Thermal stress self-matching laser device and regulation and control method thereof

Abstract

The invention relates to the technical field of all-solid-state laser, and provides a thermal stress self-matching laser device and a regulation and control method thereof. The resonant cavity oscillates the pumping laser, and an input lens and an output lens are oppositely arranged in the resonant cavity; the gain medium is arranged between the input lens and the output lens; the stress self-adaptive heat sink is used for dissipating heat and can monitor and adjust a real-time stress value borne by the gain medium; the power meter is arranged at the downstream of the output lens along the light path and is used for measuring the power of the output laser; a stress threshold value is preset in the processor; and the processor is used for controlling the stress adaptive heat sink to adjust the real-time stress value based on the power and the stress threshold value, so that the power meets a preset requirement. According to the invention, the stress of the gain medium in the operation process of the laser is monitored, regulated and controlled, and the stress matching of the gain medium is realized, so that the thermally induced stress damage risk of the gain medium is reduced.

Description

Technical Field

[0001] The present invention relates to the field of all-solid-state laser technology, and in particular to a thermal stress self-matching laser device and a control method thereof. Background Art

[0002] With the continuous development of laser technology, high-power laser technology has been widely applied in many fields. In the field of laser processing, high-power lasers can achieve rapid cutting and precision welding of metals, significantly improving processing efficiency and quality. They are widely used in industries such as automotive manufacturing and mechanical processing. In the medical field, high-power lasers are used to perform high-precision surgical procedures such as laser cutting and ablation, which can effectively reduce damage to surrounding tissues and shorten patients' postoperative recovery time. In addition, in the field of scientific research, high-power lasers are powerful tools for exploring extreme physical conditions and conducting cutting-edge scientific research. They can be used to generate ultrafast light pulses and simulate high-temperature and high-pressure environments.

[0003] In the prior art, in order to achieve high-power output and ensure stable operation of the laser system, various methods are commonly used to reduce thermally induced stress damage to the gain medium caused by high power. For example, optimizing the laser cavity design, improving the cooling system, and using high-performance heat sink materials can effectively reduce the generation of thermally induced stress. Among them, optimizing the heat sink structure is an efficient and commonly used solution. By increasing the heat sink area and improving the heat conduction efficiency, it can significantly reduce the temperature of the crystal during high-power operation. However, this results in a large and complex device structure. Moreover, since the crystal is confined in the heat sink, its expansion after heating can easily cause crystal damage.

[0004] Therefore, how to reduce thermally induced stress damage in nonlinear crystals is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] The present invention provides a thermal stress self-matching laser device and a control method thereof, which are used to solve the defect in the prior art that the expansion of the crystal after being heated can easily lead to crystal damage. The device monitors and controls the stress of the gain medium during the operation of the laser, achieves stress matching of the gain medium, and thus reduces the risk of thermally induced stress damage to the gain medium.

[0006] The present invention provides a thermal stress self-matching laser device, comprising: A pump light source, used to provide pump laser for the operation of the laser oscillator; a resonant cavity, arranged in the light-emitting direction of the pump laser, for oscillating the pump laser; an input lens and an output lens are arranged opposite to each other in the resonant cavity; A gain medium is provided between the input lens and the output lens, and is used to receive the pump laser and perform nonlinear frequency conversion to generate output laser; A stress-adaptive heat sink clamps the gain medium, and the stress-adaptive heat sink is used to dissipate heat and can monitor and adjust the real-time stress value borne by the gain medium; a power meter, disposed downstream of the output lens along the optical path, the power meter being used to measure the power of the output laser; A processor has an internal preset stress threshold; the processor is used to control the stress adaptive heat sink to adjust the real-time stress value based on the power and the stress threshold so that the power meets the preset requirement.

[0007] According to a thermal stress self-matching laser device provided by the present invention, the stress adaptive heat sink comprises: At least two heat dissipation blocks are movably clamped on the periphery of the gain medium to adjust the stress value applied to the gain medium; At least one stress monitoring plate, wherein the stress monitoring plate is used to monitor the stress value applied by the heat sink to the gain medium.

[0008] According to a thermal stress self-matching laser device provided by the present invention, the stress adaptive heat sink further includes: A stress adjustment component is used to adjust the stress applied by the heat sink to the gain medium.

[0009] According to a thermal stress self-matching laser device provided by the present invention, the stress monitoring plate is arranged between the heat sink and the gain medium, or the stress monitoring plate is arranged between the stress adjustment component and the heat sink, or the stress monitoring plate is arranged between two adjacent heat sinks.

[0010] According to a thermal stress self-matching laser device provided by the present invention, the heat sink block is provided with a mounting groove, and the stress adjustment component includes: Electric control nut; The elastic member is sleeved on the outer periphery of the electric control nut, and the elastic member is arranged in the installation groove.

[0011] According to a thermal stress self-matching laser device provided by the present invention, the heat dissipation block includes at least two composite material layers with different thermal expansion coefficients, and the thermal expansion coefficients of the composite material layers are arranged to increase from the inside to the outside.

[0012] A thermal stress self-matching laser device provided by the present invention further includes: The stress monitoring module is used to convert the displacement of the stress adaptive heat sink into a stress signal.

[0013] According to a thermal stress self-matching laser device provided by the present invention, an elastic protective sheet is provided between the stress adaptive heat sink and the gain medium.

[0014] According to a thermal stress self-matching laser device provided by the present invention, the inner contour of the stress adaptive heat sink matches the outer peripheral shape of the gain medium.

[0015] The present invention also provides a control method for a thermal stress self-matching laser device, comprising: Setting stress thresholds within the processor; The stress-adaptive heat sink monitors the real-time stress value of the gain medium; the power meter monitors the power value of the output laser; The processor compares the real-time stress value with the stress threshold to form a comparison result; According to the comparison result, the processor controls the stress adaptive heat sink to adjust the stress value applied to the gain medium until the power value reaches a preset range.

[0016] The thermal stress self-matching laser device and control method provided by the present invention provide pump laser for operation of a laser oscillator through a pump light source, a resonant cavity vibrates the pump laser, a gain medium is arranged between an input lens and an output lens, the gain medium receives the pump laser and performs nonlinear frequency conversion to generate output laser; a stress-adaptive heat sink clamps the gain medium, a power meter measures the power of the output laser, a stress threshold is preset inside a processor, and based on the power of the output laser and the stress threshold, the stress-adaptive heat sink is controlled to adjust the real-time stress value borne by the gain medium so that the power meets the preset requirement, thereby realizing monitoring and control of the gain medium stress during operation of the laser, achieving stress matching of the gain medium, and reducing the risk of thermally induced stress damage to the gain medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of the optical path of a thermal stress self-matching laser device provided by an embodiment of the present invention; Figure 2 1 is a schematic structural diagram of a stress-adaptive heat sink provided by an embodiment of the present invention; Figure 3 is a schematic structural diagram of another stress-adaptive heat sink provided by an embodiment of the present invention; Figure 4 is a structural schematic diagram of another stress adaptive heat sink provided by an embodiment of the present invention; Figure 5 This is a flow chart of a control method for a thermal stress self-matching laser device provided by an embodiment of the present invention.

[0019] Reference numerals: 1. Pump light source; 2. Shaping module; 3. Resonant cavity; 31. Input lens; 32. Output lens; 4. Gain medium; 5. Stress adaptive heat sink; 51. Heat sink; 52. Stress monitoring sheet; 53. Stress adjustment component; 531. Electric control nut; 532. Elastic part; 6. Power meter; 7. Processor; 8. Stress monitoring module; 9. Elastic protection sheet. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0021] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0022] The following combination Figures 1-4 The thermal stress self-matching laser device of the present invention includes a pump light source 1, a resonant cavity 3, a gain medium 4, a stress adaptive heat sink 5, a power meter 6 and a processor 7.

[0023] like Figure 1 As shown, the pump light source 1 is used to provide pump laser for the operation of the laser oscillator. The pump light source 1 can be an ultrashort pulse laser or a continuous laser. The present invention does not limit the type of the pump light source.

[0024] The resonant cavity 3 is arranged in the direction of the pump laser emission and includes an input lens 31 and an output lens 32 arranged opposite to each other, for oscillating the pump laser.

[0025] The gain medium 4 is disposed in the resonant cavity 3 and located between the input lens 31 and the output lens 32 , and is used to receive the pump laser and perform nonlinear frequency conversion to generate output laser.

[0026] The stress-adaptive heat sink 5 is disposed between the input lens 31 and the output lens 32. The gain medium 4 is located within the stress-adaptive heat sink 5, which holds the gain medium 4. The stress-adaptive heat sink 5 is used to dissipate heat and monitor and adjust the real-time stress applied to the gain medium 4. This application does not limit the method of applying stress; for example, stress can be applied via a diamond anvil or other fasteners.

[0027] The power meter 6 is located after the output lens 32 along the optical path and is used to measure the power of the output laser.

[0028] A stress threshold is preset within the processor 7. It will be appreciated that the stress that the gain medium 4 can withstand has been measured in advance and stored in the processor 7 as the stress threshold. The processor 7 is configured to receive the stress value of the gain medium 4 monitored by the stress-adaptive heat sink 5 and the power monitored by the power meter 6. Based on the power and the stress threshold stored within the processor, the processor controls the stress-adaptive heat sink 5 to adjust the stress value applied to the gain medium 4, ensuring that it remains below the stress threshold to protect the gain medium 4. This reduces the risk of thermally induced stress damage to the gain medium, achieves stress matching of the gain medium 4, and ensures that the output laser power meets preset magnitude and stability requirements.

[0029] It should be noted that in laser devices, stress changes in the gain medium 4 are affected by multiple factors, typically thermal effects, optical field effects, and mechanical constraints. In the above embodiment, the stress-adaptive heat sink 5 monitors the stress of the gain medium under various factors. However, the stress-adaptive heat sink 5 adjusts the stress caused by the mechanical constraints of the gain medium 4, specifically the stress value of the gain medium 4 under the mechanical constraints imposed by the stress-adaptive heat sink 5, thereby achieving real-time stress changes in the gain medium 4.

[0030] like Figure 2-4 As shown, in some embodiments of the present invention, the stress adaptive heat sink 5 includes at least two heat dissipation blocks 51 and one or more stress monitoring plates 52. Each of the heat dissipation blocks 51 is movably arranged to adjust the stress value applied to the gain medium 4; the stress monitoring plate 52 is used to monitor the stress value applied to the gain medium 4 by the heat dissipation block 51. The present invention does not limit the method of applying stress. For example, stress can be applied by a diamond anvil or by other fasteners.

[0031] It will be appreciated that in the above embodiments, stress monitoring sheet 52 typically monitors the local stress value experienced by gain medium 4, and heat sink 51 regulates the local mechanical stress value applied to gain medium 4, thereby causing a change in the real-time stress value of gain medium 4. The provision of multiple stress detection sheets 52 allows for monitoring the local stress values ​​experienced at different locations on gain medium 4, enabling targeted adjustments.

[0032] In the thermal stress self-matching laser device of the above embodiment, a stress-adaptive heat sink 5 is provided, and the gain medium 4 is disposed within at least two heat sinks 51. A stress monitoring plate 52 is provided to monitor the stress value of the gain medium 4 in one or more directions. By adjusting the position of the heat sink 51, the stress applied to the gain medium 4 can be changed and monitored in real time. At the same time, the power of the output laser is monitored in real time by a power meter 6, so that a high and stable power output is achieved within the stress threshold range while achieving a good cooling effect.

[0033] See again Figure 2-4 As shown, the stress adaptive heat sink 5 further includes a stress adjustment component 53 , which is used to adjust the stress applied by the heat dissipation block 51 to the gain medium 4 .

[0034] In some embodiments, see Figure 2 As shown, the stress monitoring piece 52 is arranged between the heat sink 51 and the gain medium 4. In this embodiment, stress can be applied to the heat sink 51 through the stress adjustment component 53, and the stress acts on the gain medium 4 through the stress monitoring piece 52.

[0035] In other embodiments, see Figure 3 As shown, the stress monitoring piece 52 is arranged between the stress adjustment component 53 and the heat sink 51. In this embodiment, stress can be applied to the stress monitoring piece 52 through the stress adjustment component 53, and the stress acts on the gain medium 4 through the heat sink 51.

[0036] In yet another embodiment, see Figure 4 As shown, the stress monitoring piece 52 is arranged between two adjacent heat dissipation blocks 51 , and after stress is applied to the two adjacent heat dissipation blocks 51 through the stress adjustment component 53 , the stress acts on the gain medium 4 .

[0037] See again Figure 3 and Figure 4 As shown, in some embodiments, the stress adjustment component 53 can also be used to connect two adjacent heat dissipation blocks 51 to make the overall enclosed structure more stable.

[0038] like Figure 3As shown, in some feasible embodiments of the present invention, a mounting slot is provided on the heat sink 51, and the stress adjustment assembly 53 includes an electric control nut 531 and an elastic member 532. The elastic member 532 is sleeved around the outer periphery of the electric control nut 531 and is disposed within the mounting slot to ensure stable installation of the elastic member 532. By adjusting the electric control nut 531, the stress applied by the heat sink 51 to the gain medium can be adjusted.

[0039] Some feasible embodiments of the present invention further include a shaping module 2, disposed between the pump light source 1 and the resonant cavity 3. Shaping module 2 is disposed in the optical path of the pump laser and is used to shape the pump light. Shaping module 2 may include a combination of convex lenses, concave lenses, and the specific structure of shaping module 2 is not limited by the present invention.

[0040] In some feasible embodiments of the present invention, a stress monitoring module 8 is further included, which is used to convert the deformation of the gain medium 4 into a stress signal, and further obtain the stress value of the gain medium 4.

[0041] It should be noted that in the above embodiment, the stress monitoring module 8 measures the stress value of the gain medium 4 as a whole. When subjected to stress, the gain medium 4 experiences birefringence, which affects the polarization state of light, resulting in a phase difference between the probe light and the detection light. These phase differences form interference fringes after passing through the analyzer. The stress distribution within the medium can be analyzed and calculated based on the density and direction of the interference fringes. The density of the interference fringes reflects the magnitude of the stress, while the direction of the fringes reflects the direction of the stress.

[0042] See again as 2- Figure 4 As shown, in some feasible embodiments of the present invention, an elastic protective sheet 9 is provided between the stress-adaptive heat sink 5 and the gain medium 4, and the elastic protective sheet 9 can protect the gain medium 4. In different embodiments, the elastic protective sheet 9 is provided between the gain medium 4 and the heat sink 51, or between the gain medium 4 and the stress monitoring sheet 52.

[0043] In some embodiments, the inner profile of the stress-adaptive heat sink 5 matches the outer shape of the gain medium 4. For example, if the gain medium 4 is a rectangular parallelepiped, the inner cross-section of the stress-adaptive heat sink 5 should be rectangular to enclose the gain medium 4 and enhance cooling. The present invention does not limit the number of heat sinks 51; for example, two or three heat sinks may be provided.

[0044] In some embodiments, the material of the stress monitoring piece 52 includes at least one of piezoelectric ceramic (PZT), zinc oxide, and aluminum nitride.

[0045] In the above embodiment, the heat sink 51 and the stress monitoring plate 52 can correspond one to one or one to many. To ensure accurate and convenient monitoring, one stress monitoring plate 52 can be provided for each heat sink 51. Preferably, stress monitoring plates 52 and heat sinks 51 can be provided in different directions of the gain medium 4. If the gain medium 4 is a regular polygon, a stress monitoring plate 52 and a heat sink 51 can be provided on each face to facilitate monitoring of stress in each direction and to adjust the stress applied to the heat sink 51 in that direction accordingly.

[0046] In the above embodiment, the heat sink 51 comprises at least two composite material layers (not shown) with different thermal expansion coefficients. The thermal expansion coefficients of the composite material layers are arranged to increase from the inside out. Dynamic matching of the thermal expansion coefficient with the gain medium 4 is achieved through a gradient design of the material composition. The heat sink 5 can be constructed of a gradient composite material composed of a metal matrix (e.g., copper) and ceramic particles (e.g., silicon carbide). The ceramic particle content gradually increases from the side closest to the gain medium toward the side away from the gain medium. This results in a gradient variation in the thermal expansion coefficient of the heat sink 51 from the inside out, dynamically compensating for the thermal expansion behavior of the gain medium 4 and reducing stress mismatch caused by temperature changes. The stress monitoring sheet 52 provides real-time feedback on the stress distribution in different regions of the gain medium 4. By combining the thermal-mechanical coupling properties of the gradient material, the stress adjustment component 53 applies differentiated pressure to the local heat sink, achieving precise compensation for uneven thermal stress.

[0047] The thermal stress self-matching laser device provided by the present invention uses a pump laser shaped by a shaping module 2 and then injected into a stress-adaptive heat sink 5. Mid-infrared laser light is generated through nonlinear frequency conversion and output through an output lens. This compact device automatically monitors and adjusts heat sink stress, addressing the issue of thermally induced stress damage to the gain medium in current mid-infrared pulsed laser heat sinks.

[0048] See also Figure 5 As shown, the present invention also provides a control method for a thermal stress self-matching laser device, which is used for a thermal stress self-matching laser device. The control method includes: S100: Setting a stress threshold in the processor.

[0049] S200 , the stress adaptive heat sink 5 monitors the real-time stress value borne by the gain medium 4 ; the power meter 6 detects the power value of the output laser.

[0050] S300 : The processor 7 compares the real-time stress value with the stress threshold to form a comparison result.

[0051] S400 , based on the comparison result, the processor 7 controls the stress adaptive heat sink 5 to adjust the stress value applied to the gain medium 4 until the power value reaches a preset range.

[0052] The control method of the thermal stress self-matching laser device of the present invention monitors the stress value of the gain medium 4 in one or more directions in real time through the stress adaptive heat sink 5 and then adjusts the position of the stress adaptive heat sink 5 to change and monitor the stress applied to the gain medium 4 in real time. At the same time, the power of the output laser is monitored in real time through the power meter 6, so that a good cooling effect is achieved within the stress threshold range while meeting the preset stress range and stable power output.

[0053] In some optional embodiments, in step S400, the stress value applied to the gain medium 4 by the heat sink 51 is monitored by the stress monitoring piece 52 in the stress adaptive heat sink 5, the monitored stress value is compared with the stress threshold, and the positions of different heat sinks 51 are adjusted respectively to adjust the stress values ​​applied to different positions of the gain medium 4, so that all stress values ​​are less than the stress threshold until the power value reaches a preset range and reaches a stable state.

[0054] In the above embodiment, by adjusting the positions of the plurality of heat dissipation blocks 51 , the stress of the gain medium 4 can be locally adjusted to achieve more precise control.

[0055] In the description of the embodiments of the present invention, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "mode", "specific mode", or "some modes" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or mode are included in at least one embodiment or mode of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or mode. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or modes in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or modes and features of different embodiments or modes described in this specification without contradiction.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A thermal stress self-matching laser device, characterized in that: include: A pump light source (1) for providing pump laser light for the operation of the laser oscillator; A resonant cavity (3) is arranged in the light-emitting direction of the pump laser and is used to oscillate the pump laser; an input lens (31) and an output lens (32) are arranged opposite to each other in the resonant cavity (3); A gain medium (4) is provided between the input lens (31) and the output lens (32), and the gain medium (4) is used to receive the pump laser and perform nonlinear frequency conversion to generate output laser light; A stress-adaptive heat sink (5) clamps the gain medium (4), and the stress-adaptive heat sink (5) is used to dissipate heat and can monitor and adjust the real-time stress value borne by the gain medium (4); a power meter (6), arranged downstream of the output lens (32) along the optical path, the power meter (6) being used to measure the power of the output laser; A processor (7) has an internally preset stress threshold; the processor (7) is used to control the stress adaptive heat sink (5) to adjust the real-time stress value based on the power and the stress threshold so that the power meets the preset requirement.

2. The thermal stress self-matching laser device according to claim 1, characterized in that: The stress adaptive heat sink (5) comprises: At least two heat dissipation blocks (51) are movably clamped on the periphery of the gain medium (4) to adjust the stress value applied to the gain medium (4); At least one stress monitoring plate (52), the stress monitoring plate (52) being used to monitor the stress value applied by the heat dissipation block (51) to the gain medium (4).

3. The thermal stress self-matching laser device according to claim 2, characterized in that: The stress adaptive heat sink (5) further comprises: A stress adjustment component (53) is used to adjust the stress applied by the heat dissipation block (51) to the gain medium (4).

4. The thermal stress self-matching laser device according to claim 3, characterized in that: The stress monitoring piece (52) is arranged between the heat dissipation block (51) and the gain medium (4), or the stress monitoring piece (52) is arranged between the stress adjustment component (53) and the heat dissipation block (51), or the stress monitoring piece (52) is arranged between two adjacent heat dissipation blocks (51).

5. The thermal stress self-matching laser device according to claim 3, characterized in that: The heat dissipation block (51) is provided with a mounting slot, and the stress adjustment component (53) comprises: Electric control nut (531); The elastic member (532) is sleeved on the outer periphery of the electric control nut (531), and the elastic member (532) is arranged in the installation groove.

6. The thermal stress self-matching laser device according to any one of claims 1 to 5, characterized in that: The heat dissipation block (51) comprises at least two composite material layers with different thermal expansion coefficients, and the thermal expansion coefficients of the composite material layers are arranged to increase from the inside to the outside.

7. The thermal stress self-matching laser device according to claim 6, characterized in that: Also includes: A stress monitoring module (8) is used for converting the deformation of the gain medium (4) into a stress signal.

8. The thermal stress self-matching laser device according to claim 6, characterized in that: An elastic protection sheet (9) is provided between the stress-adaptive heat sink (5) and the gain medium (4).

9. The thermal stress self-matching laser device according to claim 6, characterized in that: The inner contour of the stress adaptive heat sink (5) matches the outer peripheral shape of the gain medium (4).

10. A control method for a thermal stress self-matching laser device, used for the thermal stress self-matching laser device according to any one of claims 1 to 9, characterized in that: Setting a stress threshold in the processor (7); The stress adaptive heat sink (5) monitors the real-time stress value of the gain medium (4); the power meter (6) monitors the power value of the output laser; The processor (7) compares the real-time stress value with the stress threshold to form a comparison result; According to the comparison result, the processor (7) controls the stress adaptive heat sink (5) to adjust the stress value applied to the gain medium (4) until the power value reaches a preset range.

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