A fiber laser

Abstract

This invention discloses a fiber laser, comprising a cylindrical housing, a heating element, an internal fan, and an external cooling assembly. The cylindrical housing is made of a thermally conductive material, with end caps at both ends sealed to the side walls to form a closed cavity. The heating element, including the pump source and fiber optic assembly, is installed within the closed cavity and is in thermal contact with the inner wall of the housing and / or the end caps. The internal fan is fixed to the inside of the end caps, driving the gas circulation within the cavity and transferring heat to the inner surfaces of the side walls and the end caps. The external cooling assembly is mounted on the outer surface of the side walls and includes heat dissipation fins and a detachable forced convection device. The forced convection device can be interchangeably configured as an air-cooled fan or a liquid-cooled forced flow component depending on the type of cooling medium. This invention achieves coordinated internal and external thermal management by constructing a short heat transfer path for internal heating and external cooling, combined with internal forced convection and active heat dissipation using an externally adapted cooling medium, significantly improving heat dissipation efficiency and internal temperature uniformity.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, specifically relating to a fiber laser, which is mainly used in industrial processing, scientific research, medical and defense applications that require high-power laser output and have strict requirements for operating temperature stability. Background Technology

[0002] Fiber lasers, as efficient and compact solid-state laser sources, are widely used in industrial processing, medical applications, scientific research, and national defense. With the continuous increase in output power, factors such as electro-optical conversion losses in the pump source and quantum defects in the gain fiber lead to a significant accumulation of waste heat inside the laser. If this heat cannot be effectively conducted to the external environment in a timely manner, the laser's operating temperature will continue to rise, resulting in laser wavelength drift, beam quality degradation, and decreased electro-optical conversion efficiency. In severe cases, it can even cause irreversible damage to optical components.

[0003] Traditional fiber lasers typically employ unidirectional external cooling structures for heat dissipation, such as directly mounting air-cooled radiators or liquid-cooled plates on the outside of the laser housing. Heat generated by the heat-generating components must pass through multiple interfaces—the internal air layer, the housing wall thickness, and the external radiator—before being transferred to the cooling medium. This approach results in a long heat transfer path, and the accumulated thermal resistance at each interface leads to a high overall thermal resistance, limiting cooling efficiency. For enclosed lasers, the internal air is either in a state of natural convection or stagnation, easily causing localized high-temperature hotspots near the pump source and gain fiber, while the housing and end-face areas far from the heat source remain cooler. This highly uneven temperature distribution severely affects the thermal stability of optical components.

[0004] The prominent challenges facing existing technologies are: how to effectively shorten the heat transfer path between the core heat-generating components and the external cooling medium to reduce the overall thermal resistance of the system; how to break the thermal stratification inside the enclosed cavity to achieve uniform temperature distribution; and how to enable the same laser structure to flexibly adapt to different operating environments such as air cooling and liquid immersion cooling without major modifications. Currently, the market lacks a thermal management solution for fiber lasers that can simultaneously achieve short heat transfer paths, internal temperature uniformity, multi-medium adaptability, and structural compactness. This, to some extent, limits the widespread application of high-power fiber lasers under complex deployment conditions, becoming a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a fiber laser that solves the problems of long heat transfer paths, local hot spots caused by internal heat accumulation, and the difficulty of a single cooling structure to flexibly adapt to two different cooling media, air and liquid, in existing laser heat dissipation technologies.

[0006] To address the above problems, the present invention provides a fiber laser, comprising: The cylindrical shell structure is made of thermally conductive material and has cylindrical sidewalls and end caps at both ends. The end caps are sealed to the sidewalls to form a closed cavity. A heating element is installed in a closed cavity and is in thermal contact with the inner surface of the side wall and / or the inner surface of the end cap. The heating element includes a pump source and an optical fiber assembly. An internal fan, fixed to the inside of at least one end cover, has its rotation axis parallel or coincident with the central axis of the housing. It is used to agitate the gas in the closed cavity and force the gas to flow axially and diffuse radially at the end cover to form a circulating airflow, which transfers the heat generated by the heating element to the inner surface of the side wall and the inner surface of the two end covers. An external cooling assembly is mounted on the outer surface of a sidewall and includes multiple heat dissipation fins arranged along the outer surface of the sidewall, as well as a detachably mounted forced convection device for forcing the cooling medium to flow through the heat dissipation fins. When the fiber laser is working, it is placed entirely in the cooling medium. The forced convection device is selectively either an air-cooled fan or a liquid-cooled forced flow component, depending on the type of cooling medium, to achieve active and passive heat dissipation in coordination with the external environment and to improve the internal temperature uniformity.

[0007] Furthermore, at least one heat pipe or a vapor chamber is embedded in the sidewall of the cylindrical shell. The first end of the heat pipe or vapor chamber is close to the inner surface of the sidewall and in contact with the internal circulating gas, and the second end extends to the outer surface of the sidewall and is thermally connected to the heat dissipation fins, so as to provide a low thermal resistance heat conduction path based on phase change heat transfer through the sidewall.

[0008] Furthermore, a micro flow regulating valve that can be independently addressed and controlled is installed on the liquid supply line of the liquid jet nozzle array. At the same time, multiple temperature sensors are arranged at different positions along the axial direction on the outer surface of the side wall or in the closed cavity. The fiber laser also includes a controller, which is configured to independently adjust the opening degree or pulse frequency of the micro flow regulating valve at the corresponding position according to the axial temperature difference distribution fed back by multiple temperature sensors, so as to implement differentiated enhanced jet cooling for local high temperature areas.

[0009] Furthermore, an airflow distributor is fixedly installed inside the enclosed cavity, near the air outlet of the internal fan. A set of guiding nozzles is provided on the airflow distributor, and the outlet of the guiding nozzles faces the surface of the pump source or optical fiber assembly, so as to convert part of the axial airflow driven by the internal fan into multiple local jets that directly impact the heating component.

[0010] Furthermore, a thermoelectric cooler is attached to the inner or outer surface of at least one end cap of the cylindrical housing. The cold end of the thermoelectric cooler is in thermal contact with the gas inside the end cap or the enclosed cavity, and the hot end is in thermal connection with an external cooling component or directly exposed to an external cooling medium. The thermoelectric cooler is configured to activate when the internal temperature exceeds a preset threshold to provide active cooling.

[0011] Furthermore, the two sets of internal fans are powered independently and are located on the inner sides of both ends of the cylindrical structure housing. A flow guide structure is provided between the two sets of internal fans to ensure that the other fan can maintain the basic circulating airflow in the closed cavity when one fan fails. In addition, an emergency pressure relief and heat exhaust hole is provided on at least one end cover. The heat exhaust hole is sealed by a fusible sealing film. When the internal temperature exceeds the preset dangerous critical temperature, the sealing film melts and ruptures to release the internal heat and pressure.

[0012] The present invention has the following beneficial effects: (1) This invention directly installs the heating element inside the cylindrical shell, with only one shell wall thickness separating it from the external cooling medium, thus creating a short heat transfer path pattern of internal heating and external cooling, reducing thermal resistance. At the same time, the external heat dissipation fins, in conjunction with a forced convection device, are adapted to the type of cooling medium by using an air-cooled fan or a liquid jet nozzle array to quickly remove the heat transferred to the shell surface through active forced convection, overcoming the problem of low heat exchange efficiency in traditional methods that rely solely on natural convection or a single cooling method.

[0013] (2) The present invention sets an internal fan inside the closed cavity to drive the gas inside the cavity to form a forced circulating airflow, which breaks the phenomenon of local heat accumulation caused by poor air circulation inside the traditional closed laser. The circulating airflow absorbs heat by flowing over the surface of the heat-generating component, and then transfers the heat to the inner surface of the side wall and the inner surface of the end caps at both ends, so that the end caps at both ends are also included in the effective heat dissipation path, solving the technical problem of poor heat dissipation at the end face in the traditional design.

[0014] (3) The present invention employs a detachable forced convection device in the external cooling assembly, enabling the same laser to flexibly adapt to both air-cooled and liquid-cooled operating modes without modifying its internal core structure. Combined with the modular cooling kit design, users can quickly replace the external cooling module in different usage scenarios, improving the product's deployment convenience and maintenance efficiency. At the same time, the pressure relief and heat dissipation structure provides multiple guarantees for the safe operation of the laser under extreme conditions. The overall technical solution achieves synergistic improvement in three dimensions: heat dissipation performance, environmental adaptability, and operational reliability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the overall structure of the fiber laser in an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of the fiber laser in an embodiment of the present invention; Figure 3 This is a schematic diagram of the external structure of the fiber laser of the present invention when it is in an air-cooled medium. Figure 4 This is a schematic diagram of the external structure of the fiber laser of the present invention when it is in a liquid cooling medium.

[0017] Explanation of reference numerals in the attached drawings: 1-Heat dissipation fins; 2-Cylindrical housing structure; 3-Fiber optic assembly; 4-Pump source; 5-Internal fan; 6-Air-cooled fan; 7-Liquid jet nozzle array. Detailed Implementation

[0018] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0019] To fully understand this invention, detailed steps and structures will be presented in the following description to illustrate the technical solution of this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0020] like Figures 1 to 4 In one embodiment of the fiber laser of the present invention, the fiber laser adopts an overall cylindrical structure and is placed entirely in a cooling medium during operation. The large outer surface area of ​​the cylindrical structure is utilized to create an internal and external partitioned heat dissipation configuration. The fiber laser includes a cylindrical housing 2, a heat-generating component, an internal fan 5, and an external cooling assembly.

[0021] The cylindrical shell 2 is made of aluminum, copper, or thermally conductive composite materials, with the specific material chosen based on thermal conductivity requirements, weight constraints, and cost factors. The cylindrical shell 2 has cylindrical sidewalls and end caps at both ends. The end caps are sealed to the sidewalls via welding, flange connections, or sealing ring press-fitting, forming a closed cavity isolated from the external cooling medium. The cross-section of the cylindrical shell 2 can be designed as circular, square, or rectangular to suit different equipment compartment or cabinet layouts, depending on the actual installation space and application scenario. The heat-generating components are concentrated on the inner side of the closed cavity, while the cooling components are located on the outer side of the cylindrical shell 2, thus creating an internal heat generation and external cooling pattern, shortening the heat transfer path between the heat-generating components and the external cooling medium.

[0022] The heat-generating components are installed within a sealed cavity and mainly include a pump source 4 and an optical fiber assembly 3, as well as other optical and electronic components required for the normal operation of the laser. During operation, the pump source 4 provides pump light to the optical fiber assembly 3, generating a significant amount of heat during its electro-optical conversion process. The gain fiber in the optical fiber assembly 3 also generates heat due to quantum defects and other factors during the absorption of pump light and laser amplification. During installation, the heat-generating components maintain good thermal contact with the inner surface of the side wall and / or the inner surface of the end cap of the cylindrical housing 2 using thermally conductive pads, thermally conductive adhesive, or direct bonding, ensuring efficient heat transfer to the cylindrical housing 2 through thermal conduction at the contact surfaces.

[0023] An internal fan 5 is fixed to the inside of at least one end cap, and its rotation axis is parallel to or coincides with the central axis of the cylindrical shell 2. The internal fan 5 can be an axial fan or a centrifugal fan, selected according to the internal space of the cavity and the required airflow characteristics. When the internal fan 5 is powered on, its blades rotate and agitate the gas in the closed cavity, forcing the gas to flow in the axial direction and diffuse radially outward when it reaches the end cap, and then flow back along the inner surface of the side wall, thereby forming a circulating airflow covering the entire closed cavity. The circulating airflow sweeps across the surfaces of the pump source 4 and the optical fiber assembly 3 in a forced convection manner, carrying the heat generated by the heating element away from the component body. When the heat-carrying gas flows through the inner surface of the side wall and the inner surface of the end cap, it transfers the heat to the cylindrical shell 2 through convection heat transfer. The heat is then transferred to its outer surface through thermal conduction of the shell material, and finally dissipated into the external cooling medium by the external cooling assembly. Because the internal fan 5 forces the gas circulation, it breaks the thermal stratification and local heat accumulation in the closed cavity, and avoids the formation of local high temperature hot spots near the pump source 4 or fiber optic assembly 3 due to poor internal air circulation, thereby protecting the stability and service life of the optical components.

[0024] Preferably, there are two sets of internal fans 5, each located on the inner side of one of the two end caps, with at least one internal fan 5 installed on the inner side of each end cap. The two sets of internal fans 5 work together, simultaneously driving gas from both ends to form an axial airflow throughout the entire closed cavity, ensuring sufficient airflow coverage for all areas along the axial direction of the cylindrical shell 2. The two sets of internal fans 5 are designed with independent power supplies, each connected to an independent power supply line. A flow guiding structure is provided in the cavity space between the two sets of internal fans 5 to guide the airflow direction, ensuring that even if one set of internal fans 5 stops due to a malfunction, the gas driven by the other normally functioning internal fan 5 can still flow along a preset path through the area where the pump source 4 and fiber optic assembly 3 are located, as well as most of the heat exchange surfaces of the side walls and end caps, maintaining basic circulating airflow and heat dissipation capacity within the closed cavity, and preventing overall heat dissipation failure and laser overheating damage due to a single-point fan failure.

[0025] In addition, at least one end cap is machined with an emergency pressure relief and heat dissipation hole, which is a through-hole structure on the end cap. Under normal operating conditions of the fiber laser, the heat dissipation hole is completely sealed by a fusible sealing film. The melting point of the fusible sealing film material is selected based on the laser's maximum permissible dangerous temperature; its melting point is higher than the upper limit of the laser's normal operating temperature but lower than the critical temperature that could cause permanent damage. The fusible sealing film ensures the airtightness of the sealed cavity remains unaffected when closed. When the fiber laser encounters extreme abnormal conditions, such as complete failure of external cooling components or uncontrolled internal heating power, causing the temperature inside the sealed cavity to rise continuously and exceed the preset critical temperature, the fusible sealing film melts and ruptures upon reaching its melting point. The heat dissipation hole opens, allowing the high-temperature, high-pressure gas inside the sealed cavity to directly connect with the external cooling medium. This rapidly releases the accumulated heat and pressure, slowing down the rate of heat accumulation and providing operators with time to take emergency shutdown measures, thus playing a passive safety protection role.

[0026] An external cooling assembly is mounted on the outer surface of the sidewall of the cylindrical housing 2, including multiple heat dissipation fins 1 arranged along the outer surface of the sidewall and a detachably mounted forced convection device. The heat dissipation fins 1 extend circumferentially and / or axially along the sidewall. Specifically, the heat dissipation fins 1 can be annular fins arranged radially circumferentially around the sidewall, longitudinal fins arranged parallel in the axial direction, or needle-like or staggered fin structures extending simultaneously circumferentially and axially. The heat dissipation fins 1 are directly formed to the outer surface of the sidewall through an integral molding process such as extrusion molding or casting, or fixedly connected by welding, brazing, etc., to ensure extremely low thermal resistance between the fin roots and the sidewall, allowing heat to be efficiently conducted from the sidewall to the fin surface. The forced convection device forces the external cooling medium to flow across the surface of the heat dissipation fins 1, rapidly transferring the heat transferred to the fins into the cooling medium and carrying it away through forced convection heat transfer.

[0027] The fiber laser is entirely immersed in a cooling medium during operation. The forced convection device is selectively configured based on the specific type of external cooling medium. When the fiber laser operates in an air environment, the external cooling medium is air. In this case, the forced convection device includes an air guide shroud and a fan 6. The air guide shroud is a casing structure, covering the periphery of the heat dissipation fins 1, forming an airflow channel together with the heat dissipation fins 1 and the outer surface of the sidewall. The fan 6 is installed at one end or on the side of the air guide shroud. After being powered on, it drives the ambient air to form a directional airflow along the air guide shroud, flowing evenly through the gaps between the heat dissipation fins 1. As the air flows over the fin surface, it absorbs heat and carries it away, completing the air-cooling heat dissipation cycle. The function of the air guide shroud is to constrain the airflow direction, preventing airflow from bypassing and leaking around the fins, thereby improving the effective heat exchange efficiency of the fin surface.

[0028] When the fiber laser operates immersed in a liquid cooling medium, the external cooling medium is a liquid, such as deionized water, fluorinated liquid, or ethylene glycol aqueous solution. In this case, the forced convection device includes a liquid pump and a liquid jet nozzle array 7. The liquid jet nozzle array 7 is arranged around the sidewall, i.e., multiple nozzles are spaced apart along the circumference of the outer surface of the sidewall, or arranged axially, i.e., multiple rows of nozzles are arranged along the axis of the sidewall. The liquid pump pressurizes the external liquid cooling medium and delivers it to the liquid jet nozzle array 7. Each nozzle sprays the cooling liquid in jet form onto the surface of the heat dissipation fins 1. The liquid forms forced convection on the fin surface, rapidly carrying away heat. The specific arrangement, number of nozzles, and spray angle of the liquid jet nozzle array 7 can be optimized according to the structure and heat flux density distribution of the heat dissipation fins 1 to ensure that all areas of the fins receive sufficient liquid coverage and heat exchange.

[0029] The fiber laser also includes a power supply unit, which is located inside the enclosed cavity or outside the cylindrical housing 2. The power supply unit is electrically connected to the pump source 4, internal fan 5, and forced convection cooling fan 6 or liquid pump via cables to provide the electrical components with the necessary power. The power supply unit supports two power supply modes: one is power supply via an external power interface connected to AC mains or an external DC power source; the other is power supply via a built-in rechargeable battery or a disposable battery. These two power supply modes can be used independently or as backups for each other to meet the power supply needs of different application scenarios. For example, in portable field applications, the built-in battery can provide power, while in laboratory or industrial production lines, an external power source can be used.

[0030] To further enhance heat dissipation performance under air-cooled conditions, fiber lasers may also include heat pipes. A heat pipe is a component that utilizes an internal working fluid phase change cycle to achieve efficient heat transfer. The first end of the heat pipe, the evaporation end, is directly thermally connected to the outer shell of the heat-generating components such as the pump source 4 and the fiber optic assembly 3, or to the inner surface of the side wall of the cylindrical shell 2, to directly absorb heat from the heat-generating components or the inner wall of the shell. The second end of the heat pipe, the condensation end, extends to the heat dissipation fins 1 and is thermally connected to the root of the heat dissipation fins 1 or the fin body. When the first end is heated, the working fluid inside the heat pipe evaporates and flows to the second end, where it condenses and releases latent heat. The condensed liquid working fluid then flows back to the first end through a capillary structure, and this cycle repeats, efficiently pumping heat from the heat source end to the fin end. The heat pipe provides an auxiliary heat conduction path, which is connected in parallel with the heat conduction path of the cylindrical shell 2 itself, effectively reducing the overall thermal resistance between the heat-generating components and the heat dissipation fins 1.

[0031] In one specific embodiment, a phase change material layer is attached to the inner wall and / or the inner side of the end caps of the cylindrical shell 2. The phase change material layer is specifically disposed on the inner wall surface of the enclosed cavity, located between the inner wall of the shell and the internal circulating gas, allowing the circulating gas to directly pass over the surface of the phase change material layer during flow. The phase change material layer consists of an encapsulation shell and a solid-liquid phase change material filled within the encapsulation shell. The encapsulation shell is made of a thermally conductive metal material such as aluminum or copper, and is flat and box-shaped or bag-shaped, attached and fixed to the inner wall of the shell or the inner surface of the end caps by screws, clips, or thermally conductive adhesive. The encapsulation shell is sealed and filled with a solid-liquid phase change material, which can be paraffin-based, fatty acid-based, or inorganic salt hydrate-based phase change materials. The phase change temperature range of the phase change material is set according to the thermal characteristics of the laser, specifically set to be higher than the rated operating temperature of the laser but lower than the maximum allowable operating temperature of the laser. When the laser operates in pulsed mode or experiences a sudden load change, the pump source 4 and fiber assembly 3 generate a transiently high heat flux density, causing the air temperature inside the sealed cavity to rise rapidly. As the temperature rises into the phase transition temperature range of the phase change material, the solid-liquid phase change material within the encapsulation shell begins to absorb a large amount of latent heat and transforms from a solid to a liquid state. During this phase transition, the temperature of the phase change material itself remains essentially constant or changes very gradually, effectively suppressing the rapid rise in gas temperature within the sealed cavity and eliminating any temperature spikes that would otherwise occur. When the laser switches to low-power operation or temporarily stops emitting light, the heat generated by the heating components decreases, and the temperature inside the sealed cavity gradually drops. When the temperature falls below the phase transition temperature range, the liquid phase change material begins to release its previously stored latent heat and gradually solidifies, slowing down the rate of temperature decrease. Through this cyclical process of heat absorption during the temperature rise phase and heat release during the temperature fall phase, the system's equivalent heat capacity is increased, and temperature fluctuations are smoothed out, thereby improving the stability of the laser output power and the stability of the output laser wavelength.

[0032] In one specific embodiment, a flow guiding structure is provided within the sealed cavity. This structure includes spiral flow guiding ribs arranged circumferentially along the inner wall of the cylindrical shell 2, or flow guiding baffles arranged axially. The spiral flow guiding ribs are raised ribs extending along the inner surface of the sidewall in a spiral path. Their cross-sectional shape can be rectangular or trapezoidal, and they are integrally cast or machined with the inner surface of the sidewall, or fixed to the inner surface of the sidewall as independent rib parts by welding or screws. The flow guiding baffles are flat or arc-shaped plate structures arranged axially, with one edge connected and fixed to the inner surface of the sidewall. The spiral flow guiding ribs or flow guiding baffles divide the annular or cylindrical space inside the sealed cavity into multiple interconnected airflow channels, which are arranged in an orderly manner along the circumference and axial direction of the shell. The internal fan 5 drives the gas to flow in an orderly manner along the airflow channel. The gas first flows through the area where the pump source 4 and the fiber optic assembly 3 are located, where strong convection washes away the heat generated by the heat-generating components. Then, the gas carrying heat moves along the inner wall of the cylindrical shell 2, guided by spiral guide ribs in a spiral path, or constrained by guide baffles in an axial reversal path. During the spiral or reversal movement along the inner wall, the gas continuously exchanges heat with the large-area inner wall of the cylindrical shell 2, transferring heat to the shell. Finally, the gas reaches the inner side of the end caps at both ends, uniformly washing the inner surface of the end caps and incorporating the end caps into an effective heat dissipation path, making full use of the heat dissipation area of ​​the end caps. The guide structure eliminates the large-scale eddies and airflow short-circuiting phenomena that easily occur when relying solely on the internal fan 5 for agitation, making the internal airflow organization more orderly and the temperature distribution more uniform. Based on the above-mentioned guide structure, heat spreaders can be further attached to the inner side of the end caps at both ends. The vapor chamber is a flat, highly thermally conductive element, which can be a graphite vapor chamber or a metal vapor chamber with an internal microchannel capillary structure. The vapor chamber is attached to the inner surface of the end cap using thermally conductive adhesive or screw pressing, forming a good thermal connection with the cylindrical housing 2. When circulating gas flows over the end cap, the heat carried by the gas is rapidly diffused along the planar direction to the entire end face area through the vapor chamber, preventing heat concentration in the central area of ​​the end cap and avoiding localized overheating. This ensures that the entire area of ​​the end cap participates in heat dissipation evenly, further improving the overall heat dissipation capacity and the temperature uniformity inside the sealed cavity.

[0033] In one specific embodiment, the outer surface of the cylindrical shell 2 is provided with standardized mechanical connection interfaces and thermal connection interfaces. The mechanical connection interfaces can specifically be snap-fit ​​rails, quick-lock slots, or an array of threaded holes arranged circumferentially and axially along the outer surface of the shell sidewall. The thermal connection interfaces can specifically be a precision-machined metal mounting surface with high flatness and low roughness, or a heat spreader contact surface embedded in the outer surface of the sidewall. The external cooling assembly is designed as an independent, detachable, and replaceable cooling kit. The cooling kit includes a kit housing, the inner surface of which is provided with a mating structure that matches the mechanical connection interfaces on the cylindrical shell 2. This can be a slider that mates with the snap-fit ​​rails, an elastic latch that mates with the quick-lock slots, or a bolt through-hole corresponding to the threaded holes. The cooling kit achieves a detachable and secure mechanical fixation to the cylindrical shell 2 through the mechanical connection interfaces. Simultaneously, the thermal connection interface portion on the inner surface of the kit housing is tightly fitted with the thermal connection interface on the outer surface of the cylindrical shell 2, with the microscopic gaps filled by a thermally conductive interface material to ensure low thermal resistance thermal contact. The cooling kit is pre-configured according to the type of external cooling medium. The first kit, suitable for gas cooling media, integrates heat dissipation fins 1 and a fan 6 on its housing. The fan 6 is fixed to one end or side of the housing, forming an airflow channel inside. The second kit, suitable for liquid cooling media, integrates heat dissipation fins 1 and a liquid-cooled forced flow component on its housing. The liquid-cooled forced flow component can be a liquid jet nozzle array 7 or a liquid pump, and a quick-connect liquid line connector for external liquid supply lines is integrated on the housing. When the fiber laser needs to be deployed in an air environment, the user installs the first kit onto the cylindrical housing 2 via a standard interface and locks it in place. When liquid immersion cooling is required, the user loosens and disassembles the first kit, then installs the second kit. The entire process does not require modification of the fiber laser's internal structure. The modular, quick-change design of the cooling kits allows the same fiber laser to flexibly adapt to different cooling environments, significantly improving deployment flexibility, maintenance convenience, and reducing customization costs for different customer environments.

[0034] In one specific embodiment, at least one heat pipe or a vapor chamber is embedded in the sidewall of the cylindrical shell 2. The heat pipe is a slender tubular phase change heat transfer element, and the vapor chamber is a flat plate-shaped phase change heat transfer element. Both utilize the evaporation and condensation cycle of the internal working fluid to achieve efficient heat transfer. During the processing of the sidewall of the cylindrical shell 2, blind holes or through holes matching the outer diameter of the heat pipe are pre-drilled inside the sidewall material, or a flat cavity matching the thickness of the vapor chamber is pre-reserved inside the sidewall. The heat pipe or vapor chamber is embedded into the pre-reserved holes or cavity and filled with a thermally conductive interface material to ensure tight contact. The first end of the heat pipe or vapor chamber, i.e., the heat absorption end, is located close to the inner surface of the sidewall and is in direct contact with the heated gas circulating in the closed cavity or separated only by a thin wall. The heat carried by the gas can be easily transferred to the heat absorption end of the heat pipe or vapor chamber. The second end of the heat pipe or vapor chamber, i.e., the heat dissipation end, extends along the inside of the sidewall to the outer surface of the sidewall and forms a thermal connection with the root of the heat dissipation fins 1. When the internal circulating gas transfers heat to the inner surface of the sidewall, part of the heat is conducted radially outward through the material of the cylindrical shell 2 itself, while the other part is absorbed by the embedded heat pipes or vapor chambers. The working fluid inside the heat pipes or vapor chambers evaporates at the heat absorption end and flows rapidly to the heat release end, where it condenses and releases latent heat, directly transferring the heat to the root region of the heat dissipation fins 1. This shell-embedded structure provides a low thermal resistance heat conduction path based on phase change heat transfer that runs through the sidewall, breaking the limitation that heat must rely entirely on the radial diffusion of the shell material's own heat conduction. This allows the heat carried by the internal gas to be directly pumped to the far end of the fins with extremely low thermal resistance, thereby significantly reducing the temperature difference between the inner and outer walls of the cylindrical shell 2. This makes the overall temperature distribution of the shell closer to an isothermal body, and all areas of the external heat dissipation fins 1 can be fully utilized, resulting in a significant improvement in overall heat dissipation efficiency.

[0035] In one specific embodiment, a micro flow regulating valve with independent addressability is installed on the liquid supply line of the liquid jet nozzle array 7. Each nozzle or group of nozzles in the liquid jet nozzle array 7 is equipped with a corresponding micro flow regulating valve. The micro flow regulating valve can be an electromagnetically driven or piezoelectrically driven micro valve, capable of receiving electronic control signals and continuously or progressively regulating the flow rate of coolant through the valve body. Simultaneously, multiple temperature sensors are arranged at different axial positions on the outer surface of the side wall of the cylindrical housing 2, or at different axial positions on the inner wall of the enclosed cavity. These temperature sensors are used to monitor the temperature near their respective installation positions in real time. The signal lines of all temperature sensors and the control lines of all micro flow regulating valves are connected to a controller. The controller has a preset temperature zoning control strategy. During operation, the controller collects the temperature readings of each temperature sensor in real time and calculates the temperature difference distribution data along the axial direction. When the controller detects that the temperature of a certain axial zone is significantly higher than that of other zones or exceeds the preset uniform temperature target value, the controller sends a command to the corresponding micro-flow regulating valve to increase the valve opening or increase its pulse jet frequency, thereby increasing the coolant jet flow rate in that local area and implementing stronger convective impact cooling for the heat dissipation fins 1 in that local high-temperature area. For zones where the temperature is already within the normal range or relatively low, the controller reduces the opening of the corresponding micro-flow regulating valve or decreases its pulse frequency to reduce unnecessary coolant flow and pumping power consumption. This on-demand zone-based differentiated cooling method based on real-time temperature feedback replaces the traditional global uniform flow cooling method. While ensuring the overall temperature uniformity of the laser, it reduces the energy consumption of the liquid pump, slows down the overall temperature rise of the coolant, and achieves a simultaneous improvement in the energy efficiency ratio and temperature field control accuracy of the liquid cooling system.

[0036] In one specific embodiment, an airflow distributor is fixedly installed inside the enclosed cavity, near the air outlet of the internal fan 5. The airflow distributor is a hollow shell structure, with its air inlet connected to the air outlet of the internal fan 5. All or part of the axial airflow blown out by the internal fan 5 enters the inner cavity of the airflow distributor. A set of guide nozzles is provided on the front or side wall of the airflow distributor. The guide nozzles are nozzle structures with gradually narrowing cross-sections. The outlet direction of each guide nozzle is precisely designed so that it faces the outer shell surface of the pump source 4 or the area of ​​concentrated heat in the fiber optic assembly 3. After the high-pressure axial airflow driven by the internal fan 5 enters the airflow distributor, it is gathered by the inner cavity and evenly distributed to each guide nozzle. The airflow is accelerated in the narrowing cross-section of the guide nozzle and transformed into multiple high-speed jets that are ejected from each outlet, directly impacting the surface of the pump source 4 or the fiber optic assembly 3. The high-speed jet impact can effectively thin or even destroy the thermal boundary layer on the surface of the heat-generating component, greatly increasing the convective heat transfer coefficient between the component surface and the cooling airflow, thereby forming a locally enhanced convective cooling effect on the surface of the heat-generating component. Meanwhile, the airflow distributor only diverts a portion of the airflow output from the internal fan 5 to form a jet, while the remaining airflow from the internal fan 5 continues to flow axially, participating in the overall circulation of the enclosed cavity. This composite internal cooling scheme, combining overall circulation with local jets, maintains the overall air circulation within the enclosed cavity to achieve global heat collection and transfer, while also applying strong and concentrated local convective cooling to the surface of the core components where heat generation is most concentrated and heat flux density is highest. This effectively solves the problem of insufficient heat transfer capacity caused by the thickening of the flow boundary layer in high heat flux density areas.

[0037] In one specific embodiment, a thermoelectric cooler is attached to the inner or outer surface of at least one end cap of the cylindrical housing 2. The thermoelectric cooler is a Peltier effect-based thermoelectric cooling device with two working surfaces: a cold end and a hot end. When a direct current passes through, heat is pumped from the cold end to the hot end, causing the cold end temperature to decrease and the hot end temperature to increase. When the thermoelectric cooler is attached to the inner surface of the end cap, its cold end is in thermal contact with the inner surface of the end cap or with the circulating gas in the enclosed cavity through a heat-conducting medium. Its hot end conducts heat to the sidewalls of the cylindrical housing 2 and the external cooling components through the end cap body. When the thermoelectric cooler is attached to the outer surface of the end cap, its cold end absorbs heat from the gas in the enclosed cavity through the end cap body, while its hot end is directly exposed to the external cooling medium or thermally connected to the external cooling components. The activation and deactivation of the thermoelectric cooler are controlled by a controller based on readings from temperature sensors arranged within the enclosed cavity. Under normal operating conditions, external passive cooling is sufficient to maintain the internal temperature within a safe range, and the thermoelectric cooler remains in the off state, consuming no additional electrical energy. When fiber lasers operate in extremely high-temperature environments, such as inside a cabinet under direct sunlight in summer, the temperature of the external cooling medium is already high. Passive heat dissipation reduces the temperature difference, leading to a significant decrease in heat dissipation capacity. When the temperature inside the sealed cavity continues to rise and exceeds a preset safety threshold, the controller activates the power supply circuit for the thermoelectric cooler. The thermoelectric cooler then begins to operate, actively pumping heat from the end cap and the air inside the cavity to the external cooling components. This active cooling process adds an extra cooling driving force to the external passive heat dissipation, forcibly expelling heat against the original temperature difference. This overcomes the limitations of relying solely on the temperature difference of the external cooling medium for heat dissipation, ensuring the safe operation of fiber lasers under harsh high-temperature conditions.

[0038] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, nor is it limited to fiber lasers. Devices and structures not described in detail herein should be understood as being implemented in a manner common to the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the protection scope of the present invention.

Claims

1. A fiber laser, characterized by, include: The cylindrical shell structure is made of thermally conductive material and has cylindrical sidewalls and end caps at both ends. The end caps are sealed to the sidewalls to form a closed cavity. A heating element is installed in a closed cavity and is in thermal contact with the inner surface of the side wall and / or the inner surface of the end cap. The heating element includes a pump source and an optical fiber assembly. An internal fan, fixed to the inside of at least one end cover, has its rotation axis parallel or coincident with the central axis of the housing. It is used to agitate the gas in the closed cavity and force the gas to flow axially and diffuse radially at the end cover to form a circulating airflow, which transfers the heat generated by the heating element to the inner surface of the side wall and the inner surface of the two end covers. An external cooling assembly is mounted on the outer surface of a sidewall and includes multiple heat dissipation fins arranged along the outer surface of the sidewall, as well as a detachably mounted forced convection device for forcing the cooling medium to flow through the heat dissipation fins. When the fiber laser is working, it is placed entirely in the cooling medium. The forced convection device is selectively either an air-cooled fan or a liquid-cooled forced flow component, depending on the type of cooling medium, to achieve active and passive heat dissipation in coordination with the external environment and to improve the internal temperature uniformity.

2. The fiber laser of claim 1, wherein: There are two sets of internal fans, which are respectively set on the inner side of the two end caps, and at least one internal fan is installed on the inner side of each end cap. The two sets of internal fans work together to drive the gas in the closed cavity to form a circulating airflow that runs through the entire cavity.

3. The fiber laser of claim 1, wherein: The heat dissipation fins extend circumferentially and / or axially along the sidewall and are integrally formed with the sidewall or fixed by welding; the cylindrical structure shell is made of aluminum, copper or thermally conductive composite material, and the cross-section of the cylindrical structure shell is circular, square or rectangular.

4. The fiber laser of claim 1, wherein: When the cooling medium is air, the forced convection device includes an air guide shroud and an air-cooled fan, with the air guide shroud covering the periphery of the heat dissipation fins.

5. The fiber laser of claim 1, wherein: When the cooling medium is liquid, the forced convection device includes a liquid pump and a liquid jet nozzle array, which is arranged around the sidewall or along the axial direction to spray cooling liquid onto the surface of the heat sink fins.

6. The fiber laser of claim 1, wherein: Fiber lasers also include heat pipes, with one end of the heat pipe being thermally connected to the heat-generating component or the inner surface of the sidewall, and the second end being thermally connected to the heat dissipation fins to provide an auxiliary heat conduction path.

7. The fiber laser of claim 1, wherein: A phase change material layer is attached to the inner wall of the cylindrical structure shell and / or the inner side of the end caps at both ends. The phase change material layer is located between the inner wall of the closed cavity and the internal circulating gas. The phase change material layer consists of the encapsulation shell and the solid-liquid phase change material filled in the encapsulation shell. The phase change temperature range of the phase change material is set to be higher than the rated operating temperature of the laser and lower than the maximum allowable operating temperature of the laser.

8. The fiber laser according to claim 1, characterized in that: The sealed cavity is equipped with a flow guiding structure, which includes spiral flow guiding ribs arranged circumferentially along the inner wall of the cylindrical shell or flow guiding baffles arranged axially. The spiral flow guiding ribs or flow guiding baffles are connected to the inner wall of the cylindrical shell, dividing the interior of the sealed cavity into multiple interconnected airflow channels. An internal fan drives the gas to flow along the airflow channels, so that the gas flows sequentially over the surfaces of the pump source and the optical fiber assembly, and then spirals forward or axially reverses forward along the inner wall of the cylindrical shell, finally uniformly scouring the inner sides of the end caps at both ends.

9. The fiber laser according to claim 8, characterized in that: Heat dissipation plates are attached to the inner sides of the end caps at both ends. The heat dissipation plates are thermally connected to the cylindrical shell structure to rapidly diffuse the heat carried by the circulating gas to the entire end face.

10. The fiber laser according to claim 1, characterized in that: The outer surface of the cylindrical shell is provided with standardized mechanical connection interfaces and thermal connection interfaces; the external cooling components are independent, removable and replaceable cooling kits, which are installed on the cylindrical shell through the mechanical connection interfaces and thermal connection interfaces; the cooling kits are configured according to the type of external cooling medium, including a first kit that integrates heat dissipation fins and air-cooled fan for gas cooling medium, and a second kit that integrates heat dissipation fins and liquid-cooled forced flow components for liquid cooling medium.

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