Pumping fiber combiner with high return light bearing capacity

Abstract

The utility model provides a pumping optical fiber combiner with high return light bearing capacity, which comprises a quartz tube, a plurality of pumping optical fibers, a signal optical fiber and an output optical fiber, a plurality of pumping bare fiber parts and a plurality of signal bare fiber parts are combined into a bundle and penetrate into the quartz tube, and the plurality of pumping bare fiber parts and the signal bare fiber parts form tapering parts through fused tapering. The tapering part is welded with the output optical fiber after the end face is flatly cut, a light guide groove is formed in the peripheral wall of the quartz tube through laser etching, the light guide groove and the tapering part are located at the two opposite ends in the light path direction, and the multiple pumping bare fiber parts are adjacent to the inner peripheral wall of the mounting hole. According to the scheme, the laser is used for etching one or more light guide grooves in the quartz tube, so that the transmission path of return light in the quartz tube is destroyed, the return light gradually leaks to the metal packaging box from the light guide grooves and is finally converted into heat to be released, the return light bearing capacity of the pumping optical fiber beam combiner is improved, and the service life of the pumping optical fiber beam combiner is prolonged. And the output performance of the pumping fiber combiner is also improved.

Description

Technical Field

[0001] The utility model relates to the field of optical devices, in particular to a pump optical fiber combiner with high return light bearing capacity. Background Art

[0002] At present, the power of a single oscillator cavity of a high-power fiber laser is getting higher and higher. In order to achieve higher power output, single forward pumping cannot meet the power requirements. Therefore, the pumping method of high-power laser oscillators generally adopts forward and reverse bidirectional end-face pumping. In a bidirectionally pumped laser system, the core signal light lost at the fusion point and the unabsorbed pump light in the gain fiber will be transmitted to the pump fiber combiner. Therefore, the pump fiber combiner needs to have a certain return light processing capability.

[0003] There are two main ways to make high-power pump fiber combiners, namely the knotting method and the sleeve method. The high-power pump fiber combiner made by the sleeve method is to insert a fiber bundle composed of multiple optical fibers into a quartz tube, heat it in a hydrogen-oxygen flame or high-temperature graphite filament, melt and pull it into a cone shape, and then cut and fuse it with a single output fiber to make a fiber combiner. This method is a relatively common production method. Since this method keeps the optical fiber straight in the quartz tube and the clean optical fiber is not in direct contact with the outside world, it can ensure excellent beam quality and withstand high-power pump light. However, for the combiner made by the sleeve method, due to the influence of the outer quartz tube, the return light in the optical path will leak out more from the fusion point and be transmitted along the quartz tube to the coating position at the end of the fiber bundle. The material of the conventional optical fiber coating is acrylate, and the maximum temperature is about 100°C. When there is more return light at the coating position, the temperature at this position will rise, and the device is at risk of burning.

[0004] The beam combiner made by the knotting method does not require a quartz tube, and the amount of return light leaking to the fiber bundle coating is less, and the return light tolerance is stronger than that of the tube method. Therefore, a reliable technical solution is needed to solve the shortcomings of the tube method fiber beam combiner's weak return light tolerance, and give full play to the technical advantages of the tube method beam combiner, which has good beam quality, high power tolerance, and low core light loss, which is conducive to the long-term stable operation of the laser system. Utility Model Content

[0005] The utility model aims to provide a pump optical fiber combiner with high return light bearing capacity.

[0006] In order to achieve the purpose of the utility model, the utility model provides a pump fiber combiner with high return light tolerance, including a quartz tube, a plurality of pump fibers, a signal fiber and an output fiber, the quartz tube, the plurality of pump fibers and the signal fiber all extend along the optical path direction, and the quartz tube is penetrated with a mounting hole along the optical path direction; after removing the coating layer of the plurality of pump fibers, a pump bare fiber portion is formed, and after removing the coating layer of the signal fiber, a signal bare fiber portion is formed, and the plurality of pump bare fiber portions are adjacently arranged on the radial periphery of the signal bare fiber, the plurality of pump bare fiber portions and the signal bare fiber portions are bundled and inserted into the mounting hole, the plurality of pump bare fiber portions and the signal bare fiber portions are melt-tapered to form a tapered portion, and the tapered portion is fused with the output optical fiber after the end face is cut flat; the outer peripheral wall of the quartz tube is etched by a carbon dioxide laser to form a light guide groove, the light guide groove and the tapered portion are located at opposite ends in the optical path direction, and the plurality of pump bare fiber portions are adjacent to the inner peripheral wall of the mounting hole.

[0007] A further solution is that the light guide groove extends in a ring shape around the center line of the quartz tube.

[0008] A further solution is that the transverse base surface of the light guide groove is arranged in a U shape.

[0009] A further solution is that the outer peripheral wall of the quartz tube has a plurality of light guiding grooves, and the plurality of light guiding grooves are arranged along the light path direction.

[0010] A further solution is that the signal optical fiber is a double-clad optical fiber.

[0011] A further solution is that the output optical fiber is a double-clad optical fiber.

[0012] A further solution is that the pump fiber combiner includes a metal packaging box, and the quartz tube is arranged in the metal packaging box.

[0013] A further solution is that the pump fiber combiner includes a quartz substrate, the quartz tube is arranged on the quartz substrate, and the quartz substrate is arranged in a metal packaging box.

[0014] The beneficial effect of the utility model is that after removing the coating layer, the pump bare fiber part and the signal bare fiber part can be inserted into the mounting hole from one side of the light guide groove, and then multiple pump bare fiber parts and signal bare fiber parts are formed into a tapered part through melting and tapering, and then the tapered part is cut flat on the end face and fused with the output optical fiber to form a pump fiber combiner. Since the outer wall of the quartz tube is etched by a carbon dioxide laser to form a light guide groove, and the light guide groove and the tapered part are located at two opposite ends of the optical path direction, the carbon dioxide laser is used to etch one or more light guide grooves on the quartz tube by utilizing the high absorption efficiency of quartz glass to the wavelength of carbon dioxide laser, thereby destroying the transmission path of the return light in the quartz tube, and gradually leaking the return light from the light guide groove to the metal packaging box, and finally converting it into heat and releasing it out, thereby improving the return light bearing capacity of the pump fiber combiner and also improving the output performance of the pump fiber combiner. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of a quartz tube in an embodiment of the pump fiber combiner of the utility model.

[0016] Figure 2 It is a structural diagram of the pump optical fiber in the embodiment of the pump optical fiber combiner of the utility model.

[0017] Figure 3 It is a structural diagram of the pump fiber combiner embodiment of the utility model after the pump bare fiber part and the signal bare fiber part are inserted into the quartz tube.

[0018] Figure 4 It is a structural diagram of the pump fiber combiner embodiment of the utility model after taper fusion.

[0019] Figure 5 This is a schematic diagram of the optical fiber distribution of an embodiment of the pump optical fiber combiner of the utility model.

[0020] Figure 6 It is a schematic diagram of filtering the return light of the pump fiber combiner embodiment of the utility model.

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0022] Reference Figures 1 to 6 The pump fiber combiner includes a quartz tube 1, a plurality of pump fibers 21, a signal fiber 22 and an output fiber 3. The quartz tube 1, the plurality of pump fibers 21 and the signal fiber 22 all extend along the optical path direction X. In this embodiment, the pump fiber combiner adopts a (6+1)×1 combiner arrangement scheme. The pump fiber combiner includes six pump fibers 21. The inner and outer diameters of the quartz tube selected in this embodiment are 400 / 500um. The pump fiber 21 uses a 220 / 242um (0.22NA) optical fiber, the signal fiber 22 uses a 25 / 250um (0.065 / 0.46NA) double-clad optical fiber, and the output fiber 3 uses a 20 / 400um (0.65 / 0.46NA) double-clad optical fiber.

[0023] When manufacturing a pump fiber combiner, the steps are as follows:

[0024] Step 1, first pre-treat the quartz tube 1, select a 100 mm long quartz tube 1, the quartz tube 1 is provided with a mounting hole 11 along the optical path direction X, wipe its surface with alcohol, and use a carbon dioxide laser to etch a plurality of light guide grooves 12 on the outer peripheral wall of the quartz tube 1 near the tube opening at one end of the optical fiber bundle. The plurality of light guide grooves 12 are arranged along the optical path direction X, and the light guide grooves 12 extend in a ring shape around the center line of the quartz tube 1, and the transverse base surface of the light guide grooves 12 is arranged in a U shape. In addition to this embodiment, the light guide grooves can be set in different shapes, distributions, and quantities on the quartz tube to achieve the effect of filtering out the return light.

[0025] Step 2, then prepare the pump fiber, the redundant space between the fiber bundle and the inner diameter of the quartz tube is set to 10um, the number of fiber bundle fiber distribution layers is 3, and the pre-processed diameter can be calculated according to the following formula:

[0026] ;

[0027] Where d1 represents the core diameter of the signal fiber, d0 represents the core diameter of the output fiber, D0 represents the cladding diameter of the output fiber, k represents the ratio of the outer diameter to the inner diameter of the quartz tube, a represents the redundant space between the fiber bundle diameter and the inner diameter of the quartz tube, which is generally 10-15um, and n represents the number of distribution layers of the fiber bundle.

[0028] Through the above calculation, it is concluded that the pre-treated diameter of the pump fiber is 130um. The surface coating 211 of 6 220 / 242um pump optical fibers 21 is removed from the tail of one end to form a pump bare fiber part 212. The length of 100-120mm is removed, and the surface is cleaned with high-concentration alcohol. They are placed on a graphite taper machine and drawn into double-tapered optical fibers 213 with a waist diameter of 130um. The taper at one end of the optical fiber bundle is retained, and the taper on one side of the short fiber is cut off at the taper waist boundary.

[0029] Step 3, prepare the signal optical fiber 22. The pre-processed diameter of the signal optical fiber 22 is generally 2-3um smaller than the pre-processed diameter of the pump fiber. After removing the coating layer from the tail of one end of the signal optical fiber 22 to form a signal bare fiber part, a certain concentration of hydrofluoric acid is used to corrode the optical fiber cladding diameter from 250um to 127-128um, which is slightly smaller than the pump fiber.

[0030] Step 4, bundle and pass through the tube, place the signal optical fiber 22 in the middle of the six pump optical fibers 21, and arrange multiple pump bare fiber parts 212 adjacent to the radial periphery of the signal bare fiber, and penetrate from the quartz tube 1 with one end of the light guide groove 12. The diameter of the fiber bundle composed of the signal optical fiber 22 and the pump optical fiber 21 is 387-388um, which is slightly smaller than the inner diameter of the quartz tube 1 of 400um, so it is convenient to penetrate into the quartz tube 1 and fix it. Multiple pump bare fiber parts 212 are adjacent to the inner wall of the mounting hole 11, and the pump bare fiber part 212 is located on the inner side of the light guide groove 12.

[0031] Step 5, draw the optical fiber bundle, put the prepared optical fiber bundle and quartz tube into a graphite taper machine for drawing, and form a taper portion 14 through melt taper of multiple pump bare fiber parts 212 and signal bare fiber parts, and the diameter of the optical fiber bundle is thinned from 500um to 390-400um. At this time, the taper ratio of the optical fiber bundle is 500 / 400=1.25. During the taper process, the fiber bundle changes proportionally, and the core of the signal optical fiber 25 / 250um in the fiber bundle becomes 25 / 1.25=20um, and the core diameter is consistent with the core of the output optical fiber 3.

[0032] Step 5, cutting and welding, cutting the drawn optical fiber bundle at the position of 390-400um diameter, that is, flattening the end face of the tapered portion 14, and welding the end face with the output optical fiber 3, monitoring the welding loss in real time during the welding process, and then the light guide groove 12 and the tapered portion 14 are located at opposite ends of the optical path direction X.

[0033] Step 6: Package the welded product and fix it on the quartz substrate using UV glue with high transmittance and low expansion coefficient, so that the product can maintain reliable performance in different usage environments. Then fix the quartz substrate in the metal packaging box using UV glue.

[0034] Reference Figure 6 As shown by the arrow in the figure, the return light in the laser system passes through the pump combiner and continues to be transmitted to the end of the optical fiber bundle along the quartz tube 1 at the fusion point. Due to the existence of the light guide groove 12, the transmission path of the return light is destroyed. The return light leaks out at the position of the light guide groove 12 and can leak onto the metal packaging box, thereby achieving the effect of filtering out the return light.

[0035] As can be seen from the above, since the outer wall of the quartz tube is etched by a carbon dioxide laser to form a light guide groove, and the light guide groove and the tapered portion are located at two opposite ends of the optical path direction, the carbon dioxide laser is used to etch one or more light guide grooves on the quartz tube using the high absorption efficiency of quartz glass to the wavelength of carbon dioxide laser, thereby destroying the transmission path of the return light in the quartz tube, and gradually leaking the return light from the light guide groove to the metal packaging box, and finally converting it into heat and releasing it, thereby improving the return light bearing capacity of the pump fiber combiner and also improving the output performance of the pump fiber combiner.

Claims

1. A pump fiber combiner with high return light tolerance, comprising a quartz tube, a plurality of pump fibers, a signal fiber and an output fiber, wherein the quartz tube, the plurality of pump fibers and the signal fiber all extend along an optical path, and the quartz tube is provided with a mounting hole through the optical path; Features: After removing the coating layers of the plurality of pump optical fibers, a pump bare fiber portion is formed; after removing the coating layers of the signal optical fibers, a signal bare fiber portion is formed; the plurality of pump bare fiber portions are adjacently arranged on the radial periphery of the signal bare fiber; the plurality of pump bare fiber portions and the signal bare fiber portions are bundled and inserted into the mounting hole; the plurality of pump bare fiber portions and the signal bare fiber portions are melt-tapered to form a tapered portion; the tapered portion is fused with the output optical fiber after the end face is cut flat; The outer peripheral wall of the quartz tube is etched by a carbon dioxide laser to form a light guide groove, the light guide groove and the tapered portion are located at two opposite ends of the optical path, and a plurality of the pump bare fiber portions are adjacent to the inner peripheral wall of the mounting hole.

2. The pump fiber combiner according to claim 1, characterized in that: The light guide groove extends in a ring shape around the center line of the quartz tube.

3. The pump fiber combiner according to claim 2, characterized in that: The transverse base surface of the light guide groove is arranged in a U shape.

4. The pump fiber combiner according to claim 2, characterized in that: The outer peripheral wall of the quartz tube has a plurality of light guide grooves, and the plurality of light guide grooves are arranged along the direction of the light path.

5. The pump fiber combiner according to any one of claims 1 to 4, characterized in that: The signal optical fiber is a double-clad optical fiber.

6. The pump fiber combiner according to any one of claims 1 to 4, characterized in that: The output optical fiber is a double-clad optical fiber.

7. The pump fiber combiner according to any one of claims 1 to 4, characterized in that: The pump fiber combiner comprises a metal packaging box, and the quartz tube is arranged in the metal packaging box.

8. The pump fiber combiner according to claim 7, characterized in that: The pump fiber combiner comprises a quartz substrate, the quartz tube is arranged on the quartz substrate, and the quartz substrate is arranged in the metal packaging box.

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