reflection mirror 101 comprises a first convex surface 1011, and the Gaussian output mirror 102 comprises a second convex surface 1021, and the first convex surface 1011 and the second convex surface 1021 are arranged oppositely.

[0033] Specifically, the curvature R1 of the plano-convex total reflection mirror 101 is 6 m; the 2a of the Gaussian output mirror 102 is 6, the 2b is 0, the curvature R2 is 1.5 m, and the transmittance T is 70%.

[0034] Specifically, the laser pulse modulation assembly 103 comprises a 1 / 4 wave plate 1031, an electro-optic Q switch 1032 and a first polarizer 1033, the convex direction of the first convex surface 1011 is the laser emission direction, and the 1 / 4 wave plate 1031, the electro-optic Q switch 1032 and the first polarizer 1033 are sequentially arranged along the laser emission direction.

[0035] Specifically, before the laser oscillation is formed, the transmitted light emitted by the first laser gain assembly 104 passes through the first polarizer 1033, the electro-optical Q-switch 1032 and the 1 / 4 wave plate 1031 in sequence. The 1 / 4 wave plate 1031, the electro-optical Q-switch 1032 and the first polarizer 1033 arranged in sequence can modulate the pulsed laser, thereby realizing nanosecond laser output.

[0036] Specifically, the modulation of the pulsed laser refers to that when the laser upper level inversion particle number accumulates to a preset level, the electro-optical Q-switch 1032 is applied with 1 / 4 wave voltage by the high-voltage driving power supply, the longitudinal electro-optic effect is used to make the laser oscillator for releasing laser in an open door working state, and nanosecond laser output is realized.

[0037] Specifically, the first laser gain assembly 104 includes a first side-pumped gain module 1041, a second side-pumped gain module 1043 and a first optical rotatory crystal 1042, and the first side-pumped gain module 1041, the first optical rotatory crystal 1042 and the second side-pumped gain module 1043 are arranged in sequence behind the first polarizer 1033 along the laser emission direction.

[0038] Specifically, the first side-pumped gain module 1041 and the second side-pumped gain module 1043 are both Nd:YAG crystal rods with a diameter of 7 mm, a length of 94 mm and a doping concentration of 0.8% at, and the first optical rotatory crystal 1042 can compensate the thermal-induced birefringence in the crystal; and the plane-convex total reflection mirror 101 and the Gauss output mirror 102 cooperate to generate pulsed laser.

[0039] Specifically, the polarizing assembly 105 includes a first half wave plate 1051 and a second polarizer 1052, and the first half wave plate 1051 and the second polarizer 1052 are arranged in sequence behind the second side-pumped gain module 1043 along the laser emission direction, and the second polarizer 1052 is hinged in the Cassegrain non-stable resonant cavity 1.

[0040] Specifically, the first half wave plate 1051 and the second polarizer 1052 are arranged to select and polarize, and high-energy output and high-polarization-ratio laser can be obtained.

[0041] Specifically, the second laser gain assembly 7 and the Cassegrain non-stable resonant cavity further have a reflective beam expanding assembly 8 therebetween, the reflective beam expanding assembly 8 includes oppositely arranged first and second reflective mirrors 801 and 802, and the first and second reflective mirrors 801 and 802 further have a first plane-concave lens 803 and a first plane-convex lens 804 arranged in sequence therebetween.

[0042] Specifically, the direction of the laser is changed by the first mirror 801 and the second mirror 802, both of which are 45° mirrors, and the laser is guided into the second laser gain assembly 7, wherein the combination of the first plano-concave lens 803 and the first plano-convex lens 804 can shape the light beam when the laser passes through the two lenses in turn, and by adjusting the parameters and relative positions of the two lenses, a light beam output with specific shape and characteristics can be obtained.

[0043] Specifically, the second laser gain assembly 8 comprises a first side-pumped rod crystal module 701 and a second side-pumped rod crystal module 703, and a second optical rotatory crystal 702 is arranged between the first side-pumped rod crystal module 701 and the second side-pumped rod crystal module 703.

[0044] Specifically, the first side-pumped rod crystal module 701 and the second side-pumped rod crystal module 703 are both Nd:YAG crystal rods with a diameter of 8 mm, a length of 140 mm, a doping concentration of 0.8% at, and an end face angle of 2°, which can avoid the return of the back light to damage the previous optical path device, and the second optical rotatory crystal 702 is similar to the seed light, which can reduce the depolarization influence caused by thermal-induced birefringence and improve the polarization degree of the amplified laser.

[0045] Specifically, the beam-reducing system 201 comprises a second plano-convex lens 2012 and a second plano-concave lens 2011 arranged in sequence along the laser emission direction, and the beam-reducing system 201 and the second laser gain assembly 7 define a third mirror 9 and a fourth mirror 10 arranged opposite to each other along the laser emission direction.

[0046] Specifically, the third mirror 9 and the fourth mirror 10 are both 45° mirrors, and the third mirror 9 and the fourth mirror 10 can adjust the direction of the laser and guide the laser into the beam-reducing system so as to reduce the laser by the second plano-convex lens 2012 and the second plano-concave lens 2011.

[0047] Specifically, the attenuator 301 comprises a second half-wave plate 3011 and a third polarizer 3012, and the attenuator 301 and the frequency-doubling crystal mirror 202 are arranged opposite to each other along the laser emission direction and define a first beam splitter 11 and a second beam splitter 12, the second half-wave plate 3011 is arranged behind the second beam splitter 12, and the third polarizer 3012 is hinged behind the second half-wave plate 3011.

[0048] Specifically, when the laser passes through the frequency doubling crystal 202, the fundamental light in the laser is filtered out through the first beam splitter 11 and the second beam splitter 12, wherein the frequency doubling crystal 202 is an LBO crystal mirror, the LBO crystal mirror is a lithium triborate crystal, the size is 6*6*20cm, θ=90°, φ=9.6°, the front and rear end faces are coated with 532nm&1064nm antireflection film, and temperature phase matching is adopted, a temperature controller is used to control the temperature, and the temperature control accuracy is ±0.1℃.

[0049] Specifically, the fiber coupling assembly 3 with the homogenizer only contains a piece of honeycomb mirror 4, the beam expanding system 302 includes a third plano-concave lens 3021 and a third plano-convex lens 3022, and the third convex surface 3023 of the third plano-convex lens 3022 faces the plane 3024 of the third plano-concave lens 3021.

[0050] Specifically, the third plano-concave lens 3021 and the third plano-convex lens 3022 can expand the laser beam.

[0051] Specifically, when the laser passes through the third plano-concave lens 3021 and the third plano-convex lens 3022 and is expanded, it passes through the honeycomb mirror 4 to be divided into several beams, and then the sub-beams are superimposed and output through the focusing lens 5, so as to realize the homogenization of the beam, weaken the dispersed strong points, and alleviate the damage of high-intensity laser pulses to the entrance surface and core material of the optical fiber 6.

[0052] Please refer to Figure 2 The longitudinal coordinate is the relative intensity, and the transverse coordinate is the position. As can be seen from the figure, the relative intensity of the flat-top distribution is reduced by half compared with the Gaussian distribution.

[0053] Specifically, under the same conditions, the honeycomb mirror 4 homogenizes the light spot to increase the fiber coupling output power by one time, and avoids the air breakdown problem of the focused beam of the focusing lens 5.

[0054] Specifically, the parameters of the honeycomb mirror 4 are as follows: focal length f=100mm, pitch=1000um, and the sub-unit shape is hexagonal, ~ SINα=0.005; and the parameters of the focusing lens 5 are as follows: focal length f=50mm, and coated with 532nm antireflection film.

[0055] Specifically, the pitch refers to the distance between the centers of two adjacent sub-units. ~ SINα refers to the approximation of the sine value of the angle related to the focusing characteristic.

[0056] The technical scheme of the present application has been described in combination with the preferred embodiments shown in the drawings, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical schemes after the changes or replacements will all fall within the protection scope of the present application.

Claims

1. A high-energy fiber-coupled laser for impact strengthening, characterized by, The application relates to a laser device. The Cassegrain unstable resonant cavity comprises a Cassegrain unstable resonant cavity mirror, a laser pulse modulation component, a first laser gain component and a polarizing component are arranged between a plano-convex total reflection mirror and a Gauss output mirror, The plano-convex total reflection mirror comprises a first convex surface, the Gauss output mirror comprises a second convex surface, the first convex surface is arranged opposite to the second convex surface, and the convex direction of the first convex surface is the laser emission direction, The laser pulse modulation component comprises a 1 / 4 wave plate, an electro-optical Q switch and a first polarizer, and the 1 / 4 wave plate, the electro-optical Q switch and the first polarizer are sequentially arranged along the laser emission direction, The first laser gain component comprises a first side-pumped gain module, a second side-pumped gain module and a first optical rotatory crystal, and the first side-pumped gain module, the first optical rotatory crystal and the second side-pumped gain module are sequentially arranged behind the first polarizer along the laser emission direction; A frequency doubling component comprises a beam shrinking system and a frequency doubling crystal, and a second laser gain component is arranged between the frequency doubling component and the Cassegrain unstable resonant cavity; A fiber coupling component with a homogenizer comprises an attenuator and a beam expanding system, a honeycomb mirror is arranged behind the beam expanding system, and a focusing mirror is further arranged behind the honeycomb mirror; An optical fiber is arranged behind the focusing mirror.

2. The high-energy fiber-coupled laser for impact strengthening according to claim 1, characterized by, The polarizing component comprises a first half wave plate and a second polarizer, the first half wave plate and the second polarizer are sequentially arranged behind the second side-pumped gain module along the laser emission direction, and the second polarizer is hinged in the Cassegrain unstable resonant cavity.

3. The high-energy fiber-coupled laser for impact strengthening according to claim 1, characterized by, A reflective beam expanding component is further arranged between the second laser gain component and the Cassegrain unstable resonant cavity, the reflective beam expanding component comprises oppositely arranged first and second reflectors, and a first plano-concave lens and a first plano-convex lens are sequentially arranged between the first and second reflectors.

4. The high-energy fiber-coupled laser for impact strengthening according to claim 3, characterized by, The second laser gain component comprises a first side-pumped rod crystal module and a second side-pumped rod crystal module, and a second optical rotatory crystal is arranged between the first and second side-pumped rod crystal modules.

5. The high-energy fiber-coupled laser for impact strengthening according to claim 4, characterized by, The beam shrinking system comprises a second plano-convex lens and a second plano-concave lens which are sequentially arranged along the laser emission direction, and a third reflector and a fourth reflector are oppositely arranged along the laser emission direction between the beam shrinking system and the second laser gain component.

6. The high-energy fiber-coupled laser for impact strengthening according to claim 5, characterized by, The attenuator comprises a second half wave plate and a third polarizer, first and second light splitting mirrors are oppositely arranged along the laser emission direction between the attenuator and the frequency doubling crystal, the second half wave plate is arranged behind the second light splitting mirror, and the third polarizer is hinged behind the second half wave plate.

7. The high-energy fiber-coupled laser for impact strengthening according to claim 1, characterized by, The fiber coupling component with the homogenizer only comprises one honeycomb mirror, the beam expanding system comprises a third plano-concave lens and a third plano-convex lens, and the third convex surface of the third plano-convex lens faces the plane of the third plano-concave lens.

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