A ytterbium-doped high-power laser optical fiber, a preform and a preparation method thereof

Abstract

This application is applicable to the field of optical fiber technology, and provides a ytterbium-doped high-power laser optical fiber. The core diameter of the optical fiber is 32 - 36 microns, the cladding of the optical fiber is a regular octagon, and the face-to-face distance of the regular octagon is 440 - 470 microns; the doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, the concentration of Yb2O3 is 0.3 - 0.35 mol%, the doping concentration of aluminum element is calculated in the form of Al2O3, the concentration of Al2O3 is 1.9 - 2.2 mol%, the doping concentration of phosphorus element is calculated in the form of P2O5, the concentration of P2O5 is 2.8 - 3.5 mol%, and the rest is SiO2. The refractive index difference between the core and pure quartz is 0.002 - 0.0025; the refractive index profile of the laser optical fiber is flat. The ytterbium-doped high-power laser optical fiber provided by the embodiments of this application has more optimized doping components, a more reasonable design of the core refractive index and the core diameter. Compared with the prior art, the three are more matched. At the same time, the refractive index profile of the prepared ytterbium-doped optical fiber in the Yb2O3-Al2O3-P2O5 system is flat, enabling the optical fiber to operate stably and efficiently under high-power conditions.

Description

Technical Field

[0001] This application belongs to the technical field of optical fibers, and particularly relates to a ytterbium-doped high-power laser optical fiber, a preform, and a preparation method thereof. Background Art

[0002] Ytterbium-doped laser optical fiber is the core component of 1-micron fiber lasers. With the development of fiber laser technology, the laser power has developed from the initial watt level to the ten-thousand-watt level. With the increase in laser power, phenomena such as photon darkening, mode instability, and nonlinear effects are likely to occur in the optical fiber, restricting the further increase in laser power.

[0003] An important factor restricting the increase in laser power is the photon darkening phenomenon, that is, the laser output decreases with time. The method to suppress photon darkening is usually to dope phosphorus pentoxide during the optical fiber preparation process, which has become an industry consensus. However, on the one hand, the addition of phosphorus pentoxide will cause changes in the core refractive index. Too high a refractive index is likely to lead to too many modes in the optical fiber, reducing the mode instability threshold, and too low a refractive index is likely to lead to high bending loss of the optical fiber. On the other hand, the addition of phosphorus pentoxide will also cause the absorption coefficient of the optical fiber to become smaller, making the use length of the optical fiber longer, and the nonlinear gain coefficient of the optical fiber is proportional to the use length of the optical fiber. Increasing the use length means that the optical fiber is more likely to have nonlinear effects under high-power conditions. In order to reduce the power density of the high-power laser optical fiber and reduce laser damage or nonlinear effects caused by too high power density, high-power laser optical fibers often require a larger core size. However, according to where a is the core radius, n 芯 is the core refractive index, n 包 is the cladding refractive index, λ is the laser wavelength, the larger the V value, the more modes are transmitted in the optical fiber, and the worse the beam quality. It can be seen from the formula that a large core size will lead to poor beam quality and requires a lower core refractive index to match. In summary, photon darkening is affected by the doping components, and the doping components in turn affect the absorption coefficient and core refractive index of the optical fiber. The core refractive index and core size affect the beam quality of the optical fiber, and the absorption coefficient indirectly affects the nonlinear effect of the optical fiber. Therefore, the core doping components, core refractive index, and core size restrict each other and jointly determine the comprehensive performance of the laser optical fiber under high-power conditions.

[0004] The prior art does not provide a good solution that takes into account the geometric size, doping components, and core refractive index of the optical fiber, resulting in poor performance such as stability and high-efficiency operation performance of the laser optical fiber in the prior art under high-power conditions. Summary of the Invention

[0005] The purpose of the embodiments of this application is to provide a ytterbium-doped high-power laser optical fiber, aiming to solve the problem of poor performance such as stability and high-efficiency operation performance of the laser optical fiber in the prior art under high-power conditions.

[0006] The embodiments of the present application are implemented as follows. A ytterbium-doped high-power laser fiber, the core diameter of the fiber is 32 - 36 microns, the cladding of the fiber is a regular octagon, and the face-to-face distance of the regular octagon is 440 - 470 microns; the doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, the concentration of Yb2O3 is 0.3 - 0.35 mol%, the doping concentration of aluminum element is calculated in the form of Al2O3, the concentration of Al2O3 is 1.9 - 2.2 mol%, the doping concentration of phosphorus element is calculated in the form of P2O5, the concentration of P2O5 is 2.8 - 3.5 mol%, and the rest is SiO2; the refractive index profile of the laser fiber is flat.

[0007] Another object of the embodiments of the present application is to provide a method for preparing a ytterbium-doped high-power laser fiber preform, including the steps of preparing a mother rod by using the MCVD method combined with the solution immersion method, and performing shape processing on the mother rod to obtain a ytterbium-doped high-power laser fiber preform with a regular octagon-shaped cladding and a core-cladding ratio meeting a preset ratio; the step of preparing the mother rod by using the MCVD method combined with the solution immersion method specifically includes: a loose body deposition step, a solution immersion step, a drying step, a heat treatment step, and a collapsing step; among them, the collapsing step specifically includes eight steps, and the conditions are controlled as follows:

[0008] The first step: Combust hydrogen: 78 - 82 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 500 - 800 milliliters per minute of oxygen; torch moving speed: 55 millimeters per minute.

[0009] The second step: Combust hydrogen: 82 - 86 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 500 - 800 milliliters per minute of oxygen; torch moving speed: 50 millimeters per minute.

[0010] The third step: Combust hydrogen: 86 - 90 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 400 - 700 milliliters per minute of oxygen; torch moving speed: 45 millimeters per minute.

[0011] The fourth step: Combust hydrogen: 90 - 94 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 400 - 700 milliliters per minute of oxygen; torch moving speed: 40 millimeters per minute.

[0012] The fifth step: Combust hydrogen: 94 - 98 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 300 - 600 milliliters per minute of oxygen; torch moving speed: 35 millimeters per minute.

[0013] Step 6: Burn hydrogen: 98 - 102 liters per minute, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 300 - 600 milliliters per minute of oxygen; blowtorch moving speed: 30 millimeters per minute.

[0014] Step 7: Burn hydrogen: 102 - 106 liters per minute, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 200 - 400 milliliters per minute of oxygen; blowtorch moving speed: 25 millimeters per minute.

[0015] Step 8: Burn hydrogen: 110 - 114 liters per minute, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 100 - 200 milliliters per minute of oxygen; blowtorch moving speed: 10 millimeters per minute.

[0016] Another object of the embodiments of the present application is to provide a ytterbium-doped high-power laser fiber preform, which is obtained by the above-mentioned method for preparing a ytterbium-doped high-power laser fiber preform.

[0017] Another object of the embodiments of the present application is to provide a method for preparing a ytterbium-doped high-power laser fiber. The ytterbium-doped high-power laser fiber preform prepared by the above method is drawn to obtain a ytterbium-doped high-power laser fiber.

[0018] The ytterbium-doped high-power laser fiber provided by the embodiments of the present application has more optimized doping components, more reasonable design of the core refractive index and core diameter. Compared with the prior art, the three are more matched. At the same time, the refractive index profile of the Yb2O3 - Al2O3 - P2O5 system ytterbium-doped fiber prepared is flat, enabling the fiber to operate stably and efficiently under high-power conditions. Description of the Drawings

[0019] Figure 1 is the refractive index profile diagram of the fiber in Embodiment 1 of the present application;

[0020] Figure 2 is the laser efficiency diagram of the fiber in Embodiment 1 of the present application;

[0021] Figure 3 is the beam quality parameter diagram of the fiber in Embodiment 1 of the present application;

[0022] Figure 4 is the laser spectrum diagram of the fiber in Embodiment 1 of the present application;

[0023] Figure 5 is the diagram of the change relationship between the output power and time of the fiber in Embodiment 1 of the present application;

[0024] Figure 6 is the refractive index profile diagram of the fiber in Embodiment 2 of the present application;

[0025] Figure 7It is the laser efficiency diagram of the optical fiber in Embodiment 2 of the present application;

[0026] Figure 8 It is the beam quality parameter diagram of the optical fiber in Embodiment 2 of the present application;

[0027] Figure 9 It is the laser spectrum diagram of the pre-optical fiber in Embodiment 2 of the present application;

[0028] Figure 10 It is the diagram of the variation relationship between the output power and time of the optical fiber in Embodiment 2 of the present application;

[0029] Figure 11 It is the laser efficiency diagram of the optical fiber in Comparative Example 1 of the present application;

[0030] Figure 12 It is the refractive index profile diagram of the optical fiber in Comparative Example 2 of the present application;

[0031] Figure 13 It is the laser spectrum diagram of the optical fiber in Comparative Example 2 of the present application;

[0032] Figure 14 It is the diagram of the variation relationship between the output power and time of the optical fiber in Comparative Example 3 of the present application;

[0033] Figure 15 It is the beam quality parameter diagram of the optical fiber in Comparative Example 4 of the present application. Detailed implementation manners

[0034] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application 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 only used to explain the present application and are not used to limit the present application.

[0035] The embodiment of the present application provides a ytterbium-doped high-power laser optical fiber. The core diameter of the optical fiber is 32-36 microns. The cladding of the optical fiber is a regular octagon, and the face-to-face distance of the regular octagon is 440-470 microns. The doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, and the concentration of Yb2O3 is 0.3-0.35 mol%. The doping concentration of aluminum element is calculated in the form of Al2O3, and the concentration of Al2O3 is 1.9-2.2 mol%. The doping concentration of phosphorus element is calculated in the form of P2O5, and the concentration of P2O5 is 2.8-3.5 mol%. The rest is SiO2. The refractive index profile of the laser optical fiber is flat.

[0036] The ytterbium-doped high-power laser fiber provided by the embodiment of the present application has more optimized doping components, and the design of the core refractive index and the core diameter is more reasonable. Compared with the prior art, the three are more matched. At the same time, the refractive index profile of the prepared Yb2O3-Al2O3-P2O5 system ytterbium-doped optical fiber is flat, enabling the optical fiber to operate stably and efficiently under high-power conditions.

[0037] As a preferred embodiment of the present invention, the core diameter of the ytterbium-doped high-power laser fiber is 34 μm, the cladding of the optical fiber is a regular octagon, and the face-to-face distance of the regular octagon is 460 μm; the doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, the concentration of Yb2O3 is 0.32 mol%, the doping concentration of aluminum element is calculated in the form of Al2O3, the concentration of Al2O3 is 2 mol%, the doping concentration of phosphorus element is calculated in the form of P2O5, the concentration of P2O5 is 3.1 mol%, and the rest is SiO2; the refractive index profile of the laser optical fiber is flat.

[0038] As a preferred embodiment of the present invention, the core diameter of the ytterbium-doped high-power laser fiber is 33 μm, the cladding of the optical fiber is a regular octagon, and the face-to-face distance of the regular octagon is 465 μm; the doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, the concentration of Yb2O3 is 0.3 mol%, the doping concentration of aluminum element is calculated in the form of Al2O3, the concentration of Al2O3 is 2.1 mol%, the doping concentration of phosphorus element is calculated in the form of P2O5, the concentration of P2O5 is 3.2 mol%, and the rest is SiO2; the refractive index profile of the laser optical fiber is flat.

[0039] The embodiment of the present invention provides a method for preparing a preform of the above-mentioned ytterbium-doped high-power laser fiber, including the steps of preparing a mother rod by using the MCVD method combined with the solution immersion method, and performing shape processing on the mother rod to obtain a ytterbium-doped high-power laser fiber preform with a regular octagon-shaped cladding and a core-cladding ratio meeting a preset ratio; the step of preparing the mother rod by using the MCVD method combined with the solution immersion method specifically includes: a loose body deposition step, a solution immersion step, a drying step, a heat treatment step, and a collapse step; among them, the collapse step specifically includes eight steps, and the condition control is as follows:

[0040] The first step: Combust hydrogen: 78 - 82 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 500 - 800 milliliters per minute of oxygen; the moving speed of the blowtorch: 55 millimeters per minute.

[0041] The second step: Combust hydrogen: 82 - 86 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 500 - 800 milliliters per minute of oxygen; the moving speed of the blowtorch: 50 millimeters per minute.

[0042] Step 3: Burn hydrogen: 86 - 90 L / min, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 400 - 700 mL / min of oxygen; torch moving speed: 45 mm / min.

[0043] Step 4: Burn hydrogen: 90 - 94 L / min, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 400 - 700 mL / min of oxygen; torch moving speed: 40 mm / min.

[0044] Step 5: Burn hydrogen: 94 - 98 L / min, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 300 - 600 mL / min of oxygen; torch moving speed: 35 mm / min.

[0045] Step 6: Burn hydrogen: 98 - 102 L / min, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 300 - 600 mL / min of oxygen; torch moving speed: 30 mm / min.

[0046] Step 7: Burn hydrogen: 102 - 106 L / min, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 200 - 400 mL / min of oxygen; torch moving speed: 25 mm / min.

[0047] Step 8: Burn hydrogen: 110 - 114 L / min, hydrogen-oxygen combustion ratio: 2.0 - 2.3, gas in the tube: 100 - 200 mL / min of oxygen; torch moving speed: 10 mm / min.

[0048] It should be noted here that the loose body deposition step, solution immersion step, drying step, and heat treatment step in the embodiments of the present invention can be carried out with reference to the literature (Materials for high-power fiber lasers, J.Kirchhof, 2006). In practical applications, those skilled in the art can understand that preparation processes similar to the above steps can replace the above steps. The selection of the steps and conditions of the loose body deposition step, solution immersion step, drying step, and heat treatment step in this embodiment does not limit the protection scope of the present invention.

[0049] A ytterbium-doped high-power laser fiber preform provided by an embodiment of the present invention is prepared by the above-mentioned method for preparing a ytterbium-doped high-power laser fiber preform.

[0050] A ytterbium-doped high-power laser fiber preform provided by an embodiment of the present invention has more optimized doping components of the fiber prepared from the preform, more reasonable designs of the core refractive index and the core diameter. Compared with the prior art, the three are more matched. At the same time, the refractive index profile of the ytterbium-doped fiber in the Yb2O3-Al2O3-P2O5 system prepared is flat, enabling the fiber to operate stably and efficiently under high-power conditions.

[0051] As a preferred embodiment of the present invention, the condition control of the eight steps of the collapsing step is as follows:

[0052] The first step: Combust hydrogen: 80 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 600 milliliters per minute of oxygen; torch moving speed: 55 millimeters per minute.

[0053] The second step: Combust hydrogen: 84 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 600 milliliters per minute of oxygen; torch moving speed: 50 millimeters per minute.

[0054] The third step: Combust hydrogen: 88 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 500 milliliters per minute of oxygen; torch moving speed: 45 millimeters per minute.

[0055] The fourth step: Combust hydrogen: 92 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 500 milliliters per minute of oxygen; torch moving speed: 40 millimeters per minute.

[0056] The fifth step: Combust hydrogen: 96 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 400 milliliters per minute of oxygen; torch moving speed: 35 millimeters per minute.

[0057] The sixth step: Combust hydrogen: 100 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 400 milliliters per minute of oxygen; torch moving speed: 30 millimeters per minute.

[0058] The seventh step: Combust hydrogen: 104 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 300 milliliters per minute of oxygen; torch moving speed: 25 millimeters per minute.

[0059] The eighth step: Combust hydrogen: 112 liters per minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 100 milliliters per minute of oxygen; torch moving speed: 10 millimeters per minute.

[0060] As a preferred embodiment of the present invention, the condition control of the eight steps of the collapsing step is as follows:

[0061] Step 1: Burn hydrogen: 78 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 800 milliliters per minute of oxygen; torch moving speed: 55 millimeters per minute.

[0062] Step 2: Burn hydrogen: 82 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 800 milliliters per minute of oxygen; torch moving speed: 50 millimeters per minute.

[0063] Step 3: Burn hydrogen: 86 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 700 milliliters per minute of oxygen; torch moving speed: 45 millimeters per minute.

[0064] Step 4: Burn hydrogen: 90 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 700 milliliters per minute of oxygen; torch moving speed: 40 millimeters per minute.

[0065] Step 5: Burn hydrogen: 94 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 600 milliliters per minute of oxygen; torch moving speed: 35 millimeters per minute.

[0066] Step 6: Burn hydrogen: 98 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 600 milliliters per minute of oxygen; torch moving speed: 30 millimeters per minute.

[0067] Step 7: Burn hydrogen: 102 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 400 milliliters per minute of oxygen; torch moving speed: 25 millimeters per minute.

[0068] Step 8: Burn hydrogen: 110 liters per minute, hydrogen-oxygen combustion ratio: 2.3, gas inside the tube: 200 milliliters per minute of oxygen; torch moving speed: 10 millimeters per minute.

[0069] Furthermore, the present invention provides a method for preparing ytterbium-doped high-power laser fiber, which is obtained by drawing the ytterbium-doped high-power laser fiber preform prepared by the above method.

[0070] The method for preparing ytterbium-doped high-power laser fiber provided by the embodiments of the present application has more optimized doping components, more reasonable design of the core refractive index and core diameter. Compared with the prior art, the three are more matched. At the same time, the refractive index profile of the Yb2O3-Al2O3-P2O5 system ytterbium-doped fiber prepared is flat, enabling the fiber to operate stably and efficiently under high-power conditions.

[0071] The following gives examples of some embodiments of the present application, and the purpose is not to limit the scope of the present application.

[0072] Example 1

[0073] A high-power laser fiber preform is prepared through the following steps:

[0074] Loose body deposition: The inner wall of a quartz tube is etched by sulfur hexafluoride and oxygen at high temperature, and then a silicon dioxide loose body is formed by reacting raw material gases such as silicon tetrachloride at about 1500 °C.

[0075] Solution immersion: An ethanol solution of the required dopant is prepared, and the above-mentioned loose body is immersed in the solution for more than 30 minutes.

[0076] Drying: After immersion, chlorine gas and the like are introduced into the quartz tube to dehydrate and dry the loose body at 1100 °C.

[0077] Heat treatment: Oxygen gas and the like are introduced into the quartz tube for heat treatment at 1400 °C.

[0078] Collapse step: The collapse step includes eight steps, and the conditions are controlled as follows:

[0079] First step: Combust hydrogen: 80 L / min, hydrogen-oxygen combustion ratio: 2.2, gas in the tube: 600 mL / min oxygen; torch moving speed: 55 mm / min.

[0080] Second step: Combust hydrogen: 84 L / min, hydrogen-oxygen combustion ratio: 2.2, gas in the tube: 600 mL / min oxygen; torch moving speed: 50 mm / min.

[0081] Third step: Combust hydrogen: 88 L / min, hydrogen-oxygen combustion ratio: 2.2, gas in the tube: 500 mL / min oxygen; torch moving speed: 45 mm / min.

[0082] Fourth step: Combust hydrogen: 92 L / min, hydrogen-oxygen combustion ratio: 2.2, gas in the tube: 500 mL / min oxygen; torch moving speed: 40 mm / min.

[0083] Fifth step: Combust hydrogen: 96 L / min, hydrogen-oxygen combustion ratio: 2.2, gas in the tube: 400 mL / min oxygen; torch moving speed: 35 mm / min.

[0084] Sixth step: Combust hydrogen: 100 L / min, hydrogen-oxygen combustion ratio: 2.2, gas in the tube: 400 mL / min oxygen; torch moving speed: 30 mm / min.

[0085] Seventh step: Combust hydrogen: 104 L / min, hydrogen-oxygen combustion ratio: 2.2, gas in the tube: 300 mL / min oxygen; torch moving speed: 25 mm / min.

[0086] Step 8: Burn hydrogen: 112 liters per minute, hydrogen-oxygen combustion ratio: 2.2, gas inside the tube: 100 milliliters per minute of oxygen; torch moving speed: 10 millimeters per minute, to obtain the mother rod.

[0087] External shape processing: Perform external shape processing on the mother rod to obtain a ytterbium-doped high-power laser fiber preform with a cladding in the shape of a regular octagon and a core-cladding ratio meeting the preset ratio.

[0088] Drawing: Perform drawing on the preform to produce a ytterbium-doped high-power laser fiber. The core diameter of this fiber is 34 microns, the cladding is in the shape of a regular octagon, and the distance between opposite sides of the regular octagon is 460 microns; the core doping components are Yb2O3: 0.32 mol%, Al2O3: 2 mol%, P2O5: 3.1 mol%, and the rest is SiO2.

[0089] Figure 1 This is the refractive index profile diagram of the fiber in Example 1 of the present invention. The refractive index distribution is measured using a P104 refractive index distribution tester. The refractive index distribution is flat, and the difference in refractive index from pure quartz is 0.0023.

[0090] Figure 2 This is the laser efficiency diagram of the fiber in Example 1 of the present invention tested using a MOPA amplification structure. After stripping the cladding light, the laser efficiency is 82.1%. Due to being limited by the pump source power, a laser output of 6400 watts is achieved. Those skilled in the art can understand that in the case of a larger pump source power, a laser output greater than 6400 watts can be achieved.

[0091] Figure 3 This is the beam quality parameter diagram of the fiber in Example 1 of the present invention obtained by testing with PRIMES software, and its bpp value is 2.840.

[0092] Figure 4 This is the laser spectrum diagram of the fiber in Example 1 of the present invention recorded using a spectrometer. The recording result is that no Raman peak is observed at the 1130 nm position.

[0093] Figure 5 This is to record the relationship between the output power and time (aging curve) of the fiber in Example 1 of the present invention. The power drops by 0.8% after 500 hours.

[0094] Example 2

[0095] Prepare a high-power laser fiber preform through the following steps:

[0096] Loose body deposition: Etch the inner wall of the quartz tube by sulfur hexafluoride and oxygen at high temperature, and then react raw material gases such as silicon tetrachloride at about 1500 degrees Celsius to generate a silicon dioxide loose body.

[0097] Solution immersion: Prepare an ethanol solution of the required dopant and immerse the above-mentioned loose body in the solution for more than 30 minutes.

[0098] Drying: After immersion, introduce chlorine gas into the quartz tube and dehydrate and dry the loose body at 1100 °C.

[0099] Heat treatment: Introduce oxygen gas into the quartz tube and perform heat treatment at 1400 °C.

[0100] Collapse step: The collapse step includes eight steps, and the conditions are controlled as follows:

[0101] First step: Burn hydrogen: 78 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 800 mL / min of oxygen; torch moving speed: 55 mm / min.

[0102] Second step: Burn hydrogen: 82 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 800 mL / min of oxygen; torch moving speed: 50 mm / min.

[0103] Third step: Burn hydrogen: 86 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 700 mL / min of oxygen; torch moving speed: 45 mm / min.

[0104] Fourth step: Burn hydrogen: 90 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 700 mL / min of oxygen; torch moving speed: 40 mm / min.

[0105] Fifth step: Burn hydrogen: 94 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 600 mL / min of oxygen; torch moving speed: 35 mm / min.

[0106] Sixth step: Burn hydrogen: 98 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 600 mL / min of oxygen; torch moving speed: 30 mm / min.

[0107] Seventh step: Burn hydrogen: 102 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 400 mL / min of oxygen; torch moving speed: 25 mm / min.

[0108] Eighth step: Burn hydrogen: 110 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 200 mL / min of oxygen; torch moving speed: 10 mm / min to obtain the mother rod.

[0109] Profile processing: Perform profile processing on the mother rod to obtain a ytterbium-doped high-power laser fiber preform with a regular octagon profile for the cladding and a core-cladding ratio meeting the preset ratio.

[0110] Drawing: The master rod is drawn to produce a ytterbium-doped high-power laser fiber. The core diameter of the fiber is 33 microns, the cladding is a regular octagon, and the distance between opposite faces of the regular octagon is 465 microns. The core doping components are Yb2O3: 0.03 mol%, Al2O3: 2.1 mol%, P2O5: 3.2 mol%, and the rest is SiO2.

[0111] Figure 6 This is the refractive index profile diagram of the fiber in Example 2 of the present invention. The refractive index distribution is measured using a P104 refractive index distribution tester. The refractive index distribution is flat, and the difference in refractive index from that of pure quartz is 0.0021.

[0112] Figure 7 This is the laser efficiency diagram of the fiber in Example 2 of the present invention tested using a MOPA amplification structure. After stripping the cladding light, the laser efficiency is 80.1%. Due to the limitation of the pump source power, a laser output of 6260 watts is achieved. Those skilled in the art can understand that a laser output greater than 6260 watts can be achieved with a higher pump source power.

[0113] Figure 8 This is the beam quality parameter diagram of the fiber in Example 2 of the present invention tested using PRIMES software, and its bpp value is 2.904.

[0114] Figure 9 This is the laser spectrum diagram of the fiber in Example 2 of the present invention recorded using a spectrometer. The recording result shows that no Raman peak is observed at the 1130 nm position.

[0115] Figure 10 This is the graph (aging curve) recording the relationship between the output power and time of the fiber in Example 2 of the present invention. The power drops by 1.2% after 500 hours.

[0116] Comparative Example 1

[0117] The core diameter of the fiber in Example 2 is changed to 39 microns, and the rest remains unchanged. The fiber laser output is tested using a MOPA amplification structure. After stripping the cladding light, the laser efficiency is 69%. As Figure 11 shown, it can be seen that when other conditions remain unchanged and the core diameter of the fiber is 39 microns, the laser efficiency of the obtained fiber is significantly lower than that of the fiber in Example 2. This is because as the core diameter increases, more high-order modes are generated in the fiber, resulting in part of the energy being more likely to be transmitted in the cladding and finally filtered out by the stripper, leading to a decrease in efficiency.

[0118] Comparative Example 2

[0119] The conditions of the collapsing step in Example 1 are controlled as follows:

[0120] Step 1: Burn hydrogen: 90 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 600 milliliters per minute of oxygen; torch moving speed: 55 millimeters per minute.

[0121] Step 2: Burn hydrogen: 94 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 600 milliliters per minute of oxygen; torch moving speed: 50 millimeters per minute.

[0122] Step 3: Burn hydrogen: 98 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 500 milliliters per minute of oxygen; torch moving speed: 45 millimeters per minute.

[0123] Step 4: Burn hydrogen: 102 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 500 milliliters per minute of oxygen; torch moving speed: 40 millimeters per minute.

[0124] Step 5: Burn hydrogen: 106 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 400 milliliters per minute of oxygen; torch moving speed: 35 millimeters per minute.

[0125] Step 6: Burn hydrogen: 110 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 400 milliliters per minute of oxygen; torch moving speed: 30 millimeters per minute.

[0126] Step 7: Burn hydrogen: 114 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 300 milliliters per minute of oxygen; torch moving speed: 25 millimeters per minute.

[0127] Step 8: Burn hydrogen: 122 liters per minute, hydrogen-oxygen combustion ratio: 1.8, gas in the tube: 100 milliliters per minute of oxygen; torch moving speed: 10 millimeters per minute.

[0128] Due to the change of the collapse process parameters, the refractive index profile of the optical fiber becomes a center-convex type (as Figure 12 ) Record the laser spectrogram with a spectrometer, and observe the Raman peak at the 1130 nm position (as Figure 13 ) It can be seen that when other conditions remain unchanged, when the collapse process parameters are changed, the refractive index profile of the obtained optical fiber changes from a flat type to a center-convex type. The center convexity causes the energy in the core center part to be more concentrated, and the high energy density leads to a more significant Raman effect.

[0129] Comparative Example 3

[0130] Change the core doping components in Example 1 to Yb2O3: 0.2 mol%, Al2O3: 2.1 mol%, P2O5: 1.8 mol%, and the rest is SiO2. The corresponding refractive index difference is 0.0022, and the aging power drops by 4% after 230 hours, as Figure 14As shown. It can be seen that the change in the doping components results in significantly worse fiber stability in Comparative Example 3 compared to that in Example 1. This is because P2O5 can keep ytterbium ions in the trivalent state, reducing the interference of defects on the valence state of ytterbium ions, thereby achieving better anti-photodarkening performance.

[0131] Comparative Example 4

[0132] In Example 1, the core doping components are Yb2O3: 0.4 mol%, Al2O3: 2 mol%, P2O5: 3.1 mol%, and the rest is SiO2; the corresponding refractive index difference is 0.0028. The beam quality parameter diagram is tested with PRIMES software, and its bpp value is 3.272, as Figure 15 shown. It can be seen that the change in the refractive index difference leads to an increase in the numerical aperture of the fiber, resulting in a deterioration of the laser beam quality.

[0133] In summary, for the ytterbium-doped high-power laser fibers prepared by the methods of the above Example 1 and Example 2, compared with the comparative examples, the doping components are more optimized, the core refractive index and the core diameter design are more reasonable, and the three of the doping components, the core refractive index, and the core diameter are more matched, enabling the fiber to still operate stably and efficiently at high powers above 6000 watts.

[0134] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

[0135] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A ytterbium-doped high-power laser fiber, characterized in that, The core diameter of the optical fiber is 32 - 36 microns, the cladding of the optical fiber is a regular octagon, and the face-to-face distance of the regular octagon is 440 - 470 microns; the doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, the concentration of Yb2O3 is 0.3 - 0.35 mol%, the doping concentration of aluminum element is calculated in the form of Al2O3, the concentration of Al2O3 is 1.9 - 2.2 mol%, the doping concentration of phosphorus element is calculated in the form of P2O5, the concentration of P2O5 is 2.8 - 3.5 mol%, and the rest is SiO2; the refractive index profile of the ytterbium-doped high-power laser optical fiber preform includes a collapsing step, and the collapsing step specifically includes eight steps, with the conditions controlled as follows: The first step: Combustion of hydrogen: 78 - 82 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 500 - 800 milliliters per minute of oxygen; torch moving speed: 55 millimeters per minute; The second step: Combustion of hydrogen: 82 - 86 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 500 - 800 milliliters per minute of oxygen; torch moving speed: 50 millimeters per minute; The third step: Combustion of hydrogen: 86 - 90 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 400 - 700 milliliters per minute of oxygen; torch moving speed: 45 millimeters per minute; The fourth step: Combustion of hydrogen: 90 - 94 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 400 - 700 milliliters per minute of oxygen; torch moving speed: 40 millimeters per minute; The fifth step: Combustion of hydrogen: 94 - 98 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 300 - 600 milliliters per minute of oxygen; torch moving speed: 35 millimeters per minute; The sixth step: Combustion of hydrogen: 98 - 102 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 300 - 600 milliliters per minute of oxygen; torch moving speed: 30 millimeters per minute; The seventh step: Combustion of hydrogen: 102 - 106 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 200 - 400 milliliters per minute of oxygen; torch moving speed: 25 millimeters per minute; The eighth step: Combustion of hydrogen: 110 - 114 liters per minute, combustion hydrogen-oxygen ratio: 2.0 - 2.3, gas in the tube: 100 - 200 milliliters per minute of oxygen; torch moving speed: 10 millimeters per minute.

2. A ytterbium-doped high-power laser fiber as described in claim 1, characterized in that, The core diameter of the optical fiber is 34 microns, the cladding of the optical fiber is a regular octagon, and the face-to-face distance of the regular octagon is 460 microns; the doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, the concentration of Yb2O3 is 0.32 mol%, the doping concentration of aluminum element is calculated in the form of Al2O3, the concentration of Al2O3 is 2 mol%, the doping concentration of phosphorus element is calculated in the form of P2O5, the concentration of P2O5 is 3.1 mol%, and the rest is SiO2; the refractive index profile of the laser optical fiber is flat.

3. A ytterbium-doped high-power laser fiber as claimed in claim 1, wherein, The core diameter of the optical fiber is 33 microns, the cladding of the optical fiber is a regular octagon, and the face-to-face distance of the regular octagon is 465 microns; the doping concentration of ytterbium element in the core is calculated in the form of Yb2O3, the concentration of Yb2O3 is 0.3 mol%, the doping concentration of aluminum element is calculated in the form of Al2O3, the concentration of Al2O3 is 2.1 mol%, the doping concentration of phosphorus element is calculated in the form of P2O5, the concentration of P2O5 is 3.2 mol%, and the rest is SiO2; the refractive index profile of the laser optical fiber is flat.

4. A method for preparing a ytterbium-doped high-power laser fiber preform, characterized in that, The ytterbium-doped high-power laser optical fiber preform as claimed in any one of claims 1-3 is prepared by the method for preparing the ytterbium-doped high-power laser optical fiber preform, including the steps of preparing a mother rod by using the MCVD method combined with the solution immersion method, and performing shape processing on the mother rod to obtain a ytterbium-doped high-power laser optical fiber preform with a regular octagon-shaped outer cladding and a core-cladding ratio meeting a preset ratio; the step of preparing the mother rod by using the MCVD method combined with the solution immersion method specifically includes: a loose body deposition step, a solution immersion step, a drying step, and a heat treatment step.

5. The method for preparing a ytterbium-doped high-power laser fiber preform according to claim 4, characterized in that, The conditions of the eight steps of the collapsing step are controlled as follows: The first step: Combustion hydrogen: 80 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 600 milliliters / minute of oxygen; Torch moving speed: 55 millimeters / minute; The second step: Combustion hydrogen: 84 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 600 milliliters / minute of oxygen; Torch moving speed: 50 millimeters / minute; The third step: Combustion hydrogen: 88 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 500 milliliters / minute of oxygen; Torch moving speed: 45 millimeters / minute; The fourth step: Combustion hydrogen: 92 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 500 milliliters / minute of oxygen; Torch moving speed: 40 millimeters / minute; The fifth step: Combustion hydrogen: 96 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 400 milliliters / minute of oxygen; Torch moving speed: 35 millimeters / minute; The sixth step: Combustion hydrogen: 100 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 400 milliliters / minute of oxygen; Torch moving speed: 30 millimeters / minute; The seventh step: Combustion hydrogen: 104 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 300 milliliters / minute of oxygen; Torch moving speed: 25 millimeters / minute; The eighth step: Combustion hydrogen: 112 liters / minute, combustion hydrogen-oxygen ratio: 2.2, gas in the tube: 100 milliliters / minute of oxygen; Torch moving speed: 10 millimeters / minute.

6. The method for preparing a ytterbium-doped high-power laser fiber preform according to claim 4, wherein, The conditions of the eight steps of the collapsing step are controlled as follows: The first step: Combustion hydrogen: 78 liters / minute, combustion hydrogen-oxygen ratio: 2.3, gas in the tube: 800 milliliters / minute of oxygen; Torch moving speed: 55 millimeters / minute; The second step: Combustion hydrogen: 82 liters / minute, combustion hydrogen-oxygen ratio: 2.3, gas in the tube: 800 milliliters / minute of oxygen; Torch moving speed: 50 millimeters / minute; Step 3: Burn hydrogen: 86 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 700 mL / min of oxygen; torch moving speed: 45 mm / min; Step 4: Burn hydrogen: 90 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 700 mL / min of oxygen; torch moving speed: 40 mm / min; Step 5: Burn hydrogen: 94 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 600 mL / min of oxygen; torch moving speed: 35 mm / min; Step 6: Burn hydrogen: 98 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 600 mL / min of oxygen; torch moving speed: 30 mm / min; Step 7: Burn hydrogen: 102 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 400 mL / min of oxygen; torch moving speed: 25 mm / min; Step 8: Burn hydrogen: 110 L / min, hydrogen-oxygen combustion ratio: 2.3, gas in the tube: 200 mL / min of oxygen; torch moving speed: 10 mm / min.

7. A ytterbium-doped high-power laser fiber preform, characterized in that, The preform is prepared by the method for preparing a ytterbium-doped high-power laser fiber preform as described in any one of claims 4-6.

8. A method for preparing a ytterbium-doped high-power laser fiber, characterized in that, The ytterbium-doped high-power laser fiber preform prepared by the method as described in any one of claims 4 to 6 is drawn to obtain the ytterbium-doped high-power laser fiber.

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