A liquid cladding pumped optical fiber and method of making same

Abstract

The application discloses a kind of optical fiber based on liquid cladding pumping and preparation method thereof, the optical fiber includes single crystal core, inner cladding, outer cladding and liquid cooling circulating unit communicated with outer cladding.The inner cladding is provided with refractive liquid, and its refractive index is slightly less than single crystal core, so that single crystal core and inner cladding form inner total reflection;The refractive index of refractive liquid is less than outer cladding, so that inner cladding and outer cladding form outer total reflection;By adjusting the focus of lens focusing, the pump light is transmitted in the inner cladding, the signal light is transmitted in the single crystal core, the signal light transmitted in the single crystal core is pumped by the pump light, the amplification of signal light is realized, and the pump conversion efficiency and output power are improved.The liquid cooling circulating unit is introduced into the inner cladding by condensation cooling after being extracted, and then circulates cooling, which avoids the mechanical damage caused by the expansion of single crystal core and refractive liquid due to different expansion coefficients at high temperature, and prolongs the service life of the optical fiber.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber technology, and more specifically, relates to an optical fiber based on liquid cladding pumping and its fabrication method. Background Technology

[0002] With the development of high-power laser technology and the performance of silica fiber materials, the power and performance of lasers have been significantly improved. However, limited by the nonlinear effects of fiber materials, stimulated Brillouin scattering occurs when the power exceeds a certain threshold, preventing further increases in the power of narrow-linewidth lasers. Unlike traditional silica fibers, single-crystal fibers possess higher thermal conductivity, lower doping concentration, and lower Brillouin scattering coefficients. Using single-crystal fibers as the gain medium for fiber lasers allows for better thermal management of narrow-linewidth lasers, theoretically achieving an average power more than 10 times that of silica fiber lasers, thus breaking through the power bottleneck of fiber lasers. Although single-crystal fibers exhibit superior physicochemical properties, research on them is still in its initial stages compared to the already industrialized silica fibers. Many application technology problems remain to be solved in the application of high-power fiber lasers, among which the cladding preparation of single-crystal fibers is one of the most pressing issues. Currently, the cladding fabrication of single-crystal optical fibers involves two steps: first, a single-crystal fiber core doped with rare-earth elements is fabricated; then, a glass liner or a single-crystal material without rare-earth elements is used as the cladding. Each method has its advantages and disadvantages. The fabrication of glass cladding for single-crystal fibers is simple, but the significant difference in thermal properties between glass and single-crystal fiber makes them prone to separation and detachment in high-power lasers. Furthermore, the large difference in refractive index between the two can easily lead to multimode transmission. While the cladding and core of all-single-crystal fibers have a small difference in refractive index and similar thermal properties, their fabrication process is complex and immature, potentially resulting in cladding that is not axially symmetric, fractured, or has an irregular cross-sectional shape.

[0003] Patent 112162347A discloses a novel liquid sapphire fiber cladding and its preparation method. The cladding liquid is introduced to fill the space between the capillary glass tube and the sapphire fiber, replacing the existing solid cladding method and avoiding cladding cracking caused by the mismatch of expansion coefficients under high temperature conditions. However, it has the following problems: (1) The refractive index of the cladding liquid used is only 1.60-1.71. For single crystal fibers with higher refractive indices, such as YAG and LuAG, which are commonly used single crystal fiber materials on the market, the difference in refractive index between the two is large, which is not conducive to producing high beam quality; (2) The liquid cladding fiber disclosed in the patent still adopts conventional core pumping in use. Its transmitted optical power is still limited by the doping concentration of the core itself (the higher the doping concentration, the shorter the fiber length used). It cannot give full play to the advantages of single crystal fiber over traditional fiber, nor can it achieve high-power laser output; (3) The patent uses the core and multimode fiber fusion splicing method to transmit light. The multimode fiber and single crystal fiber are made of different materials, making fusion difficult. Even if the fusion is successful, the optical power loss is far beyond the normal index, and its practicality is not strong; (4) The single crystal fiber, liquid cladding and capillary glass tube work in a high-temperature environment. The expansion rates of the three are inconsistent. Long-term use can lead to mechanical damage, resulting in a decrease in fiber transmission power and a decrease in fiber life. Summary of the Invention

[0004] To address the problems of poor beam quality, limited transmission power, and inconsistent expansion rates in different parts of the fiber, which can easily lead to mechanical damage at high temperatures, existing liquid-clad optical fibers offer a solution based on liquid-clad pumping. By using an inner cladding refractive liquid with a refractive index close to that of the fiber core, high-performance beam transmission is achieved. The double-clad structure pumping removes power limitations during laser transmission. Furthermore, a liquid-cooling circulation unit circulates and cools the inner cladding refractive liquid, extending the fiber's lifespan.

[0005] To achieve the above objectives, the present invention provides an optical fiber based on liquid cladding pumping, comprising a single-crystal fiber core with a first coating layer on its light-gathering end face, exhibiting high reflectivity for pump light and high transmittance for signal light; an outer cladding layer coaxially arranged around the outside of the single-crystal fiber core, with a second coating layer on its light-gathering end face, exhibiting high transmittance for pump light; and an inner cladding layer disposed within a sealed space between the single-crystal fiber core and the outer cladding layer, filled with a refractive liquid; the refractive index of the refractive liquid is slightly lower than that of the single-crystal fiber core, resulting in total internal reflection within the single-crystal fiber core; the refractive index of the refractive liquid... The inner cladding layer is larger than the outer cladding layer, causing total internal reflection within the inner cladding layer; and a liquid-cooled circulation unit connected to the outer cladding layer, which draws out the refractive liquid, condenses and cools it, and then inputs it into the inner cladding layer for circulating cooling; by adjusting the focusing focal length of the lens, the pump light is transmitted through the second coating layer in the inner cladding layer, and the signal light is transmitted through the first coating layer in the single-crystal fiber core. High-power laser is output as needed. The pump light pumps the signal light transmitted in the single-crystal fiber core, thereby amplifying the signal light and improving the pump conversion efficiency and output power.

[0006] Furthermore, the refractive liquid is composed of diiodomethane, silicone oil, and sulfur, with a weight ratio of 50:7:3.

[0007] Furthermore, the refractive index of the refractive liquid is 1.74-1.78 in the 1-micron wavelength range.

[0008] Furthermore, the single-crystal fiber core preparation material includes any one of lutetium aluminum garnet, yttrium aluminum garnet, and CALGO as the substrate, and is made by doping with rare earth elements.

[0009] Furthermore, the core diameter and length of the single crystal fiber core are not limited, and the refractive index is above 1.80.

[0010] Furthermore, the refractive index of the outer cladding layer is 1.45 in the 1-micron wavelength band, and the material used to make it is a quartz glass tube, which has a hollow tubular structure with symmetrical central holes on both end faces; the inner diameter of the central hole is adapted to the outer diameter of the single crystal fiber core.

[0011] Furthermore, the cooling unit includes a liquid guide pipe and a condenser, as well as a liquid outlet and a liquid inlet located on the outer sheath pipe; the liquid outlet and the liquid inlet are respectively connected to the input end and the output end of the condenser through the liquid guide pipe.

[0012] Furthermore, the cooling unit also includes a clamping water-cooling fixture and a water-cooling circulation machine. The clamping water-cooling fixture includes a clamping hole, wherein the clamping hole is adapted to the outer cladding structure, and the outer cladding can be clamped in the hole, and the heat is conducted to the clamping water-cooling fixture made of a high thermal conductivity material for heat dissipation through the contact surface.

[0013] Furthermore, the clamping water-cooled fixture also includes an inlet and an outlet; the inlet and outlet are respectively connected to the input and output pipes of the water-cooling circulator, and the clamping water-cooled fixture is cooled by water-cooling circulation.

[0014] According to another aspect of the present invention, a method for fabricating optical fibers based on liquid cladding pumping is also provided, comprising the following steps:

[0015] S100: Uses any one of lutetium aluminum garnet, yttrium aluminum garnet, and CALGO as the substrate, and does it with rare earth elements to make a single crystal fiber core, with no limit on the core diameter and length; the first coating layer is deposited on the light-inlet end face of the single crystal fiber core to make the light-inlet end of the single crystal fiber core highly transparent to the signal light and highly reflective to the pump light;

[0016] S200: The outer cladding is made of a quartz glass tube with a refractive index of 1.45 in the 1-micron band. Symmetrical central holes with inner diameters matching the outer diameter of the single-crystal fiber core are opened at both ends of the quartz glass tube. Liquid outlet and liquid inlet are opened on the body of the quartz glass tube respectively. A second coating layer is coated on the light-inlet end of the quartz glass tube to make the light-inlet end of the quartz glass tube highly transparent to the pump light.

[0017] S300: The monocrystalline fiber core is placed in the quartz glass tube through the central hole, with both ends of the monocrystalline fiber core exposed to the air, extending beyond the glass tube port by an appropriate length; glue is used to cure and seal the contact point between the monocrystalline fiber core and the central hole, so that the quartz glass tube and the monocrystalline fiber core form a sealed space.

[0018] S400: A refractive liquid is prepared by mixing diiodomethane, silicone oil and sulfur in a ratio of 50:7:3.

[0019] S500: Connect the condenser output end and the liquid inlet through the pipeline via the liquid guide pipe. Place the liquid outlet and the condenser output end in the refractive liquid through the pipeline respectively. Start the condenser to make the refractive liquid circulate in the pipeline, filling the sealed space to form an inner cladding. After the air bubbles in the circulation pipeline are completely discharged, use a butt joint to connect the pipeline connecting the liquid outlet and the condenser output end into one piece.

[0020] S600: The quartz glass tube is placed on a clamping water-cooled fixture made of a high thermal conductivity material for clamping, and the water-cooling circulator is connected to the pipe of the clamping water-cooled fixture. The clamping water-cooled fixture is cooled by water-cooling circulation to complete the optical fiber fabrication work based on liquid cladding pump.

[0021] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0022] 1. The present invention provides an optical fiber based on liquid cladding pumping, wherein the refractive index of the refractive liquid selected for the inner cladding is lower than that of the single-crystal fiber core, resulting in total internal reflection within the inner cladding; the refractive index of the refractive liquid is higher than that of the outer cladding, resulting in total internal reflection within the inner cladding; by adjusting the focusing focal length of the lens, the pump light is transmitted through the first coating layer in the inner cladding 2, and the signal light is transmitted through the second coating layer in the single-crystal fiber core. Since the refractive liquid is not doped with rare earth ions, the uniformity of pump light power absorption is improved, therefore the power value of the pump light is no longer limited when it is transmitted within the inner cladding 2, and high-power laser can be output as needed.

[0023] 2. The present invention provides an optical fiber based on liquid cladding pumping, which, by selecting a refractive liquid with a refractive index slightly lower than that of the outer cladding, facilitates high-quality beam transmission.

[0024] 3. The present invention provides an optical fiber based on liquid cladding pump, which, by incorporating a liquid cooling circulation unit, draws out the refractive liquid, condenses and cools it, and then inputs it into the inner cladding for circulating cooling. Furthermore, a clamping water-cooling fixture, in conjunction with a water-cooling circulation machine, circulates water cooling through a quartz glass tube in the outer cladding, achieving a dual cooling and heat dissipation effect on the optical fiber. This avoids mechanical damage to the single-crystal fiber core and the refractive liquid due to their different expansion coefficients, thus extending the service life of the optical fiber. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an optical fiber based on liquid cladding pumping in the first embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the outer cladding layer in the first embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of the water-cooling fixture in the first embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the process steps of a liquid cladding pump-based optical fiber fabrication method according to the second embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the structure of a fiber amplifier based on liquid cladding pumping in the third embodiment of the present invention.

[0030] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-single crystal fiber core, 2-inner cladding, 3-outer cladding, 301-liquid outlet, 302-liquid inlet, 303-center hole, 4-signal optical module, 5-first focusing lens, 6-dichroic mirror, 7-pump source module, 8-second focusing lens, 9-liquid guide tube, 10-condenser, 11-clamping water-cooling fixture, 111-water inlet, 112-water outlet, 113-clamping hole. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0032] like Figure 1-4 As shown, the present invention provides an optical fiber based on liquid cladding pump, comprising a single crystal fiber core 1, an outer cladding 3 coaxially disposed on the outside of the single crystal fiber core 1, an inner cladding 2 disposed in a sealed space between the single crystal fiber core 1 and the outer cladding 3, a first coating layer and a second coating layer respectively disposed on the end faces of the single crystal fiber core 1 and the outer cladding 3, and a liquid cooling circulation unit communicating with the outer cladding 3. The inner cladding 2 contains a refractive liquid with a refractive index slightly lower than that of the single-crystal fiber core 1, resulting in total internal reflection within the single-crystal fiber core 1. The outer cladding 3 has a refractive index lower than that of the refractive liquid, resulting in total external reflection within the inner cladding. The inner cladding 2 and outer cladding 3 form a double-cladding structure. By adjusting the focusing focal length, the pump light is transmitted through the first coating layer in the inner cladding 2, while the signal light is transmitted through the second coating layer in the single-crystal fiber core 1. Since the refractive liquid is not doped with rare-earth ions, the uniformity of pump light power absorption is improved. Therefore, the power value of the pump light is no longer limited when it is transmitted within the inner cladding 2, and high-power laser can be output as needed. By pumping the signal light transmitted within the single-crystal fiber core 1 with the pump light, the signal light is amplified, improving the pump conversion efficiency and output power. The liquid cooling circulation unit includes a liquid guide pipe 9 and a condenser 10. By drawing out the refractive liquid, condensing and cooling it, and then inputting it into the inner cladding 2 for circulation cooling, mechanical damage caused by the difference in expansion coefficients between the single crystal fiber core 1 and the refractive liquid is avoided, thus extending the service life of the optical fiber.

[0033] In the first embodiment of the present invention, as Figure 1-2 As shown, the outer cladding layer 3 is a quartz glass tube with a refractive index of 1.45 in the 1-micron wavelength range. It has a hollow tubular structure with symmetrical central holes 303 on both end faces. The inner diameter of the central hole 303 is compatible with the outer diameter of the single-crystal fiber core 1. The single-crystal fiber core 1 can be inserted into the outer cladding layer 3 through the central hole 303, and the contact point is sealed with adhesive. The light-gathering end face of the outer cladding layer 3 is provided with a second coating layer, which has high transmittance to pump light.

[0034] The matrix material of the single-crystal fiber core 1 is laser crystals such as lutetium aluminum garnet (LuAG), yttrium aluminum garnet (YAG), and CALGO, and is doped with rare earth elements such as Yb, Nd, and Er, with a refractive index above 1.80. A first coating layer is provided on the light-gathering end face of the single-crystal fiber core 1, which is highly reflective to pump light and highly transparent to signal light.

[0035] The inner cladding 2 is filled with a refractive liquid with a refractive index value slightly lower than that of the single-crystal fiber core 1. Its refractive index value is 1.74-1.78 in the 1-micron wavelength range, giving the inner cladding 2 a higher refractive index, which is beneficial for high-performance beam transmission (the greater the relative refractive index difference between the single-crystal fiber core and the cladding, the larger the numerical aperture of the optical fiber, resulting in an excessive number of supported modes, which easily leads to the generation of higher-order modes, hindering fundamental mode transmission and thus degrading beam quality). In a specific embodiment of the invention, the refractive liquid is composed of diiodomethane, silicone oil, and sulfur in a weight ratio of 50:7:3, with a viscosity slightly higher than that of water, resulting in good fluidity.

[0036] The cooling unit includes a liquid guide pipe 9 and a condenser 10, as well as an outlet 301 and an inlet 302 located on the outer cladding 3. The outlet 301 and inlet 302 are respectively connected to the input and output ends of the condenser 10 via the liquid guide pipe 9. The condenser 10 can extract and cool the refractive liquid through the outlet 301, and after cooling, it returns to the inner cladding 2 through the inlet 302. The pumping rate of the condenser 10 is the same as the pumping rate, which can avoid cavitation in the inner cladding 2 and enable the refractive liquid to circulate and cool.

[0037] Preferably, the cooling unit further includes a clamping water-cooling fixture 11 and a water-cooling circulation machine. The clamping water-cooling fixture 11 includes an inlet pipe 111, an outlet pipe 112, and a clamping hole 113. The clamping hole 113 is adapted to the structure of the outer cladding 3, allowing the outer cladding 3 to be clamped within the hole. Heat is conducted to the clamping water-cooling fixture 11, made of a high thermal conductivity material, through the contact surface for heat dissipation. The inlet pipe 111 and outlet pipe 112 are respectively connected to the input and output pipes of the water-cooling circulation machine, and the clamping water-cooling fixture 11 is cooled by water-cooling circulation. In this invention, the optical fiber circulates and cools the refractive liquid of the inner cladding 2 through the condenser 10, and uses the clamping water-cooling fixture 11 and the water-cooling circulation machine to circulate and cool the quartz glass tube of the outer cladding 3, achieving a dual cooling and heat dissipation effect for the optical fiber. This avoids mechanical damage caused by the difference in expansion coefficients between the single crystal fiber core 1 and the refractive liquid, extending the service life of the optical fiber.

[0038] In a second embodiment of the present invention, a method for fabricating optical fibers based on liquid cladding pumping is also provided, comprising the following steps:

[0039] S100: A single crystal core 1 is made by using any one of lutetium aluminum garnet (LuAG), yttrium aluminum garnet (YAG), and CALGO as the substrate and doping it with rare earth elements. The core diameter and length are unlimited. A first coating layer is deposited on the light-inlet end face of the single crystal core 1 to make the light-inlet end of the single crystal core 1 highly transparent to signal light and highly reflective to pump light.

[0040] S200: The outer cladding 3 is made of a quartz glass tube with a refractive index of 1.45 in the 1-micron band. A central hole 303 with an inner diameter that matches the outer diameter of the single crystal fiber core 1 is symmetrically opened at both ends of the quartz glass tube. An outlet 301 and an inlet 302 are opened on the body of the quartz glass tube respectively. A second coating layer is coated on the light-inlet end of the quartz glass tube to make the light-inlet end of the quartz glass tube highly transparent to the pump light.

[0041] S300: Place the single crystal fiber core 1 in the quartz glass tube through the central hole 303, with both ends of the single crystal fiber core 1 exposed to the air, extending beyond the appropriate length of the glass tube port; use glue to cure and seal the contact point between the single crystal fiber core 1 and the central hole 303, so that the quartz glass tube and the single crystal fiber core 1 form a sealed space.

[0042] S400: A refractive liquid is prepared by mixing diiodomethane, silicone oil and sulfur in a ratio of 50:7:3.

[0043] S500: Connect the output end of condenser 10 to liquid inlet 302 through liquid guide pipe 9. Place liquid outlet 301 and output end of condenser 10 in the refractive liquid through pipes respectively. Start condenser 10 to make the refractive liquid circulate in the pipe, fill the sealed space to form inner cladding 2. After the air bubbles in the circulation pipe are completely discharged, use a butt joint to connect the pipe connecting liquid outlet 301 and output end of condenser 10 into one piece.

[0044] S600: The quartz glass tube is placed on the clamping water-cooling fixture 11 made of high thermal conductivity material for clamping, and the water-cooling circulator is connected to the pipe of the clamping water-cooling fixture 11. The clamping water-cooling fixture 11 is cooled by water-cooling circulation to complete the optical fiber fabrication work based on liquid cladding pump.

[0045] In the third embodiment of the present invention, as Figure 5 As shown, a liquid-clad pumped fiber amplifier is also provided, comprising a signal light module 4, a first focusing mirror 5, a dichroic mirror 6, a pump source module 7, a second focusing mirror 8, and an optical fiber. The signal light module 4 can emit signal light with a wavelength of 1030-1064 nm, and is not limited to fiber lasers or solid-state lasers. The pump source module 7 can emit high-power pump light. The top of the dichroic mirror 6 is coated with a high-transmission film for the signal light wavelength, and the bottom is coated with a high-reflection film for the pump light wavelength.

[0046] When the amplifier is working, by adjusting the position of the first focusing mirror 5, the signal light emitted from the signal light module 4 passes through the first focusing mirror 5 and the dichroic mirror 6 in sequence, and the focused spot size is large enough to couple into the single crystal fiber core 1, so that the signal light can be transmitted within the single crystal fiber core 1. By adjusting the position of the second focusing mirror 8, the pump light emitted from the pump source module 7 passes through the second focusing mirror 2 and is reflected by the dichroic mirror 6, and the focused spot size is large enough to couple into the inner cladding 2, so that the pump light can be transmitted within the inner cladding 2. By pumping the signal light transmitted within the single crystal fiber core 1 with the pump light, the signal light is amplified, and the pump conversion efficiency and output power are improved.

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optical fiber based on liquid cladding pumping, characterized in that, include: The single-crystal fiber core (1) has a first coating layer on its light-inlet end face, which is highly reflective to pump light and highly transparent to signal light; The outer cladding (3) of the coaxial ring is located on the outside of the single crystal fiber core (1), and a second coating layer is provided on its light-inlet end face, which is highly transparent to pump light; An inner cladding layer (2) is located in the sealed space between the single crystal fiber core (1) and the outer cladding layer (3), and is filled with a refractive liquid. The refractive index of the refractive liquid is less than that of the single crystal fiber core (1), so that total internal reflection is formed in the single crystal fiber core (1). The refractive index of the refractive liquid is greater than that of the outer cladding layer (3), so that total external reflection is formed in the inner cladding layer (2). The refractive liquid is composed of diiodomethane, silicone oil and sulfur, with a weight ratio of 50:7:

3. The refractive index of the refractive liquid is 1.74-1.78 in the 1-micron wavelength band. And a liquid cooling circulation unit connected to the outer cladding (3), which draws out the refracting liquid, condenses and cools it, and then inputs it into the inner cladding (2) for circulation cooling; By adjusting the focusing focal length of the lens, the pump light is transmitted through the second coating layer in the inner cladding (2), and the signal light is transmitted through the first coating layer in the single crystal fiber core (1). A high-power laser is output as needed. The signal light transmitted in the single crystal fiber core (1) is pumped by the pump light, which amplifies the signal light and improves the pump conversion efficiency and output power.

2. The optical fiber based on liquid cladding pumping according to claim 1, characterized in that, The single crystal fiber core (1) is made of a laser crystal selected from lutetium aluminum garnet, yttrium aluminum garnet, and CALGO as a substrate and doped with rare earth elements.

3. The optical fiber based on liquid cladding pumping according to claim 2, characterized in that, The core diameter and length of the single crystal fiber core (1) are not limited, and the refractive index is above 1.

80.

4. The optical fiber based on liquid cladding pumping according to claim 1, characterized in that, The refractive index of the outer cladding layer (3) is 1.45 in the 1-micron band. The material used to make it is a quartz glass tube, which is a hollow tubular structure with symmetrical central holes (303) on both ends. The inner diameter of the central hole (303) is matched with the outer diameter of the single crystal fiber core (1).

5. The optical fiber based on liquid cladding pumping according to claim 1, characterized in that, The liquid cooling circulation unit includes a liquid guide pipe (9) and a condenser (10), as well as an outlet (301) and an inlet (302) provided on the outer sheath (3) pipe body; the outlet (301) and the inlet (302) are respectively connected to the input end and the output end of the condenser (10) through the liquid guide pipe (9).

6. The optical fiber based on liquid cladding pumping according to claim 5, characterized in that, The liquid cooling circulation unit further includes a water-cooling clamping fixture (11) and a water-cooling circulation machine. The water-cooling clamping fixture (11) includes a clamping hole (113), wherein: The clamping hole (113) is adapted to the structure of the outer cladding layer (3), and the outer cladding layer (3) can be clamped in the hole. The heat is conducted to the clamping water-cooling fixture (11) made of high thermal conductivity material by the contact surface for heat dissipation.

7. The optical fiber based on liquid cladding pumping according to claim 6, characterized in that, The clamping water-cooling fixture (11) also includes a water inlet (111) and a water outlet (112). The inlet (111) and outlet (112) are connected to the input and output pipes of the water-cooled circulator, respectively, and the water-cooled fixture (11) is cooled by water-cooled circulation.

8. A method for fabricating optical fibers based on liquid cladding pumping, characterized in that, Includes the following steps: S100: A single crystal core (1) is made by using any one of lutetium aluminum garnet, yttrium aluminum garnet and CALGO as the substrate and doping it with rare earth elements. The core diameter and length are unlimited. A first coating layer is deposited on the light-inlet end face of the single crystal core (1) so that the light-inlet end of the single crystal core (1) is highly transparent to the signal light and highly reflective to the pump light. S200: The outer cladding (3) is made of a quartz glass tube with a refractive index of 1.45 in the 1-micron band. A central hole (303) with an inner diameter that matches the outer diameter of the single crystal fiber core (1) is symmetrically opened at both ends of the quartz glass tube. An outlet (301) and an inlet (302) are opened on the body of the quartz glass tube respectively. A second coating layer is coated on the light-inlet end of the quartz glass tube to make the light-inlet end of the quartz glass tube highly transparent to the pump light. S300: Place the single crystal fiber core (1) in the quartz glass tube through the central hole (303), with both ends of the single crystal fiber core (1) exposed to the air, extending beyond the appropriate length of the glass tube port; use glue to cure and seal the contact point between the single crystal fiber core (1) and the central hole (303), so that the quartz glass tube and the single crystal fiber core (1) form a sealed space; S400: A refractive liquid is prepared by mixing diiodomethane, silicone oil and sulfur in a weight ratio of 50:7:

3. S5 00: Connect the output end of the condenser (10) and the inlet (302) through the liquid guide pipe (9) and place the outlet (301) and the output end of the condenser (10) in the refractive liquid through the pipes respectively. Start the condenser (10) to make the refractive liquid circulate in the pipes and fill the sealed space to form an inner cladding (2). After the air bubbles in the circulation pipe are completely discharged, use a connector to connect the pipes connecting the outlet (301) and the output end of the condenser (10) into one piece. S600: The quartz glass tube is placed on a clamping water-cooling fixture (11) made of a high thermal conductivity material and clamped. The water-cooling circulator is connected to the pipe of the clamping water-cooling fixture (11) and the clamping water-cooling fixture (11) is cooled by water-cooling circulation to complete the optical fiber preparation work based on liquid cladding pump.

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