Laser with enhanced high-power pump beam quality based on multi-layer heat transfer

Abstract

The present invention belongs to the field of solid-state lasers, and specifically relates to a laser that achieves high-power pump beam quality enhancement based on multi-layer heat transfer, including a pump module, a pump shaping coupling module, a multi-layer crystal, a corner cube prism, an output mirror, and a cooling device. The multi-layer crystal adopts a high thermal conductivity diamond film to achieve rapid lateral diffusion of heat, alleviate local heat accumulation and temperature rise, reduce wavefront distortion and thermal lens effect caused by thermally induced refractive index changes, and improve laser mode stability. The corner cube prism serves as a resonant cavity mirror, which can automatically compensate for angle deviation, optimize intracavity mode matching, and cooperate with the zigzag total internal reflection path in the crystal to further balance the heat-affected zone and improve the light field distribution, significantly improving the beam uniformity, stability and TEM 00 Mode quality. This structure is highly adaptable and suitable for a variety of wavelengths, pumping methods, and thermal loads, helping lasers achieve miniaturization, high integration, and high-performance output.

Description

Technical Field

[0001] The present invention relates to the technical field of solid lasers, and in particular to a laser capable of achieving high-power pump beam quality enhancement based on multi-layer heat transfer. Background Art

[0002] High-power solid-state lasers have extensive and in-depth applications in materials processing, laser cleaning, laser surgery, laser guidance, lidar, and other industrial, medical, and military fields. Under high-power end-pumping conditions, the longitudinal absorption non-uniformity of the pump light in the laser medium can lead to significant thermal effects. Water cooling is typically used to protect the laser medium from excessive temperature damage. However, severe thermal effects exacerbate the laser's non-axisymmetry and produce thermal lensing, which changes the laser beam propagation path, causing resonant cavity detuning and affecting the quality of the laser output. Thermal stress can even directly damage the laser crystal.

[0003] Bonding crystals is often used to reduce thermal effects, or thermal boosting is employed to effectively suppress thermal relaxation. However, as power increases, the laser's higher-order modes inevitably oscillate, and the generation of a large number of non-fundamental modes can seriously affect beam quality. To maintain the laser's low-order modes, high-order modes must be effectively restricted. However, this restriction inevitably weakens the laser output power, resulting in lower end-pumped output power.

[0004] Therefore, side pumping is often used to obtain high power output. The side pumping structure can provide a larger pumping area, reduce the power density of a single pump light source, and thus improve the tolerance of the crystal. However, it is more likely to cause beam mode distortion. 4f imaging system or double rod cascade structure is often used to compensate for thermal effects and optimize the resonant cavity to obtain TEM. 00 module output, but its structure is very complex. Summary of the Invention

[0005] (1) Technical problems solved

[0006] In view of the shortcomings of the prior art, the present invention provides a laser that achieves high-power pump beam quality enhancement based on multi-layer heat transfer, solving the problems raised in the above background technology.

[0007] (2) Technical solution

[0008] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0009] A laser that achieves high-power pump beam quality enhancement based on multi-layer heat transfer, including a pump module, a pump shaping coupling module, a multi-layer crystal, a corner cube, an output mirror, and a cooling device;

[0010] The pump module generates pumping light to excite the multi-layer crystal, provides stable energy, and achieves population inversion of the crystal. It is located directly above the multi-layer crystal.

[0011] The pump shaping coupling module is located between the light outlet of the pump module and the multi-layer crystal, and the pump light is shaped by the pump shaping coupling module and then injected into the multi-layer crystal;

[0012] The multi-layer crystal is formed by stacking crystal materials and diamond films. The laser incident surface of the multi-layer crystal is a roughened crystal material to avoid parasitic oscillations. The interior of the crystal is a diamond film. The end faces of the multi-layer crystal are coated with a laser anti-reflection film, and the remaining surfaces are coated with diamond films to facilitate and quickly remove heat from the crystal. The oscillating laser propagates in a zigzag shape through total internal reflection inside the multi-layer crystal, so that the uneven thermal effects of the laser in different areas in the y direction offset each other, thereby achieving the purpose of reducing or even eliminating the thermal lens effect.

[0013] The corner cube is placed on the left side of the multi-layer crystal, with its center on the same horizontal line as the center of the multi-layer crystal, and arranged in a vertical direction, that is, its main axis is perpendicular to the horizontal line. The corner cube, through the light path folding and beam homogenization effect, combined with the excellent heat dissipation performance of the multi-layer crystal, not only ensures the consistency of beam propagation, but also significantly improves the energy distribution uniformity under high-power pumping, which helps to improve the beam quality and operation stability of the laser output;

[0014] The output mirror is placed on the left side of the multi-layer crystal, with its center on the same horizontal line as the center of the multi-layer crystal and parallel to the corner cube prism to form a resonant cavity;

[0015] The cooling device is located below the multi-layer crystal and is designed to dissipate heat efficiently and ensure that the crystal maintains a stable temperature distribution during operation.

[0016] Furthermore, the pump module is used to provide pump energy to the laser gain medium, and can be a semiconductor laser diode LD, a flash lamp pump module, or a fiber-coupled pump module.

[0017] Furthermore, the multi-layer crystal serves as a laser gain medium, can effectively absorb pump light and achieve population inversion to generate laser output. The gain layer can optionally use solid laser crystals doped with rare earth elements such as Nd³⁺, Yb³⁺, and Er³⁺, such as Nd:YAG, Yb:YAG, and Er:YAG, to provide efficient laser gain.

[0018] Furthermore, the cooling device may be a water-cooled heat sink, a static gas conduction cooling device, a flowing air-water mixed cooling device, or a semiconductor cooler TEC cooling device.

[0019] Furthermore, by combining corner cube prisms with multi-layer crystals, the light beam propagates in a uniform zigzag path within the resonant cavity, which not only improves beam shaping and uniformity but also significantly suppresses wavefront distortion caused by heat. The corner cube prism can compensate for cavity mirror installation errors and improve intra-cavity mode matching. Combined with the lateral heat diffusion structure of the multi-layer crystal, it effectively eliminates the problem of beam quality degradation caused by longitudinal temperature gradients, thereby obtaining highly stable, high-quality output lasers.

[0020] An application method for a laser that achieves high-power pump beam quality enhancement based on multi-layer heat transfer, characterized in that the method comprises:

[0021] S1: The pump module emits pump light, which is uniformly shaped by the pump shaping coupling module and then pumps the multi-layer crystal;

[0022] S2: The multi-layer crystal absorbs the pump light, causing population inversion and stimulated emission, generating laser light. At the same time, the crystal cut angle causes the laser light to be totally reflected inside the crystal, oscillating stably in a zigzag pattern in the resonant cavity composed of the corner cube prism and the output mirror.

[0023] S3: The high thermal conductivity and thermal diffusivity of the diamond film in the multi-layer crystal rapidly conducts heat deposited in the gain medium due to incomplete pump absorption, quantum defects, non-radiative transitions, and stimulated scattering to the cooling device and promptly removes it, effectively suppressing the formation of longitudinal temperature gradients. At the same time, surface roughening eliminates spontaneous radiation oscillations, significantly improving the output beam quality and the operational stability of the laser system.

[0024] S4: Using a corner cube as a resonant cavity mirror and taking advantage of its special reflective properties to automatically compensate for some angular errors can effectively reduce energy loss caused by slight detuning of the cavity mirror. This structure can enhance intracavity mode matching, optimize light field distribution, and improve light field unevenness caused by gain non-uniformity or thermal effects, thereby suppressing mode competition and significantly improving the stability and beam quality of the output beam.

[0025] The present invention provides a laser that achieves high-power pump beam quality enhancement based on multi-layer heat transfer. By combining a multi-layer crystal structure with a corner cube prism, the system's thermal management capability and beam quality control level are significantly improved. The multi-layer crystal utilizes a high-thermal-conductivity diamond film to achieve rapid lateral diffusion of heat within the crystal, extending the heat conduction path and effectively alleviating local heat accumulation and overall temperature rise under high-power working conditions. By precisely designing the number and spatial distribution of the layers, the refractive index gradient change caused by heat can be effectively suppressed, reducing wavefront distortion and thermal lensing effects, thereby improving the stability and consistency of the laser mode. At the same time, the corner cube prism, as a resonant cavity mirror structure, not only achieves efficient beam reflection and uniform distribution, but also automatically compensates for slight angular deviations of the cavity mirror, optimizing intra-cavity mode matching and light field coupling. The corner cube prism guides the light beam to propagate multiple times along a symmetrical path, forming a coordinated regulation with the zigzag total internal reflection path of the multi-layer crystal, further balancing the heat-affected zone and improving the light field distribution, significantly improving the uniformity, stability and TEM of the output beam. 00 Mode fidelity; this combined structure has good adaptability and scalability, and is suitable for a variety of wavelengths, pumping methods and thermal load conditions, which helps to achieve miniaturization, high integration and high-performance output of lasers, and meet complex and diverse application requirements.

[0026] (3) Beneficial effects

[0027] Compared with the prior art, the laser of the present invention, which realizes high-power pump beam quality enhancement based on multi-layer heat transfer, has the following beneficial effects:

[0028] The present invention significantly improves the thermal management capability and beam quality control level of the system through the synergistic combination of multi-layer crystals and corner cube prisms.

[0029] An ultra-thin, highly thermally conductive diamond film is embedded inside the multi-layer crystal to construct a lateral heat conduction channel, which allows the heat generated during the pumping process to be quickly transferred to the cooling device, significantly reducing heat accumulation, inhibiting the thermal lens effect and refractive index gradient change, and fundamentally improving the wavefront distortion and laser mode thermal mismatch problems.

[0030] As a cavity mirror component, the corner cube prism not only has multi-faceted high-precision reflection function, but can also adaptively compensate for slight angular deviations of the cavity mirror and optimize the light field distribution of the cavity.

[0031] Its special reflection path guides the laser to propagate symmetrically in a zigzag shape in the multi-layer crystal, further balancing the heat load distribution inside the crystal, forming a synergistic effect with the multi-layer structure, and effectively improving the beam uniformity and system stability.

[0032] This combined structure not only achieves high-power, high-beam-quality output, but also has good structural adjustability and material compatibility. It can flexibly adjust the number of stacked layers, crystal type, and optical cavity parameters according to specific application requirements. It is suitable for high-performance laser systems with different wavelengths, pumping methods, and heat dissipation conditions, providing strong technical support for the integration, compactness, and high-quality output of high-power solid-state lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the overall structure of a laser that achieves high-power pump beam quality enhancement based on multi-layer heat transfer;

[0034] Figure 2 This is a schematic diagram of the length of the multi-layer heat transfer crystal of the present invention;

[0035] Figure 3 This is a schematic diagram of the multi-layer heat transfer crystal structure of the present invention.

[0036] In the figure: 1. Pump module; 2. Pump shaping coupling module; 3. Multi-layer crystal; 4. Corner cube prism; 5. Output mirror; 6. Cooling device. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] Example

[0039] like Figure 1 As shown, a laser for achieving high-power pump beam quality enhancement based on multi-layer heat transfer includes a pump module 1, a pump shaping coupling module 2, a multi-layer crystal 3, a corner cube prism 4, an output mirror 5, and a cooling device 6;

[0040] The pump module 1 generates pumping light to excite the multi-layer crystal 3, provides stable energy, and achieves population inversion of the crystal. It is located directly above the multi-layer crystal 3.

[0041] The pump shaping coupling module 2 is located between the light outlet of the pump module 1 and the multi-layer crystal 3. The pump light is shaped by the pump shaping coupling module 2 and then injected into the multi-layer crystal 3.

[0042] The multi-layer crystal 3 is formed by stacking diamond film and crystal material. The laser incident surface of the multi-layer crystal 3 is a crystal material with a roughened surface to avoid parasitic oscillation. The interior of the crystal is a diamond film. The end face of the multi-layer crystal 3 is coated with a laser anti-reflection film, and the remaining surfaces are coated with diamond film. The heat deposited inside the multi-layer crystal 3 is transferred along the diamond film in the xz plane to the diamond films in the xy and yz planes outside the crystal, and then transferred to the xz surface of the bottom of the crystal immediately connected to the cooling device 6. The heat is finally taken away by the cooling device 6. The oscillating laser propagates in a zigzag shape through total internal reflection inside the multi-layer crystal 3, so that the uneven thermal effects of the laser in different areas in the y direction offset each other, thereby achieving the purpose of weakening or even eliminating the thermal lens effect.

[0043] Corner cube 4 is positioned to the left of multi-layer crystal 3, with its center aligned horizontally with the center of multi-layer crystal 3 and arranged vertically, with its principal axis perpendicular to the horizontal line. By folding the optical path and homogenizing the beam, combined with the excellent heat dissipation performance of multi-layer crystal 3, corner cube 4 not only ensures beam propagation consistency but also significantly improves energy distribution uniformity under high-power pumping, contributing to improved laser output beam quality and operational stability.

[0044] The output mirror 5 is placed on the left side of the multi-layer crystal 3, with its center on the same horizontal line as the center of the multi-layer crystal 3 and parallel to the corner cube prism 4, forming a resonant cavity;

[0045] The cooling device 6 is located below the multi-layer crystal 3 and is intended to dissipate heat efficiently and ensure that the crystal maintains a stable temperature distribution during operation;

[0046] Optionally, the pump module 1 is used to provide pump energy to the laser gain medium, and can be a semiconductor laser diode LD, a flash lamp pump module, a fiber-coupled pump module, etc.;

[0047] Optionally, the multi-layer crystal 3 serves as a laser gain medium, capable of effectively absorbing pump light and achieving population inversion to generate laser output. The gain layer may be a solid laser crystal doped with rare earth elements such as Nd³⁺, Yb³⁺, or Er³⁺, such as Nd:YAG, Yb:YAG, or Er:YAG, to provide efficient laser gain.

[0048] Optionally, the cooling device 6 may be a water-cooled heat sink, a static gas conduction cooling device, a flowing air-water mixed cooling device, or a semiconductor cooler TEC cooling device. Under high power, water cooling is the best cooling method.

[0049] like Figure 2As shown, in the embodiment, there is a fixed geometric relationship between the total length L of the multi-layer crystal and the propagation height h of the light in the crystal. Taking the YAG crystal as an example, assuming its cutting angle is θ1, combined with the refractive index relationship between air and crystal, according to Snell's law, it can be obtained:

[0050]

[0051] According to the trigonometric function relationship: θ3=90°+θ2-θ1, θ4=θ1-θ2. Figure 2 The calculated length of the AB segment shown is:

[0052]

[0053] The calculated lengths of segments BC and CD are:

[0054]

[0055] The calculated length of the DE segment is:

[0056]

[0057] The total length L of the multi-layer crystal is set to Figure 2 The length of the AE segment shown can be expressed as:

[0058]

[0059] Where n is a natural number, indicating that the laser undergoes a complete total reflection process inside the crystal, that is, the length of the crystal is BD. According to the total reflection angle, θ4 is greater than 41.5°. After substituting the parameters and simplifying, the relationship between the total length L and the propagation height h is obtained as follows:

[0060]

[0061] Where θ1>72°.

[0062] like Figure 3 As shown, in some embodiments, in order to further optimize the multi-layer crystal structure to meet the requirements for beam quality under high power pumping conditions. Figure 3 As shown in (a), in a modulated pump laser, the laser peak power is high and the heat is concentrated on the pump surface. The amount of diamond film with high thermal conductivity is increased locally to reduce thermal resistance and improve heat transfer efficiency. Figure 3 As shown in (b), in a continuous pump laser, since the pump light is continuously pumping, the heat accumulation time is long, which increases the distribution distance of the diamond film and makes the heat distribution more uniform; Figure 3 As shown in (c), it can be used for double-ended pump laser; Figure 3As shown in (d), increasing the number of thin films on the xy plane increases heat transfer efficiency. The optimized multi-layer crystal structure can specifically improve the crystal's heat dissipation capacity, maintaining stable and efficient beam quality under high-power pumping conditions, laying a solid foundation for the development of high-performance lasers.

[0063] An application method for achieving high-power pump beam quality enhancement of a laser based on multi-layer heat transfer, the method comprising:

[0064] S1: Pump module 1 emits pump light, which is uniformly shaped by pump shaping coupling module 2 and then pumps multi-layer crystal 3;

[0065] S2: The multi-layer crystal 3 absorbs the pump light, causing population inversion and stimulated emission of radiation, generating laser light. At the same time, combined with the crystal cutting angle, the laser light is totally reflected inside the crystal, and oscillates stably in a zigzag pattern in the resonant cavity composed of the corner cube prism 4 and the output mirror 5.

[0066] S3: The high thermal conductivity and thermal diffusivity of the diamond film in the multi-layer crystal 3 quickly conducts the heat deposited in the gain medium due to incomplete pump absorption, quantum defects, non-radiative transitions, and stimulated scattering to the cooling device 6 and removes it in time, effectively suppressing the formation of longitudinal temperature gradients. At the same time, the surface roughening eliminates spontaneous radiation oscillations, thereby significantly improving the output beam quality and the operational stability of the laser system;

[0067] S4: Using corner cube prism 4 as the resonant cavity mirror and taking advantage of its special reflection characteristics to automatically compensate for some angular errors can effectively reduce energy loss caused by slight detuning of the cavity mirror. This structure can enhance intra-cavity mode matching, optimize light field distribution, and improve light field unevenness caused by non-uniform gain or thermal effects, thereby suppressing mode competition and significantly improving the stability and beam quality of the output light beam.

[0068] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A laser with high-power pump beam quality enhancement based on multi-layer heat transfer, characterized in that: It includes a pump module (1), a pump shaping coupling module (2), a multi-layer crystal (3), a corner cube prism (4), an output mirror (5), and a cooling device (6); The pump module (1) generates pumping light to excite the multi-layer crystal (3), provides stable energy, and achieves population inversion of the crystal, and is located directly above the multi-layer crystal (3); The pump shaping coupling module (2) is located between the light outlet of the pump module (1) and the multi-layer crystal (3), and the pump light is shaped by the pump shaping coupling module (2) and then injected into the multi-layer crystal (3); The multi-layer crystal (3) is formed by stacking crystal material and diamond film. The laser incident surface of the multi-layer crystal (3) is a crystal material with a roughened surface to avoid parasitic oscillation. The interior of the crystal is a diamond film. The end face of the multi-layer crystal (3) is coated with a laser anti-reflection film, and the remaining surfaces are coated with a diamond film to facilitate and quickly remove the heat of the crystal. The oscillating laser propagates in a zigzag shape through total internal reflection inside the multi-layer crystal (3), so that the uneven thermal effects of the laser in different areas in the y direction offset each other, thereby achieving the purpose of weakening or even eliminating the thermal lens effect. The corner cube prism (4) is placed on the left side of the multi-layer crystal (3), with its center on the same horizontal line as the center of the multi-layer crystal (3) and arranged in a vertical direction, that is, its main axis is perpendicular to the horizontal line. The corner cube prism (4) not only ensures the consistency of light beam propagation through light path folding and light beam homogenization, but also significantly improves the energy distribution uniformity under high-power pumping, which helps to improve the light beam quality and operation stability of the laser output; The output mirror (5) is placed on the left side of the multi-layer crystal (3), with its center on the same horizontal line as the center of the multi-layer crystal (3) and parallel to the corner cube prism (4), forming a resonant cavity; The cooling device (6) is located below the multi-layer crystal (3) and is intended to dissipate heat efficiently and ensure that the crystal maintains a stable temperature distribution during operation.

2. The laser for achieving high-power pump beam quality enhancement based on multi-layer heat transfer according to claim 1, characterized in that: The pump module (1) is used to provide pump energy to the laser gain medium, and the pump module (1) is a semiconductor laser diode LD or a flash lamp pump module or a fiber-coupled pump module.

3. The laser for achieving high-power pump beam quality enhancement based on multi-layer heat transfer according to claim 1, characterized in that: The multi-layer crystal (3) serves as a laser gain medium, can effectively absorb pump light and achieve population inversion to generate laser output, and the gain layer is doped with rare earth elements, and the gain layer is a solid laser crystal of Nd³⁺, Yb³⁺, and Er³⁺ to provide high-efficiency laser gain.

4. The laser for achieving high-power pump beam quality enhancement based on multi-layer heat transfer according to claim 3, characterized in that: The solid laser crystals of Nd³⁺, Yb³⁺, and Er³⁺ are solid laser crystals of Nd:YAG, Yb:YAG, and Er:YAG.

5. The laser for achieving high-power pump beam quality enhancement based on multi-layer heat transfer according to claim 1, characterized in that: The cooling device (6) is a water-cooling heat dissipation device, a static gas conduction cooling device, a flowing air-water mixed cooling device, or a semiconductor cooler TEC cooling device.

6. The laser for achieving high-power pump beam quality enhancement based on multi-layer heat transfer according to claim 1, characterized in that: By combining the corner cube prism (4) with the multi-layer crystal (3), the light beam is propagated in a uniform zigzag path in the resonant cavity, which not only improves the beam shaping and uniformity, but also significantly suppresses the wavefront distortion caused by heat. The corner cube prism (4) can compensate for the cavity mirror installation error and improve the mode matching in the cavity. In combination with the transverse heat diffusion structure of the multi-layer crystal (3), the problem of beam quality degradation caused by the longitudinal temperature gradient is effectively eliminated, thereby obtaining a high-stability, high-quality output laser.

7. The method for applying a laser to achieve high-power pump beam quality enhancement based on multi-layer heat transfer according to any one of claims 1 to 6, characterized in that: include: S1: The pump module (1) emits pump light, which is uniformly shaped by the pump shaping coupling module (2) and then pumps the multi-layer crystal (3); S2: The multi-layer crystal (3) absorbs the pump light to form a population inversion, which causes stimulated radiation to generate laser light. At the same time, combined with the crystal cutting angle, the laser light is totally reflected inside the crystal and oscillates stably in a zigzag pattern in the resonant cavity composed of the corner cube prism (4) and the output mirror (5); S3: The high thermal conductivity and thermal diffusivity of the diamond film in the multi-layer crystal (3) quickly transfer the heat deposited in the gain medium due to incomplete pump absorption, quantum loss, non-radiative transition, and stimulated scattering to the cooling device (6) and remove it in time, effectively suppressing the formation of longitudinal temperature gradients. At the same time, the surface roughening eliminates spontaneous radiation oscillations, thereby significantly improving the output beam quality and the operational stability of the laser system; S4: Using the corner cube prism (4) as the cavity mirror of the resonant cavity and utilizing the special reflection characteristics of the corner cube prism (4) to automatically compensate for part of the angle error can effectively reduce the energy loss caused by the slight detuning of the cavity mirror. This structure can enhance the mode matching in the cavity, optimize the light field distribution, and improve the light field unevenness caused by gain non-uniformity or thermal effect, thereby suppressing mode competition and significantly improving the stability and beam quality of the output light beam.

Images