Laser gain medium heat dissipation module

Abstract

The application relates to a laser gain medium heat dissipation module, which comprises a water inlet manifold, a cooling flow channel and a water outlet manifold. The water inlet manifold comprises a mixing area, a front nozzle and a diffusion area connected in sequence. The flow cross section of the diffusion area is smaller than that of the mixing area and larger than that of the front nozzle. The cooling flow channel is connected to the upstream of the diffusion area and has a flow cross section smaller than that of the diffusion area. The water outlet manifold comprises a converging area, a rear nozzle and a release area connected in sequence. The flow cross section of the converging area is smaller than that of the release area and larger than that of the rear nozzle. The converging area is connected to the downstream of the cooling flow channel and has a flow cross section larger than that of the cooling flow channel. The laser gain medium is arranged on one side of the cooling flow channel, the turbulent flow passes through the cooling surface of the laser gain medium, and the cooling surface of the laser gain medium is parallel to the flow direction of the turbulent flow. The application makes the heat conductivity of the cooling surface of the laser gain medium uniform and reduces the influence of the water flow longitudinal wave on the laser gain medium.

Description

Technical Field

[0001] This invention relates to the field of laser heat dissipation technology, and in particular to a laser gain medium heat dissipation module. Background Technology

[0002] A common cooling solution for the gain medium in high-power, high-energy disk lasers is an array jet cooling system. This typically involves arranging one or more nozzles on the back of the gain medium, using the cooling medium to impact it. If distilled water is used as the cooling medium at room temperature, to ensure stable operation, the water flow velocity on the cooling surface needs to be greater than 1.2 m / s, and the Reynolds number Re > 3500 to achieve a sufficient heat exchange rate. Because the pump beam size is relatively small (5–15 mm in diameter), an array jet cooling system requires arranging numerous nozzles within a small area, inevitably leading to stagnation points and uneven thermal conductivity, causing output beam distortion. Furthermore, due to the mechanical characteristics of water chillers, cost-effective chillers that achieve the required output water pressure and velocity often use mechanical pumps. Because the water flow rate to the gain medium is relatively large, the longitudinal wave vibrations of the chiller's output water can easily propagate to the gain medium, leading to instability in the amplified laser's directivity. Summary of the Invention

[0003] Therefore, it is necessary to provide a laser gain medium heat dissipation module with more uniform thermal conductivity and effective reduction of longitudinal wave vibration to address the above-mentioned technical problems.

[0004] The present invention provides a laser gain medium heat dissipation module, comprising:

[0005] The water inlet manifold includes a mixing zone, a front nozzle, and a diffuser zone connected in sequence. The flow cross-section of the diffuser zone is smaller than that of the mixing zone but larger than that of the front nozzle.

[0006] The cooling channel is connected upstream to the diffusion zone, and its flow cross-section is smaller than that of the diffusion zone.

[0007] The drain manifold includes a convergence zone, a rear nozzle, and a release zone connected in sequence. The flow cross-section of the convergence zone is smaller than that of the release zone and larger than that of the rear nozzle. The upstream of the convergence zone is connected to the downstream of the cooling channel, and its flow cross-section is larger than that of the cooling channel.

[0008] The laser gain medium is disposed on one side of the cooling channel, and turbulent flow passes through the cooling surface of the laser gain medium, with the cooling surface of the laser gain medium parallel to the turbulent flow direction.

[0009] In one embodiment, the cooling channel is a flat channel, and the orthographic projection of the cooling surface of the laser gain medium falls into the cooling channel.

[0010] In one embodiment, the heat dissipation module includes a body and a fixing member. The mixing zone, front nozzle, rear nozzle and release zone are disposed in the body. The fixing member has a light-transmitting hole. The laser gain medium is installed in the light-transmitting hole. The fixing member is installed on the body and forms the diffusion zone, cooling channel and convergence zone between the fixing member and the body.

[0011] In one embodiment, the body has a recessed portion, the recessed portion having regions corresponding to the diffusion region, cooling channel, and convergence region, respectively.

[0012] In one embodiment, the body has a flow channel pad disposed in the region corresponding to the cooling flow channel.

[0013] In one embodiment, the outlet of the front nozzle is located in the region corresponding to the diffusion zone, the inlet of the front nozzle extends to the mixing zone, the inlet of the rear nozzle is located in the region corresponding to the convergence zone, and the outlet of the rear nozzle extends to the release zone.

[0014] In one embodiment, the fixing member includes a first fixing plate and a second fixing plate, the light-transmitting hole includes a front window and a rear window, the front window is located on the first fixing plate, the rear window is located on the second fixing plate, the size of the front window is smaller than the size of the rear window, the bottom of the rear window has a flange, the laser gain medium is installed in the rear window and supported on the flange, the first fixing plate is fixed on the second fixing plate and presses the laser gain medium.

[0015] In one embodiment, an annular groove is formed on the side of the flange opposite to the first fixing piece, and an indium wire is embedded in the annular groove.

[0016] In one embodiment, the turbulent thickness of the cooling channel section where the laser gain medium is located is not less than 0.1 mm.

[0017] The aforementioned laser gain medium heat dissipation module maintains a high Reynolds number and turbulence state as the cooling water flows through the cooling surface of the laser gain medium by setting front nozzles and rear nozzles upstream and downstream of the cooling channel, respectively. This ensures high heat dissipation efficiency and uniform cooling water and thermal conductivity on the laser gain medium cooling surface. At the same time, the structure of the water inlet manifold causes the cooling water entering in laminar flow to experience high and concentrated frictional resistance when passing through the nozzles, reducing the impact of longitudinal waves generated by the mechanical water pump on the laser gain medium. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is an exploded view of a laser gain medium heat dissipation module according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of a laser gain medium heat dissipation module according to an embodiment of the present invention;

[0021] Figure 3 for Figure 1 Another schematic diagram of the laser gain medium heat dissipation module in the embodiment;

[0022] Figure 4 for Figure 1 A schematic diagram of the main body of the laser gain medium heat dissipation module;

[0023] Figure 5 for Figure 1 A cross-sectional view of the main body of the laser gain medium heat dissipation module;

[0024] Figure 6 for Figure 1 A magnified view of part A in the middle;

[0025] Figure 7 for Figure 1 A magnified view of part B in the middle.

[0026] Figure label:

[0027] 100. Body; 110. Inlet manifold; 112. Mixing zone; 114. Front nozzle; 116. Diffusion zone; 120. Cooling channel; 130. Drain manifold; 132. Convergence zone; 134. Rear nozzle; 136. Release zone; 140. Recess; 150. Flow channel gasket; 200. Fixing element; 210. Light transmission hole; 212. Front window; 214. Rear window; 220. First fixing plate; 230. Second fixing plate; 242. Flange; 234. Annular groove; 236. Settlement groove; 50. Laser gain medium. Detailed Implementation

[0028] 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 embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this specification are for illustrative purposes only and do not represent the only possible implementation.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0033] Yb:YAG crystals have seen increased application in high-power and high-energy laser systems in recent years due to their long upper-level lifetime, suitable absorption bandwidth, and relatively high thermal conductivity among various gain media. When used as a gain medium, approximately 11% of the pump energy is applied as a quantum defect to the laser gain region. In high-energy laser systems at the 100 mJ (millijoule) level, due to design limitations, depending on the specific design specifications, 31-42% of the pump energy is absorbed as fluorescence by the surrounding cladding or anti-spontaneous emission materials. In these applications, the inherent thermal conductivity of Yb:YAG is far from sufficient to effectively dissipate this heat, resulting in a large temperature gradient within the crystal, affecting the beam quality, and in severe cases, causing crystal fragmentation. Therefore, effective thermal management is one of the core technologies for the normal operation of such laser systems.

[0034] To achieve single-pulse energy of 100mJ to 1J and 100Hz-level laser amplification, the gain region of the laser gain medium needs to withstand a minimum of 600W / cm². 2 Pump beam power. A common heat dissipation design for achieving high throughput is to weld the crystal onto a material with high thermal conductivity or a matching coefficient of thermal expansion (such as diamond or tungsten-copper alloy), but this introduces additional system complexity and higher costs. Another common crystal cooling solution for high-power, high-energy disk lasers is array jet, which typically involves arranging one or more nozzles on the back of the crystal and using a cooling medium to impact the crystal. If distilled water is used as the cooling medium at room temperature, to ensure stable operation of the gain medium at room temperature, the water flow velocity on the cooling surface of the gain medium needs to be greater than 1.2 m / s, and the Reynolds number Re > 3500 needs to be guaranteed to achieve a sufficient heat exchange rate. Due to the small size of the pump beam (5-15 mm in diameter), if an array jet solution is used, it is difficult to avoid the formation of stagnation points due to the need to arrange many nozzles in a small area, leading to uneven thermal conductivity and causing output beam deformation. At the same time, due to the mechanical characteristics of water chillers, cost-effective water chillers that can achieve the required output water pressure and flow rate often use mechanical water pumps. Since the water flow rate output to the gain medium is relatively large, the longitudinal wave vibration of the water output from the water chiller is more likely to propagate to the gain medium, which can easily lead to unstable laser directivity after amplification.

[0035] To address the aforementioned technical problems, this invention provides a laser gain medium heat dissipation module.

[0036] The following is combined with Figures 1 to 7 The laser gain medium heat dissipation module of the present invention is described.

[0037] like Figures 1 to 7 As shown, in one embodiment, a laser gain medium heat dissipation module includes an inlet manifold 110, a cooling channel 120, and a drain manifold 130.

[0038] The inlet manifold 110 includes a mixing zone 112, a front nozzle 114, and a diffuser zone 116 connected in sequence. The flow cross-section of the diffuser zone 116 is smaller than that of the mixing zone 112 but larger than that of the front nozzle 114. The upstream of the mixing zone 112 is the inlet 111. Water enters from the inlet 111, passes through the mixing zone 112, and enters the diffuser zone 116 from the front nozzle 114. Optionally, multiple front nozzles 114 are provided and arranged in parallel at equal intervals. The mixing zone 112 is columnar, and the axial direction of the columnar mixing zone 112 is parallel to the plane containing the multiple front nozzles 114, thereby ensuring that the flow velocity of the water entering each front nozzle 114 from the mixing zone 112 is consistent, thus ensuring that the flow rate entering the diffuser zone 116 from each front nozzle 114 is consistent. The flow cross-section of the mixing zone 112 is larger than that of the inlet 111.

[0039] The upstream of the cooling channel 120 is connected to the diffusion zone 116, and the flow cross section of the cooling channel 120 is smaller than the flow cross section of the diffusion zone 116.

[0040] The drain manifold 130 includes a convergence zone 132, a rear nozzle 134, and a release zone 136 connected in sequence. The flow cross-section of the convergence zone 132 is smaller than that of the release zone 136 but larger than that of the rear nozzle 134. The upstream of the convergence zone 132 connects to the downstream of the cooling channel 120, and its flow cross-section is larger than that of the cooling channel 120. The downstream of the release zone 136 is the outlet 131. Optionally, multiple rear nozzles 134 are provided and arranged in parallel at equal intervals. The orifice diameter, length, and number of the rear nozzles 134 are the same as those of the front nozzles 114. The release zone 136 is cylindrical, and the axial direction of the cylindrical release zone 136 is parallel to the plane where the multiple rear nozzles 136 are located, thereby ensuring that the flow velocity of the water entering each rear nozzle 134 from the convergence zone 132 is consistent, thus ensuring that the flow rate entering the release zone 136 from each rear nozzle 134 is consistent. The flow cross-section of the release zone 136 is equal to that of the mixing zone 112. The flow cross section of the release zone 136 is larger than that of the outlet 131.

[0041] The laser gain medium 50 is disposed on one side of the cooling channel 120, and turbulent flow passes through the cooling surface of the laser gain medium 50, with the cooling surface of the laser gain medium 50 parallel to the turbulent flow direction.

[0042] The front nozzle 114 and rear nozzle 134 act as damping orifices as water flows through them. When water carrying longitudinal waves propagates through the damping orifice, the structure within the orifice causes energy loss due to friction and eddies in the fluid. These losses cause the wave energy to gradually convert into heat energy, thereby reducing the amplitude and frequency of vibration to reduce impact. The damping orifice is typically a small, fixed, elongated orifice. Fluid flow through the damping orifice is generally in a laminar flow state; the flow rate is directly proportional to the pressure difference before and after the orifice (not the square root of the relationship for thin-walled orifices), inversely proportional to the kinematic viscosity and length, and directly proportional to the fourth power of the diameter. The formula for the damping orifice flow rate is:

[0043]

[0044] In the formula, all physical quantities are in SI units, Q is the flow rate, d is the diameter of the damping orifice, Δp is the pressure difference across the orifice, μ is the viscosity coefficient, and L is the orifice diameter.

[0045] For a longitudinal wave with amplitude A and angular frequency ω The rate of change of flow rate after the damping orifice is inversely proportional to the fourth power of the damping orifice diameter. Testing showed that using a damping orifice with a diameter d = 2 mm and an aspect ratio of 1.5 as the nozzle is sufficient to achieve laser pointing vibration of less than 7 μrad, meeting the requirements. To ensure consistent flow rate across all damping orifices, a mixing zone 112 and a release zone 136 are provided on the inlet and outlet sides, ensuring that the output flow rate of nozzles located at the edges is consistent with that of nozzles located at the center.

[0046] The aforementioned laser gain medium heat dissipation module, by setting a front nozzle 114 and a rear nozzle 134 upstream and downstream of the cooling channel 120 respectively, serves as a turbulence generator and controls the length of the diffusion section. This ensures that the cooling water maintains a high Reynolds number and turbulent state when flowing through the cooling surface of the laser gain medium, thereby maintaining high heat dissipation efficiency. Furthermore, the cooling water on the cooling surface of the laser gain medium 50 is relatively uniform, and the thermal conductivity is also relatively uniform. At the same time, the structure of the water inlet manifold 110 causes the cooling water entering in a laminar flow to experience high and concentrated frictional resistance when passing through the nozzle, reducing the impact of the longitudinal waves of the water flow generated by the mechanical water pump on the laser gain medium 50.

[0047] In this embodiment, the cooling channel is a flat channel, and the orthographic projection of the cooling surface of the laser gain medium 50 falls within the cooling channel. The flat channel makes the water flow through the cooling surface of the laser gain medium 50 more uniform, resulting in more uniform thermal conductivity.

[0048] In this embodiment, the heat dissipation module includes a body 100 and a fixing member 200. A mixing zone 112, a front nozzle 114, a rear nozzle 134, and a release zone 136 are disposed in the body. The fixing member 200 has a light-transmitting hole 210, and a laser gain medium 50 is installed in the light-transmitting hole 210. The fixing member 200 is mounted on the body 100, and a diffusion zone 116, a cooling channel 120, and a convergence zone 132 are formed between the fixing member 200 and the body 100. The outlet of the front nozzle 114 is located in the area corresponding to the diffusion zone 116, and the inlet of the front nozzle 114 extends to the mixing zone 112. The inlet of the rear nozzle 134 is located in the area corresponding to the convergence zone 132, and the outlet of the rear nozzle 134 extends to the release zone 136. When fabricating the mixing zone 112 and the release zone 136 on the body 100, a through hole is opened from one side of the body 100 to the other side, and then the two ends of the through hole are sealed with an interference fit water plug, thereby forming the mixing zone 112 or the release zone 136.

[0049] The body 100 has a recess 140, which has regions corresponding to the diffusion region 116, the cooling channel 120, and the convergence region 132, respectively. The body 100 also has a channel shim 150, which is disposed in the region corresponding to the cooling channel 120 and fixed with countersunk screws. The thickness of the cooling channel 120 can be adjusted by adjusting the thickness of the channel shim 150, and the area parallel between the channel shim 150 and the cooling surface of the laser gain medium 50 is the effective heat dissipation area. Preferably, the thickness of the cooling channel 120 is less than 0.1 mm.

[0050] In this embodiment, the fixing member 200 includes a first fixing plate 220 and a second fixing plate 230. The light transmission hole 210 includes a front window 212 and a rear window 214. The front window 212 is located on the first fixing plate 220, and the rear window 214 is located on the second fixing plate 230. The size of the front window 212 is smaller than the size of the rear window 214. The bottom of the rear window 214 has a flange 232. The laser gain medium 50 is installed in the rear window 214 and supported on the flange 232. The second fixing plate 230 has symmetrically arranged grooves 236 at the edge of the rear window 214 to facilitate the installation or removal of the laser gain medium 50. The first fixing plate 220 is fixed on the second fixing plate 230 and presses the laser gain medium 50 tightly.

[0051] An annular groove 234 is formed on the side of the flange 232 opposite to the first fixing plate 220, and an indium wire is embedded in the annular groove. The indium wire seals the edge of the laser gain medium 50. After deformation, the indium wire covers the gap at the edge of the laser gain medium 50 and provides sufficient contact between the edge of the laser gain medium 50 and the heat sink to remove residual heat from the edge material of the laser gain medium 50. Optionally, the laser gain medium 50 is a thick disk-shaped Yb:YAG laser crystal.

[0052] Through fluid dynamics simulation of the flow channel, when the water flow rate reaches the required minimum value of 2.6 L / min, the Reynolds number near the cooling surface in the cooling channel 120 of this invention reaches the turbulent boundary condition Re > 3500. At this point, the flow velocity is 0.9 m / s, the boundary layer thickness available for heat exchange is > 0.5 mm, and with the outlet water temperature being 1 °C higher than the inlet water temperature, the total heat dissipation capacity is 42 W, and the total heat dissipation surface area is 0.96 cm². 2 Specific heat dissipation power 44W / cm 2 .

[0053] Compared to welding high thermal conductivity materials or fabricating array jets or microchannels, this invention is easier to manufacture and more readily industrialized, contributing to further reductions in the mass production cost of high-energy laser systems. In practical applications, this invention can support 1000W, 1.2ms, 50Hz, 3.0mm diameter lasers with 8% residual heat, resulting in an equivalent heat dissipation power of 41W / cm². 2 Pump power density 520W / cm² 2 Pump-type beams offer more uniform heat dissipation and higher quality emitted beams. Furthermore, they eliminate the yield rate limitations associated with soldering methods, resulting in high cost-effectiveness in engineering applications.

[0054] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A laser gain medium heat dissipation module, characterized in that, include: The water inlet manifold includes a mixing zone, a front nozzle, and a diffuser zone connected in sequence. The flow cross-section of the diffuser zone is smaller than that of the mixing zone but larger than that of the front nozzle. The cooling channel is connected upstream to the diffusion zone, and its flow cross-section is smaller than that of the diffusion zone. The drain manifold includes a convergence zone, a rear nozzle, and a release zone connected in sequence. The flow cross-section of the convergence zone is smaller than that of the release zone and larger than that of the rear nozzle. The upstream of the convergence zone is connected to the downstream of the cooling channel, and its flow cross-section is larger than that of the cooling channel. The laser gain medium is disposed on one side of the cooling channel, and turbulent flow passes through the cooling surface of the laser gain medium, with the cooling surface of the laser gain medium parallel to the turbulent flow direction.

2. The laser gain medium heat dissipation module according to claim 1, characterized in that, The cooling channel is a flat channel, and the orthographic projection of the cooling surface of the laser gain medium falls into the cooling channel.

3. The laser gain medium heat dissipation module according to claim 1, characterized in that, The heat dissipation module includes a body and a fixing component. The mixing zone, front nozzle, rear nozzle and release zone are disposed in the body. The fixing component has a light-transmitting hole. The laser gain medium is installed in the light-transmitting hole. The fixing component is installed on the body and forms the diffusion zone, cooling channel and convergence zone between the fixing component and the body.

4. The laser gain medium heat dissipation module according to claim 3, characterized in that, The body has a concave portion, and the concave portion has regions corresponding to the diffusion region, cooling channel, and convergence region, respectively.

5. The laser gain medium heat dissipation module according to claim 4, characterized in that, The body has a flow channel gasket, which is disposed in the area corresponding to the cooling flow channel.

6. The laser gain medium heat dissipation module according to claim 4, characterized in that, The outlet of the front nozzle is located in the region corresponding to the diffusion zone, the inlet of the front nozzle extends to the mixing zone, the inlet of the rear nozzle is located in the region corresponding to the convergence zone, and the outlet of the rear nozzle extends to the release zone.

7. The laser gain medium heat dissipation module according to claim 3, characterized in that, The fixing component includes a first fixing plate and a second fixing plate. The light-transmitting hole includes a front window and a rear window. The front window is located on the first fixing plate, and the rear window is located on the second fixing plate. The size of the front window is smaller than the size of the rear window. The bottom of the rear window has a flange. The laser gain medium is installed inside the rear window and supported on the flange. The first fixing plate is fixed on the second fixing plate and presses the laser gain medium.

8. The laser gain medium heat dissipation module according to claim 7, characterized in that, The flange has an annular groove on the side opposite to the first fixing piece, and an indium wire is embedded in the annular groove.

9. The laser gain medium heat dissipation module according to any one of claims 1 to 8, characterized in that, The turbulent thickness of the cooling channel section where the laser gain medium is located is not less than 0.1 mm.

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