Lateral pumping structure adopting staggered arrangement of LDs

Abstract

The invention discloses a side pumping structure adopting staggered arrangement of LDs, and belongs to the technical field of high-power all-solid-state lasers, the side pumping structure comprises a laser crystal rod, a pumping module and a cooling system, the pumping module is composed of a plurality of circles of LD bar strip arrays, the LD bar strip arrays tightly surround the outer side of the laser crystal rod, the LD bar strip arrays comprise a plurality of LD bar strips, and the LD bar strips are arranged on the outer side of the laser crystal rod. The cooling system is integrated outside the pumping module, a quartz tube is sleeved on the outer side of the laser crystal rod, a high-reflection film is arranged on the outer wall of the quartz tube, and cooling water is arranged between the laser crystal rod and the quartz tube. By the adoption of the structure, due to the staggered arrangement, pump light does not enter a few axial positions of the crystal rod in a concentrated mode any more, but is dispersed in the axial direction; in this way, the absorption length of the pump light by the crystal rod is effectively lengthened, local energy accumulation is avoided, and heat sources in the crystal rod are distributed more evenly and axially.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-power all-solid-state laser, and particularly to a side-pumping structure with LD staggered arrangement. BACKGROUND

[0002] The side-pumping solid-state laser has been widely used in industrial processing, military, scientific research and other fields due to its high-power and high-efficiency laser output. The design of the pump structure, one of the core components, directly determines the output power, beam quality and reliability of the laser.

[0003] The traditional side-pumping structure usually arranges multiple groups of LD bar along the axis of the laser crystal rod, and uniformly distributes them on the same circumferential surface (for example, 12 or 16 bar evenly distributed per circle). Although this design is simple in structure, it has inherent shortcomings: Severe thermal lens effect: the pump light is strongly absorbed on the surface layer of the crystal rod, resulting in a huge temperature gradient between the axis and the edge, forming a strong thermal lens effect, shortening the thermal focal length and seriously degrading the beam quality.

[0004] Thermal birefringence: the huge thermal stress causes the crystal to produce birefringence effect, making the polarization state of the laser complex and unstable, affecting polarization-related applications.

[0005] "Bright center" phenomenon: due to the rapid absorption of pump light in the entrance section of the crystal rod, the gain is the highest in this area, and the laser oscillation first reaches the strongest here, resulting in an abnormally bright bright spot in the center of the final output spot, i.e. "bright center", which makes the light energy distribution extremely uneven, limiting its application in many fine processing fields.

[0006] Therefore, there is an urgent need for a new pump structure that can fundamentally improve the deposition and distribution of pump light energy in the crystal, reduce thermal load, and eliminate the bright center problem. SUMMARY

[0007] The purpose of the present application is to provide a side-pumping structure with LD staggered arrangement, which effectively lengthens the pump absorption length by a unique LD bar staggered arrangement, making the gain and heat distribution in the crystal rod more uniform, thereby significantly increasing the thermal focal length, suppressing thermal birefringence, and eliminating the "bright center" phenomenon of the output laser, ultimately obtaining high-power and high-beam-quality laser output.

[0008] In order to achieve the above object, the application provides a side-pumping structure with LD staggered arrangement, comprising a laser crystal rod, a pumping module and a cooling system, the pumping module is composed of several LD bar arrays, the LD bar arrays are closely surrounded outside the laser crystal rod, the LD bar array comprises several LD bars, the cooling system is integrated outside the pumping module, the laser crystal rod is sleeved with a quartz tube, the outer wall of the quartz tube is provided with a high reflection film, and the cooling water is arranged between the laser crystal rod and the quartz tube.

[0009] Preferably, the outer side of the laser crystal rod is provided with a water cooling plate, and the other end of the water cooling plate penetrates the quartz tube and is connected with the LD bar.

[0010] Preferably, the laser crystal rod selects a Nd:YAG rod with a diameter of 8mm and a length of 150mm, and the LD bar selects an 808nm LD bar with an output power of 100W.

[0011] Preferably, the cooling system adopts a precision micro-channel water cooling system to forcibly cool the LD bar array and the laser crystal rod, and the water temperature is controlled at 20±0.5℃.

[0012] Preferably, the LD bar array is arranged as ten circles, and the ten circles of LD bars are closely arranged in the axial direction, and each circle of LD bars is arranged as twelve or sixteen.

[0013] Preferably, the longitudinal arrangement mode of the LD bars in the same circle is as follows: The angle offset Δθ between the two adjacent LD bars in the transverse direction is: Δθ=360° / N; Wherein, N=12, Δθ=360° / 12=30° is obtained; The transverse installation angle of the nth LD bar is: θ n =(n-1) °; Wherein, n=1, 2, 3, …, 12.

[0014] Preferably, the longitudinal arrangement mode of the LD bars in the same circle is three, and the LD bar array adopts any one of the modes.

[0015] Preferably, the first longitudinal arrangement mode is that the longitudinal installation angle of the two adjacent LD bars in the same circle is: θ n ’=(n-1) °.

[0016] Preferably, the second longitudinal arrangement mode is that the longitudinal installation angles of the LD bars in the same circle are arranged in a periodic rule, and the longitudinal installation angles take 0°, 10°, 20° and 10° as a period.

[0017] Preferably, the third longitudinal arrangement mode is that the longitudinal installation angles of the LD bars in the same circle are arranged in a periodic rule, and the longitudinal installation angles take 0° and 20° as a period.

[0018] Therefore, the application has the following beneficial effects by adopting the above-mentioned side-pumping structure with LD staggered arrangement: 1. Pumping length is prolonged, and heat distribution is uniform: the staggered arrangement makes the pumping light not be concentrated on a few axial positions of the crystal rod, but be dispersed along the axial direction; this makes the absorption length of the pumping light by the crystal rod be effectively lengthened, avoids local energy accumulation, and makes the heat source distribution in the crystal rod be more uniform and axial.

[0019] 2. Thermal focal length is increased: due to the decrease of the temperature gradient, the thermal lens effect is greatly weakened, and the thermal focal length is significantly increased, which is beneficial to the design and stability of the resonant cavity, and directly leads to the improvement of the beam quality.

[0020] 3. Thermal birefringence effect is reduced: uniform heat distribution means that the thermal stress is reduced, thereby effectively inhibiting the thermal birefringence effect caused by the thermal stress, and improving the polarization purity of the laser.

[0021] 4. Elimination of "bright center": the problem of excessive concentration of gain at the inlet end of the crystal rod is fundamentally solved, the gain distribution of the entire gain region is more flat, so that a laser spot with uniform energy distribution is output, the disturbing "bright center" phenomenon is eliminated, and it is particularly suitable for laser processing applications requiring uniform light spot.

[0022] The technical solutions of the application will be further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 FIG. 1 is a structural schematic diagram of a side-pumping structure with LD staggered arrangement according to an embodiment of the application; Figure 2 FIG. 2 is a plane expansion schematic diagram of the staggered arrangement mode in the embodiment one of the application; Figure 3 FIG. 3 is a plane expansion schematic diagram of the staggered arrangement mode in the embodiment two of the application; Figure 4 FIG. 4 is a plane expansion schematic diagram of the staggered arrangement mode in the embodiment three of the application; REFERENCE NUMERALS 1. LD bar array; 2. High reflectivity film; 3. Laser crystal rod; 4. Quartz tube; 5. Cooling water. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] Example 1 like Figure 1 As shown, this invention provides a side-pumping structure using staggered LD (Laser Diode) arrays, including a laser crystal rod 3, a pump module, and a cooling system. The laser crystal rod 3 serves as the gain medium. The pump module consists of several rings of LD bar arrays 1, which tightly surround the outer side of the laser crystal rod 3. Each LD bar array 1 includes several LD ​​bars. The cooling system is integrated outside the pump module for efficient heat dissipation of the LD bar arrays 1. A quartz tube 4 is sleeved on the outer side of the laser crystal rod 3, and a high-reflectivity film 2 is disposed on the outer wall of the quartz tube 4. Cooling water 6 is disposed between the laser crystal rod 3 and the quartz tube 4. A water-cooled plate is disposed on the outer side of the laser crystal rod 3, and the other end of the water-cooled plate passes through the quartz tube 4 and connects to the LD bars.

[0027] Within the same circle, the 12 LD bars are not arranged symmetrically at uniform angular intervals of 360° / 12=30° in the traditional manner, but rather in a staggered arrangement strategy.

[0028] The specific misalignment method for LD bar array 1 is as follows: Set the total number of circles to M (e.g., M=10), and the number of LD bars per circle to N (e.g., N=12). Then, within the same circle, the lateral angular offset Δθ between two adjacent LD bars is: Δθ=360° / N. Substituting N=12, we get Δθ=360° / 12=30°. The lateral installation angle of the nth LD bar is θ.n = (n - 1) The longitudinal direction of the LD bar array 1 is not arranged in a straight line, but is staggered.

[0029] The staggered arrangement of the LD bar array 1 in this embodiment is as follows: The 12 LD bars of the first circle are arranged at an angle of θ n in the horizontal direction and an angle of θ n = (n - 1) The angle of the first LD bar: 0° (horizontal) + 0° (vertical); The angle of the second LD bar: 30° (horizontal) + 3° (vertical); The angle of the third LD bar: 60° (horizontal) + 6° (vertical); The angle of the fourth LD bar: 90° (horizontal) + 10° (vertical); The angle of the fifth LD bar: 120° (horizontal) + 12° (vertical); ... The angle of the twelfth LD bar: 330° (horizontal) + 33° (vertical).

[0030] The LD bars of the second, third, and tenth circles follow the same rule, but the starting angle can be offset by an integer to ensure optimal coverage of the overall arrangement. From a macroscopic point of view, this arrangement is equivalent to "stretching" and "spreading" the pump energy originally concentrated at one end of the crystal rod (at the entrance) axially to a longer area.

[0031] In this embodiment, the laser crystal rod 3 is a Nd:YAG rod with a diameter of Φ8mm and a length of 150mm. The pump module uses a 10-circle LD bar array 1, each circle consisting of 12 808nm LD bars with an output power of 100W, and the LD bars are installed on a water-cooled plate. The wavelength of the LD bars can be set to one of 808nm, 880nm, 976nm, or 940nm.

[0032] As shown in Figure 2 , the 12 LD bars in each circle are installed according to the staggered scheme described above, i.e., the horizontal and vertical installation angles of the first LD bar are both 0°, and the horizontal installation angles of adjacent LD bars are spaced by 30°, and the vertical installation angles are spaced by 3°, and the 10 LD bars are arranged closely in the axial direction, with a total pump length of about 120mm.

[0033] ​In this embodiment, the cooling system adopts a precise micro-channel water cooling system to force-cool the LD bar array 1 and the laser crystal rod 3, and the water temperature is controlled at 20±0.5°C.

[0034] In operation, the 10 turns of 120 LD bars simultaneously emit 808nm pump light to pump the Nd:YAG crystal rod from the side. Due to the unique staggered arrangement, the pump light energy is nearly uniformly absorbed on the length of 120mm of the crystal rod, avoiding the energy peak at the inlet end.

[0035] Embodiment Two The difference between this embodiment and Embodiment One is that the longitudinal arrangement of the LD bar array 1 is different.

[0036] In this embodiment, the staggered arrangement of the LD bar array 1 is as follows: The 12 LD bars of the first turn are installed at a horizontal angle of θ n , and the longitudinal installation angle is arranged periodically: The first LD bar angle: 0° (horizontal) + 0° (longitudinal); The second LD bar angle: 30° (horizontal) + 10° (longitudinal); The third LD bar angle: 60° (horizontal) + 20° (longitudinal); The fourth LD bar angle: 90° (horizontal) + 10° (longitudinal); The fifth LD bar angle: 120° (horizontal) + 0° (longitudinal); ... The twelfth LD bar angle: 330° (horizontal) + 10° (longitudinal).

[0037] The LD bars of the second turn, the third turn, and the tenth turn are also arranged according to this rule, but the starting angle can have an overall offset to ensure optimal coverage of the overall arrangement. From a macroscopic point of view, this arrangement is equivalent to "stretching" and "spreading" the pump energy originally concentrated at one end of the crystal rod (at the inlet) axially to a longer area.

[0038] As Figure 3 shown, the 12 LD bars in each turn are installed according to the aforementioned staggered scheme. That is, the horizontal installation angle of the first LD bar is 0°, and the horizontal installation angle of adjacent LD bars is spaced by 30°, and the longitudinal installation angle of the LD bars is arranged periodically, with 0°, 10°, 20°, and 10° as a period. The 10 turns of LD bars are closely arranged in the axial direction, and the total pump length is about 120mm.

[0039] During operation, 10 rings of 120 LD bars simultaneously emit 808nm pump light to pump the Nd:YAG crystal rod from the side. Due to the unique staggered arrangement, the pump light energy is absorbed almost uniformly along the 120mm length of the crystal rod, avoiding energy spikes at the entrance end.

[0040] Example 3 The difference between this embodiment and Embodiment 1 lies in the different vertical arrangement of the LD bar array 1.

[0041] In this embodiment, the staggered arrangement of the LD bar array 1 is as follows: The first ring of 12 LD bar strips is installed at a horizontal angle of θ. n The longitudinal installation angles are arranged according to a periodic rule: The first LD bar angle: 0° (horizontal) + 0° (vertical); The angle of the second LD bar: 30° (horizontal) + 20° (vertical); The angle of the third LD bar: 60° (horizontal) + 0° (vertical); The angle of the 4th LD bar: 90° (horizontal) + 20° (vertical); The fifth LD bar angle: 120° (horizontal) + 0° (vertical); ... The 12th LD bar angle: 330° (horizontal) + 0° (vertical).

[0042] The second, third, and up to the tenth LD bar strips follow the same rule, but their starting angles can be offset as a whole to ensure optimal coverage of the overall arrangement. From a macroscopic perspective, this arrangement is equivalent to axially "stretching" and "spreading" the pump energy that was originally concentrated at one end of the crystal bar (the entrance) to a longer region.

[0043] like Figure 4 As shown, the 12 LD bar strips in each ring are installed according to the aforementioned staggered scheme, that is, the lateral installation angle of the first LD bar strip is 0°, and the lateral installation angle interval of adjacent LD bar strips is 30°. The longitudinal installation angle of the LD bar strips is arranged in a periodic pattern, with a longitudinal installation angle of 0° and 20° as one cycle. The 10 rings of LD bar strips are closely arranged in the axial direction, and the total pumping length is about 120mm.

[0044] During operation, 10 rings of 120 LD bars simultaneously emit 808nm pump light to pump the Nd:YAG crystal rod from the side. Due to the unique staggered arrangement, the pump light energy is absorbed almost uniformly along the 120mm length of the crystal rod, avoiding energy spikes at the entrance end.

[0045] Example 4 The difference between this embodiment and Embodiment 1 is that the pump module uses a 10-ring LD bar array 1, with each ring consisting of 16 808nm LD bars with an output power of 100W, and the LD bars are mounted on a water-cooling plate. The LD bar array 1 is arranged in any of the methods in Embodiment 1, Embodiment 2, or Embodiment 3.

[0046] Test results show that, compared with a conventional pump module of the same power using a uniform arrangement (12 LD bar strips / ring, uniformly spaced at 30°), this invention: The maximum temperature on the surface of the crystal rod decreased by approximately 15%; The measured thermal focal length was extended by approximately 50%; The beam quality factor M of the output laser 2 Improved by approximately 30%; Most importantly, the energy distribution of the output light spot is uniform, and the "bright center" phenomenon is not observed at all.

[0047] Therefore, the present invention adopts a side pumping structure with staggered LD arrangement, which fundamentally solves the problem of excessive gain concentration at the crystal rod inlet end, making the gain distribution in the entire gain region flatter, thereby outputting a laser spot with uniform energy distribution, eliminating the troublesome "bright center" phenomenon, and is particularly suitable for laser processing applications that require a uniform spot.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A side pump structure employing staggered LD arrangement, characterized in that: The system includes a laser crystal rod, a pump module, and a cooling system. The pump module consists of several rings of LD bar arrays tightly surrounding the outside of the laser crystal rod. The LD bar array includes several LD ​​bars. The cooling system is integrated outside the pump module. A quartz tube is sleeved on the outside of the laser crystal rod. A high-reflectivity film is provided on the outer wall of the quartz tube. Cooling water is provided between the laser crystal rod and the quartz tube.

2. The side pumping structure with staggered LD arrangement according to claim 1, characterized in that: A water-cooled plate is provided on the outside of the laser crystal rod, and the other end of the water-cooled plate passes through the quartz tube and is connected to the LD bar.

3. The side pumping structure with staggered LD arrangement according to claim 1, characterized in that: The laser crystal rod is an Nd:YAG rod with a diameter of Φ8mm and a length of 150mm; the LD bar is an 808nm LD bar with an output power of 100W.

4. The side pumping structure with staggered LD arrangement according to claim 1, characterized in that: The cooling system employs a precision microchannel water cooling system to forcibly cool the LD bar array and the laser crystal rod, with the water temperature controlled at 20±0.5℃.

5. A side pumping structure with staggered LD arrangement according to claim 1, characterized in that: The LDbar array is configured as ten circles, with the ten circles of LDbars arranged closely along the axial direction, and each circle containing twelve or sixteen LDbars.

6. A side pumping structure with staggered LD arrangement according to claim 5, characterized in that: The longitudinal arrangement of LD bar strips within the same circle is set as follows: The lateral angular offset Δθ between two adjacent LD bars is: Δθ = 360° / N; Where N=12, we get Δθ=360° / 12=30°; The lateral installation angle of the nth LD bar is: i n =(n-1) °; Where n = 1, 2, 3, ..., 12.

7. A side pumping structure with staggered LD arrangement according to claim 6, characterized in that: There are three ways to arrange the LD bar strips in the same circle, and the LD bar strip array can be arranged in any of these ways.

8. A side pumping structure with staggered LD arrangement according to claim 7, characterized in that: The first longitudinal arrangement method is as follows: the longitudinal installation angle of two adjacent LD bar strips within the same circle is: i n '=(n-1) °。 9. A side pumping structure with staggered LD arrangement according to claim 8, characterized in that: The second longitudinal arrangement method is as follows: the longitudinal installation angles of the LD bar strips within the same circle are arranged according to a periodic rule, with the longitudinal installation angles in a cycle of 0°, 10°, 20°, and 10°.

10. A side pumping structure with staggered LD arrangement according to claim 9, characterized in that: The third longitudinal arrangement method is as follows: the longitudinal installation angles of the LD bar strips within the same circle are arranged according to a periodic rule, with the longitudinal installation angles in cycles of 0° and 20°.

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