A picosecond laser with high beam quality

Abstract

The application relates to a picosecond laser with high beam quality, comprising: a pump source for providing pump energy to an amplification crystal; a laser oscillator for providing high-beam-quality signal light to the amplification crystal; the amplification crystal for realizing amplification of signal light power; a pump light shaping system, which comprises a first lens group formed by a first plano-convex lens and a second plano-convex lens and a third plano-convex lens arranged at intervals with the first lens group, the pump light is subjected to quasi-collimation processing through the first lens group, and then is focused through the third plano-convex lens arranged at intervals, so that the Rayleigh length of the focused pump light completely falls in the amplification crystal; and a signal light shaping system, which comprises a fourth plano-convex lens arranged on the upstream of the light path of the amplification crystal and a second lens group formed by a fifth plano-convex lens and a first plano-concave lens, the signal light is focused through the fourth plano-convex lens, and then is subjected to expansion collimation through the second lens group, so that the Rayleigh length of the signal light completely falls in the amplification crystal, the pump light and the signal light are in a uniformly distributed state in the amplification crystal, the amplification crystal generates uniform heat distribution, the thermal lens effect is eliminated, the occurrence probability of the thermal birefringence effect and the thermal distortion effect is reduced, and the amplification efficiency of the light beam and the quality of the output light beam are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of picosecond lasers, in particular to a picosecond laser with high beam quality. BACKGROUND

[0002] The conventional high-energy single-pulse laser faces the problem of limited amplification power when its energy exceeds 1mJ and is in the order of ten picoseconds, and is accompanied by serious high-order mode effect, resulting in poor beam quality.

[0003] For high-energy diode-pumped solid-state lasers, under high-power pumping conditions, the laser crystal will produce significant thermal effects. Part of the pump light is effectively converted into laser output, while another part of the pump light is converted into heat and deposited inside the laser crystal. This heat deposition will cause uneven temperature distribution inside the crystal, which will further cause refractive index gradient distribution. This gradient distribution will further produce a series of thermal effects, including thermal lens effect, thermal-induced birefringence effect and thermal-induced distortion effect, etc.

[0004] It is worth noting that the thermal lens focal length of the laser crystal will change with the change of the pump power, which will further cause the corresponding change of the equivalent resonator and the fundamental mode volume. These changes will have an adverse effect on the further improvement of the beam quality and power of the output laser.

[0005] As an important parameter of laser, the beam quality determines the overall performance of the laser to a large extent. In many laser applications, the laser beam quality is often more critical than the laser power. For a laser with a certain output power, the better the beam quality, the higher the laser brightness. High beam quality can bring higher laser brightness, thereby improving the nonlinear conversion efficiency.

[0006] In laser cutting, drilling and other laser processing applications, high-quality laser beams can form smaller converging spots, which means that less laser power is needed to process the same material, and less material is wasted. At the same time, under the condition of the same converging spot size, the laser with high beam quality has smaller divergence angle and greater processing depth.

[0007] In military applications, high-quality laser beams are also of great significance. They can form smaller far-field spots, thereby enhancing the effect of laser. Therefore, controlling and improving the beam quality of laser is a key technical problem in the field. SUMMARY

[0008] Therefore, in view of the above problems, the present application provides a picosecond laser with high beam quality, which greatly improves the quality of the output beam of the laser.

[0009] To achieve the above object, the application provides a picosecond laser with high beam quality, comprising: a pump source for providing pump energy to an amplification crystal; a laser oscillator for providing high-beam-quality signal light to the amplification crystal; the amplification crystal for realizing amplification of signal light power; a pump light shaping system comprising a first lens group formed by a first plano-convex lens and a second plano-convex lens arranged between the pump source and the amplification crystal, and a third plano-convex lens arranged at intervals with the first lens group, wherein the pump light is subjected to quasi-collimation processing through the first lens group, and then focused through the third plano-convex lens arranged at intervals, so that the Rayleigh length of the focused pump light completely falls within the amplification crystal; and a signal light shaping system comprising a fourth plano-convex lens arranged upstream of the light path of the amplification crystal and a second lens group formed by a fifth plano-convex lens and a first plano-concave lens, wherein the signal light is focused through the fourth plano-convex lens, and then expanded and collimated through the second lens group, so that the Rayleigh length of the signal light completely falls within the amplification crystal.

[0010] In one of the specific embodiments, the diameter of the collimated light spot output by the lens group in the pump light shaping system is 1-1.5 mm, the third plano-convex lens arranged at intervals is located at a position with a light spot diameter of 3 mm, and the second lens group in the beam shaping system is placed at a position with a light spot diameter of 1-1.3 mm.

[0011] In one of the specific embodiments, the signal light provided by the laser oscillator has a power of 1-10 mw, an M2 less than 1.1, a pulse width of 10-100 picoseconds, and a repetition frequency of 20-50 KHZ.

[0012] In one of the specific embodiments, the amplification crystal comprises at least three stages of amplification crystals connected in series in the light path, wherein each stage of amplification crystal is separately provided with a pump source, and the signal light shaping system is arranged before each stage of amplification crystal.

[0013] In one of the specific embodiments, the optical path between the stages of amplification crystals is more than 1 m.

[0014] In one of the specific embodiments, the output light shaping system further comprises an eighth plano-convex lens and a ninth plano-convex lens arranged in confocal along the light path, and an aperture at the real focal points of the eighth plano-convex lens and the ninth plano-convex lens, wherein the signal light is focused through the eighth plano-convex lens, then transmitted through the aperture, and then transmitted to the ninth plano-convex lens to output the light beam.

[0015] In one of the specific embodiments, the pump source is an LD pump source, and the output laser has a wavelength of 888 nm.

[0016] In one of the specific embodiments, the amplification crystal is Nd:YVO4, the length is L, the amplification crystal is treated by gradient doping, the first section has a doping concentration of 0%, the length is L / 6, the second section has a doping concentration of 0.1%-0.2%, the length is L / 6, the third section has a doping concentration of 0.3%-0.5%, the length is L / 3, the fourth section has a doping concentration of 0.6%-0.8%, the length is L / 3, the first section is close to the pump source, and the fourth section is far away from the pump source.

[0017] In one of the specific embodiments, the substance doped in the amplification crystal is one of Er3+, Yb3+, Nd3+, Tm3+ or Pr3+.

[0018] In one of the specific embodiments, the amplification crystal is arranged on a crystal holder, a TEC temperature control is arranged around the crystal holder, and a water channel is arranged on the heating surface of the TEC for heat dissipation.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The pump light shaping system makes the Rayleigh length of the focused pump light completely fall within the amplification crystal, and the signal light shaping system makes the Rayleigh length of the signal light also completely fall within the amplification crystal, so that the pump light and the signal light can realize efficient and uniform interaction within the amplification crystal, the pump light provides energy, the signal light is amplified, and more importantly, the pump light and the signal light are in a uniformly distributed state within the amplification crystal, so that the heat generated by the amplification crystal during the laser amplification process is also uniform, the uniform heat distribution eliminates the thermal lens effect, reduces the probability of occurrence of the thermal birefringence effect and the thermal distortion effect, and greatly improves the beam amplification efficiency and the quality of the output light beam. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the picosecond laser with high beam quality. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the scope of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0023] In addition, the terms "first", "second", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an ordered ranking of the indicated technical features. Thus, features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly and specifically limited.

[0024] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0026] As shown in Figure 1 The embodiment provides a picosecond laser with high beam quality, which comprises a pump source 10 for providing pump energy to an amplification crystal 20, wherein the pump energy is absorbed by the amplification crystal 20 to excite particles in the amplification crystal to a high energy level, thereby providing a basis for subsequent laser generation; and a laser oscillator 30 for providing signal light with high beam quality to the amplification crystal 20, wherein the power of the signal light is 1mw, and the M 2The pulse width is 10 picoseconds, the repetition frequency is 20 KHZ, the amplification crystal 20 is used to realize amplification of the signal light power, the pump light shaping system 40 comprises a first lens group formed by a first plano-convex lens 401 and a second plano-convex lens 402 and a third plano-convex lens 403 which is arranged in a spaced manner with the first lens group, the pump light is subjected to quasi-collimation processing by the first lens group and then focused by the third plano-convex lens 403 which is arranged in a spaced manner, so that the Rayleigh length of the focused pump light completely falls within the amplification crystal 20, and the uniform distribution of the pump light within the amplification crystal 20 can be ensured, the signal light shaping system 50 comprises a fourth plano-convex lens 501 arranged on the upstream of the amplification crystal light path and a second lens group formed by a fifth plano-convex lens 502 and a first plano-concave lens 503 which are arranged at a distance of 1-1.3 mm from the light spot, the signal light is focused by the fourth plano-convex lens 501 and then expanded and collimated by the second lens group, so that the Rayleigh length of the signal light completely falls within the amplification crystal 20, and the uniform distribution of the signal light within the amplification crystal 20 can be ensured. In the embodiment, the pump light shaping system 40 and the signal light shaping system 50 are arranged, the pump light and the signal light interact within the amplification crystal 20, the pump light provides energy, the signal light is amplified, and because the pump light and the signal light are uniformly distributed within the amplification crystal 20, the heat generated by the amplification crystal is also uniform, and the uniform heat distribution can greatly eliminate the thermal lens effect, thereby improving the amplification efficiency of the light beam and the quality of the output light beam.

[0027] In one specific embodiment, the diameter of the collimated light spot output by the first lens group in the pump light shaping system 40 is 1-1.5 mm, more specifically, the diameter of the collimated light spot is 1.3 mm, the third plano-convex lens 403 is located at a position with a light spot diameter of 3 mm, and the diameter of the pump light spot after the final shaping is 2 mm, and the Rayleigh length is 160 mm.

[0028] In one specific embodiment, the signal light provided by the laser oscillator 30 has a power of 1-10 mw, an M2 less than 1.1, a pulse width of 10-100 picoseconds, and a repetition frequency of 20-50 KHZ.

[0029] In one of the specific embodiments, the amplification crystal 20 includes at least three stages of amplification crystals connected in series in the optical path, and each stage of amplification crystal is separately provided with a pump source, and the signal light shaping system is arranged before each stage of amplification crystal. For example, the optical path downstream of the amplification crystal 20 is further connected with a second-stage signal light shaping system 51 and a second-stage amplification crystal 52. The second-stage signal light shaping system 51 includes a sixth plano-convex lens 511 arranged upstream of the second-stage amplification crystal, and a third lens group formed by a seventh plano-convex lens 512 and a second plano-concave lens 513 located at a spot of 1 mm. The signal light is focused by the sixth plano-convex lens 511, and then expanded and collimated by the third lens group, so that the Rayleigh length of the signal light falls completely inside the second-stage amplification crystal 52. The second-stage pump source 10' provides pump light to the second-stage amplification crystal 52. The second-stage pump light shaping system 40' is arranged between the second-stage pump source 10' and the second-stage amplification crystal 52, and has the same structure and working principle as the above-mentioned embodiments, which will not be described here. Further, the optical path downstream of the second-stage amplification crystal 52 is further connected with a third-stage signal light shaping system 53 and a third-stage amplification crystal 54. The third-stage pump source 10'' provides pump light to the third-stage amplification crystal 54. The third-stage pump light shaping system 40'' is arranged between the third-stage pump source 10'' and the third-stage amplification crystal 54. The third-stage signal light shaping system 53 and the third-stage pump light shaping system 40'' have the same structure and working principle as the above-mentioned embodiments, which will not be described here.

[0030] In one of the specific embodiments, the optical path between each stage of amplification crystal is spaced apart by more than 1 m, and the signal light is transmitted in the optical path. The high-order modes at the edge will be divergent and lost during the transmission process, so that the high-order modes at the edge of the amplified light spot can be eliminated, and the high-order modes at the edge are prevented from entering the next stage of amplification crystal to be amplified again, so that heat is generated to cause the beam quality to be poor. For example, the spacing optical path between each stage of amplification crystal is more than 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, 9 m, or 10 m.

[0031] In one of the specific embodiments, an output light shaping system 60 is further included, which includes an eighth plano-convex lens 601 and a ninth plano-convex lens 602 arranged in series in the optical path, and an aperture 603 at the real focal points of the two plano-convex lenses. The signal light is focused by the eighth plano-convex lens 601, then transmitted through the aperture 603 to the ninth plano-convex lens 602 to output the light beam. The aperture 603 is used to eliminate the high-order modes in the light beam, and the output light beam is transmitted through the real focal points to obtain better beam quality.

[0032] In one of the specific embodiments, the multi-stage pump source is an LD pump source, the output laser has a wavelength of 888 nm, the absorption coefficients of the multi-stage amplification crystal to the pump light in different polarization directions are equal, the absorption coefficient of the YVO4 crystal to the 888 nm pump light is small, a crystal with a longer length can be used, the heat can be diffused in a larger volume, the heat effect in the crystal is alleviated, and high beam quality and high power laser output can be realized.

[0033] In one of the specific embodiments, the amplification crystal is Nd:YVO4 with a length of L, the amplification crystal is subjected to gradient doping treatment, the first section has a doping concentration of 0% and a length of L / 6, the second section has a doping concentration of 0.1%-0.2% and a length of L / 6, the third section has a doping concentration of 0.3%-0.5% and a length of L / 3, and the fourth section has a doping concentration of 0.6%-0.8% and a length of L / 3. The first section is close to one end of the pump source, and the fourth section is away from the other end of the pump source. In the embodiment, the amplification crystal is subjected to gradient doping treatment, the doping concentration gradually increases from the end close to the pump source, and the doping concentration is higher away from the pump end. By gradually increasing the doping concentration, the absorption efficiency of the pump light in the crystal is kept relatively stable, the heat generated by each section of the crystal is uniformly ensured, the heat of the pump light and the signal light is more uniformly distributed along the axial direction of the amplification crystal, the thermal lens effect is eliminated, and the beam amplification efficiency and the quality of the output beam are improved. Exemplarily, the substance doped in the amplification crystal is one of Er3+, Yb3+, Nd3+, Tm3+ or Pr3+.

[0034] In one of the specific embodiments, the amplification crystal is arranged on a crystal holder, a TEC temperature control is arranged around the crystal holder, a water channel is arranged on the heating surface of the TEC to dissipate heat, the temperature control accuracy, temperature control effect and temperature control speed are greatly improved, the temperature control accuracy can reach 0.1 ℃, the temperature around the crystal holder can be kept consistent, with the increase of the pump power, the heat generated by the crystal will continue to increase, the TEC temperature control can quickly respond and quickly control the temperature, and the temperature can be feedback adjusted according to the real-time heat and the cavity environment, so that the crystal temperature control is more stable.

[0035] It should be noted that, for those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0036] The principles and implementations of the present application are described in the specific examples, and the above examples are only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in specific implementation and application range. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A picosecond laser with high beam quality, characterized in that: The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device.

2. The picosecond laser with high beam quality of claim 1, wherein: The power of the signal light provided by the laser oscillator is 1 mw-10 mw, M 2 Less than 1.1, pulse width is 10-100 picoseconds, and the repetition frequency is 20-50 KHZ.

3. The picosecond laser with high beam quality of claim 1, wherein: The application relates to a high-power laser device.

4. The picosecond laser with high beam quality of claim 3, wherein: The application relates to a high-power laser device.

5. The picosecond laser with high beam quality of claim 3, wherein: The application relates to a high-power laser device.

6. The picosecond laser with high beam quality of claim 1, wherein: The application relates to a high-power laser device.

7. The picosecond laser with high beam quality of claim 1, wherein: The application relates to a high-power laser device.

8. The picosecond laser with high beam quality of claim 7, wherein: The application relates to a high-power laser device.

9. The picosecond laser with high beam quality of claim 1, wherein: The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. The application relates to a high-power laser device. 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