CN110429464A - A high power laser beam combiner - Google Patents

Abstract

The invention discloses a high-power laser beam combiner, which belongs to the field of lasers and comprises a laser generating unit and a sensing module; the laser generation unit is used for welding optical fibers output by the plurality of LD modules on the beam combiner, and selecting a proper tapering ratio and a proper cutting angle by preprocessing the quartz glass tube and the optical fibers, so that tapering loss is reduced, the uniformity of a welding point is improved, bubbles are reduced, the precision of optical fiber beam combination processing is improved, the output power of the optical fiber beam combiner is improved, and the stability of a device is improved; the sensing module comprises multiple monitoring of power acquisition, temperature, humidity, scattering PD and transmission open circuit, the sensor module is positioned inside the LD module and carries out multiple monitoring based on the ARM and the FPGA module, the spatial resolution of the system is ensured under high-speed acquisition, and meanwhile, the signal can be processed in real time to improve the signal-to-noise ratio of the signal.

Description

A high power laser beam combiner

technical field

The invention belongs to the field of lasers, in particular to a high-power laser beam combiner.

Background technique

Fiber laser has the advantages of high conversion efficiency, good beam quality, compact structure and convenient maintenance. It has been widely used in scientific research, industrial manufacturing, national defense security and other fields. With the development of technology, the output power of fiber laser has been continuously improved. At present, the output power of a single single-mode fiber laser has reached 10,000 watts, and there is a certain room for improvement. However, due to thermal damage, nonlinear effects, fiber end face damage, thermal lens effect, etc. Restricted by factors, the output power of a single single-mode fiber laser cannot be increased infinitely, so it is necessary to increase the output power of the fiber laser through synthesis technology.

Laser beam combining is an effective means to greatly increase laser output power and radiance. It mainly combines multiple laser beams into one output beam. At present, laser beam combining methods include spatial coupling method and optical fiber beam combining method. The spatial coupling method uses solid-state optics The device couples light into the optical fiber, and uses a lens with high transparency to the pump light and high reflection to the signal light to couple the pump light and the signal light into the double-clad fiber to realize the amplification of the signal light. The efficiency of the spatial coupling method is relatively low , only about 60%-70%, and the use of solid lens combination has poor stability; the fiber combining method is to prepare a fiber combiner on the basis of melting the tapered fiber bundle, and the fiber combiner is a high-power fiber laser One of the most important devices, it plays a pivotal role in the future development of high-power fiber lasers. It is a passive device that enables directional transmission of power and plays an important role in high-power all-fiber lasers. Fiber combiners It has the advantages of high coupling efficiency, convenient operation, easy realization of full fiber, suitable for use under high power, etc.

At present, the preparation process of optical fiber combiner is mainly divided into rotation method and sleeve method. The rotation method winds multiple optical fiber bundles, heats the tapered fibers to fuse them together, and makes optical fiber bundles, which are cut at the thinner fiber bundles. And it is fused with the output fiber to make a fiber combiner, but the power of the fiber combiner prepared by this method is not high; the sleeve method is to pass multiple optical fibers into the quartz sleeve, and then heat the tapered sleeve to make the sleeve It is fused together with the optical fiber, and then cut and fused with the output optical fiber. The fiber combiner prepared by the sleeve method has a greater advantage in output power, but the technical requirements for the sleeve taper are higher, and the processing accuracy is higher. Improper operation can easily cause damage to the structure of the optical fiber.

China Patent Authorization Announcement No. CN201621024211.X, the name of the invention is a mid-infrared band optical fiber pumping/signal combiner, the core material of the signal optical fiber used in this invention is pure germanium dioxide material, and the tapered region of the optical fiber bundle The taper ratio is between 1 and 3, and the fiber bundle is fused with the output fiber. Although this method can couple high-power lasers into the output fiber, its disadvantage is that the range of the taper ratio is large, and the signal fiber is here The loss in the ratio range of the tapering is larger.

Contents of the invention

Aiming at the problems of low coupling efficiency, poor stability, and high requirements for operating process precision in traditional fiber optic beam combiners, the present invention provides a high-power laser beam combiner, which replaces the spatial coupling beam combining method with optical fiber beam combining, and Quartz glass tubes and optical fibers are pretreated, and the appropriate taper ratio and cutting angle are selected to reduce the taper loss, improve the precision of fiber combining processing, and increase the output power of the fiber combiner. At the same time, it is based on ARM and FPGA modules. Multiple monitoring of power collection, temperature, humidity, scattered PD, and transmission disconnection.

A high-power laser beam combiner, including a laser generating unit and a sensing module; wherein the laser generating unit fuses the optical fibers output by multiple LD modules to the beam combiner, and the sensing module includes power collection, temperature, humidity, and scattering Multiple monitoring of PD, transmission break, and the sensor module is located inside the LD module.

Further, the beam combiner includes a plurality of input fibers and an output fiber, the number of input fibers is consistent with the number of fiber lasers, and one end of the plurality of input fibers is respectively fused with output signal fibers of a plurality of fiber laser modules, After the other end is fused and tapered, the truncated cone area is fused with one end of the output fiber.

Further, the preparation method of the beam combiner comprises the following steps:

(1) Glass tube preparation: prepare a quartz glass tube, use diamond to smooth the end of the glass sleeve, and perform ultrasonic cleaning after smoothing;

(2) The first tapering of the glass tube: Taper the glass tube for the first time, so that the inner diameter of the glass sleeve is slightly larger than the diameter of the optical fiber bundle;

(3) Optical fiber treatment: remove the coating from one end of the input optical fiber, and fix the other end with adhesive tape;

(4) Penetrating the optical fiber: slowly insert the bare fiber part of the optical fiber into the glass sleeve under the action of alcohol lubrication from the end close to the short tapered area;

(5) Secondary taper of optical fiber bundle: the second taper of optical fiber bundle and glass tube together;

(6) Optical fiber bundle cutting and welding: heat the outside of the quartz glass tube at a temperature of 1700°C to fuse the quartz glass tube, input optical fiber, and quartz glass tube into one, cut it with an optical fiber cutter, and combine it with a Splicing of large core diameter conductive optical fiber;

(7) Heat sealing: Use an outer sealing tube to protect the weld joint.

Further, the quartz glass tube in the step (1) is a fluorine-doped quartz tube.

When tapering the glass tube, the higher the temperature of the molten state, the smaller the viscosity of the glass tube. Even under the same premise of the tapering speed, the thinner part of the glass tube is easy to deform, resulting in The glass tube is not a perfect circle, which affects the stability of the beam combiner, and the glass tube of the fluorine-doped quartz tube reduces the error, so it can reduce the instability of the beam combiner caused by deformation.

Further, after the optical fiber in the step (4) is threaded, the residual alcohol in the glass tube needs to be cleaned before being tapered.

Since the alcohol is not cleaned, in the high-temperature melting state, the alcohol volatilizes and causes the inner wall of the glass tube to burn black. Therefore, a vacuum pump is used in the experiment to deal with the residual alcohol in the glass tube to avoid the inner wall of the glass tube being burnt black due to alcohol volatilization.

Further, in the step (4), after the optical fiber bundle penetrates into the glass tube, the optical fiber bundle is fine-tuned through a microscope.

Since the optical fiber bundles are inserted into the glass tube, there will be stress and crossing between the optical fibers, resulting in uneven distribution of the optical fiber bundles in the glass tube. Ensure that the bare optical fiber of each optical fiber penetrates into the tapered area of the quartz glass tube to ensure that there is no stress in the optical fiber, no coils, and the arrangement is uniform in the glass tube to realize the tapering of the optical fiber bundle.

Further, in the step (5), the length of the tapered input fiber in the experiment is set to 13 mm, and the tapered ratio is set to 1.3.

Among them, the cladding and core of the optical fiber gradually decrease with the tapering process. When the core is reduced, the light transmitted in the core enters the cladding, reducing the tapering loss and improving the stability of the device.

Further, the cutting angle of the optical fiber bundle in the step (6) is controlled within 0.5 degrees.

During the fiber bundle cutting process, if the cutting angle is too large, it will easily cause uneven fusion points and bubbles. When the cutting angle is small, the uniformity of fusion points can be improved, the generation of bubbles can be reduced, and the stability of the device can be improved.

Further, in the step (6), the outer side of the quartz glass tube is heated by a three-electrode ring fire method.

The three-electrode ring fire method is used to heat the fiber bundle evenly, the cone of the fiber bundle out of the taper changes uniformly, and the electrodes are not easy to damage and oxidize, the service life is relatively long, and the cost is saved. Compared with the hydrogen-oxygen flame heating the taper , no need to control the gas flow rate, safe operation.

Further, the sensing module is based on ARM and FPGA modules for multiple monitoring.

Because the ARM processor has the advantages of fixed instruction length, better performance, and lower cost, in the present invention, the ARM processor is mainly responsible for two functions: receiving configuration information from the client and controlling the flow of the sensor system, Process and calculate the power, temperature, humidity, scattered PD, and transmission disconnection data obtained by the sensor; the FPGA module is used to analyze and calculate the data transmitted by the ARM. Spatial resolution, and at the same time, it can process the signal in real time to improve the signal-to-noise ratio of the signal.

The working principle of the present invention: superimpose the radiation power by adopting incoherent beam combining, adopt the optical fiber beam combining method to prepare the optical fiber beam combiner on the basis of melting the tapered fiber bundle, and prepare the optical fiber beam combiner by using the sleeve method The fluorine-doped quartz tube is used in the process to reduce the instability of the beam combiner caused by the deformation during the tapering process; the fiber bundle is fine-tuned through a microscope to ensure that there is no stress in the fiber, no coils, and the arrangement is uniform in the glass tube, realizing the fiber The taper of the beam; setting the appropriate taper ratio and cutting angle reduces the loss of the taper, improves the uniformity of the welding point, reduces the generation of air bubbles, and improves the stability of the device.

Beneficial effect

(1) The present invention adopts the optical fiber beam combining method instead of the space coupling beam combining method, pre-treats the quartz glass tube and the optical fiber, selects the appropriate tapering ratio and cutting angle, reduces the tapering loss, and improves the processing efficiency of the optical fiber beam combining. Accuracy, improve the output power of the fiber combiner, and perform multiple monitoring of power collection, temperature, humidity, scattering PD, and transmission disconnection based on ARM and FPGA modules.

(2) In the present invention, the optical fiber stripping is carried out by thermal stripping, which reduces the damage on the surface of the optical fiber cladding and improves the stability of the beam combiner compared with mechanical stripping and chemical stripping.

(3) The present invention uses a three-electrode ring fire method for heating, so that the optical fiber bundles are heated evenly, and the cones of the optical fiber bundles produced by the taper change uniformly, and the electrodes are not easy to be damaged and oxidized, and the service life is relatively long, saving costs. The bicone is heated by an oxyhydrogen flame, no need to control the gas flow rate, and the operation is safe.

(4) In the experiment of the present invention, an appropriate tapering ratio is set, which reduces the tapering loss during the tapering process of the optical fiber bundle and the glass tube, and improves the stability of the device.

(5) The cutting angle of the optical fiber bundle of the present invention is controlled within 0.5 degrees. During the cutting process of the optical fiber bundle, if the cutting angle is too large, it will easily cause unevenness of the fusion splicing point, and bubbles will be generated. When the cutting angle is small, the uniformity of the fusion splicing point can be improved. Sex, reduce the generation of air bubbles, and then improve the stability of the device.

Description of drawings

Figure 1 is the optical circuit diagram of the single-arm output power test of the 7×1 beam combiner;

Figure 2 is the optical circuit diagram of the single-arm input power test of the 7×1 beam combiner.

Detailed ways

The technical solutions of the various embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them; based on the embodiments of the present invention, All other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1

A high-power laser beam combiner, including a laser generating unit and a sensing module; wherein the laser generating unit fuses the optical fibers output by multiple LD modules to the beam combiner, and the sensing module includes power collection, temperature, humidity, and scattering Multiple monitoring of PD, transmission break, and the sensor module is located inside the LD module.

Further, the beam combiner includes a plurality of input fibers and an output fiber, the number of input fibers is consistent with the number of fiber lasers, and one end of the plurality of input fibers is respectively fused with output signal fibers of a plurality of fiber laser modules, After the other end is fused and tapered, the truncated cone area is fused with one end of the output fiber.

Further, the preparation method of the beam combiner comprises the following steps:

(1) Glass tube preparation: prepare a quartz glass tube, use diamond to smooth the end of the glass sleeve, and perform ultrasonic cleaning after smoothing;

(2) The first tapering of the glass tube: Taper the glass tube for the first time, so that the inner diameter of the glass sleeve is slightly larger than the diameter of the optical fiber bundle;

(3) Optical fiber treatment: remove the coating from one end of the input optical fiber, and fix the other end with adhesive tape;

(4) Penetrating the optical fiber: slowly insert the bare fiber part of the optical fiber into the glass sleeve under the action of alcohol lubrication from the end close to the short tapered area;

(5) Secondary taper of optical fiber bundle: the second taper of optical fiber bundle and glass tube together;

(6) Optical fiber bundle cutting and welding: heat the outside of the quartz glass tube at a temperature of 1700°C to fuse the quartz glass tube, input optical fiber, and quartz glass tube into one, cut it with an optical fiber cutter, and combine it with a Splicing of large core diameter conductive optical fiber;

(7) Heat sealing: Use an outer sealing tube to protect the weld joint.

Further, the quartz glass tube in the step (1) is a fluorine-doped quartz tube.

When tapering the glass tube, the higher the temperature of the molten state, the smaller the viscosity of the glass tube. Even under the same premise of the tapering speed, the thinner part of the glass tube is easy to deform, resulting in The glass tube is not a perfect circle, which affects the stability of the beam combiner, and the glass tube of the fluorine-doped quartz tube reduces the error, so it can reduce the instability of the beam combiner caused by deformation.

Further, after the optical fiber in the step (4) is threaded, the residual alcohol in the glass tube needs to be cleaned before being tapered.

Since the alcohol is not cleaned, in the high-temperature melting state, the alcohol volatilizes and causes the inner wall of the glass tube to burn black. Therefore, a vacuum pump is used in the experiment to deal with the residual alcohol in the glass tube to avoid the inner wall of the glass tube being burnt black due to alcohol volatilization.

Further, in the step (4), after the optical fiber bundle penetrates into the glass tube, the optical fiber bundle is fine-tuned through a microscope.

Since the optical fiber bundles are inserted into the glass tube, there will be stress and crossing between the optical fibers, resulting in uneven distribution of the optical fiber bundles in the glass tube. Ensure that the bare optical fiber of each optical fiber penetrates into the tapered area of the quartz glass tube to ensure that there is no stress in the optical fiber, no coils, and the arrangement is uniform in the glass tube to realize the tapering of the optical fiber bundle.

Further, in the step (5), the length of the tapered input fiber in the experiment is set to 13 mm, and the tapered ratio is set to 1.3.

Among them, the cladding and core of the optical fiber gradually decrease with the tapering process. When the core is reduced, the light transmitted in the core enters the cladding, reducing the tapering loss and improving the stability of the device.

Further, the cutting angle of the optical fiber bundle in the step (6) is controlled within 0.5 degrees.

During the fiber bundle cutting process, if the cutting angle is too large, it will easily cause uneven fusion points and bubbles. When the cutting angle is small, the uniformity of fusion points can be improved, the generation of bubbles can be reduced, and the stability of the device can be improved.

Further, in the step (6), the outer side of the quartz glass tube is heated by a three-electrode ring fire method.

The three-electrode ring fire method is used to heat the fiber bundle evenly, the cone of the fiber bundle out of the taper changes uniformly, and the electrodes are not easy to damage and oxidize, the service life is relatively long, and the cost is saved. Compared with the hydrogen-oxygen flame heating the taper , no need to control the gas flow rate, safe operation.

Further, the sensing module is based on ARM and FPGA modules for multiple monitoring.

Because the ARM processor has the advantages of fixed instruction length, better performance, and lower cost, in the present invention, the ARM processor is mainly responsible for two functions: receiving configuration information from the client and controlling the flow of the sensor system, Process and calculate the power, temperature, humidity, scattered PD, and transmission disconnection data obtained by the sensor; the FPGA module is used to analyze and calculate the data transmitted by the ARM. Spatial resolution, and at the same time, it can process the signal in real time to improve the signal-to-noise ratio of the signal.

Example 2

On the basis of Example 1, the glass tube used in this example is a low-refractive-index fluorine-doped glass tube with a core numerical aperture of 0.22. The input optical fiber is a 20/250um optical fiber with a core numerical aperture of 0.06. The optical fiber is a 20/400um high-power energy-transfer optical fiber with a core numerical aperture of 0.22, a tapered ratio of 1.3, and a tapered length of 13mm. A 7×1 fiber combiner is prepared.

The withstand power test of the 7×1 fiber combiner is shown in Figure 1. Figure 1 is the optical circuit diagram of the single-arm output power test of the 7×1 beam combiner. The 7 single-arm optical fibers of the type beam combiner are fused, and a zero-degree angle is cut at the end of the output optical fiber, and the power meter is aligned with the outgoing spot. During the test, record the output power corresponding to the nth optical fiber when the corresponding DL is loaded with a certain current. P _n , after completing the above tests, conduct a single-arm input power test, as shown in Figure 2, Figure 2 is a 7×1 beam combiner single-arm input power test optical circuit diagram, the fusion point between DL and each arm is reserved, and the combined One section is subtracted from the single arm of the beamer, and the optical path test is carried out. The initial power value P _n ^/ of the nth optical fiber when the corresponding DL is loaded with the same current, and the transmission efficiency η _n of the nth optical fiber, η _n= P _n /P _n ^/ , coupling loss L _i =-10log(η _n )db, it can be obtained that the output power of the beam combiner is 1634w, the average coupling efficiency of the beam combiner is 99.1%, and the coupling loss is 0.03db.

Comparative example 1

On the basis of Example 1, the glass tube used in this example is a low-refractive-index fluorine-doped glass tube with a core numerical aperture of 0.22. The input optical fiber is a 20/250um optical fiber with a core numerical aperture of 0.06. The optical fiber is a 20/400um high-power energy-transfer optical fiber with a core numerical aperture of 0.22, a tapered ratio of 2, and a tapered length of 20mm. A 7×1 fiber combiner is prepared.

The withstand power test of the 7×1 fiber combiner shows that the output power of the combiner is 1075w, the average coupling efficiency of the combiner is 65.1%, and the coupling loss is 1.86db.

From the results of Example 2 and Comparative Example 1, it can be seen that when the ratio of the taper is larger and the length of the taper is longer, the transmission efficiency of the beam combiner is reduced. This is mainly because, when the ratio of the taper and the length of the taper When it is unreasonable, it will lead to the unevenness of the tapered area, which will lead to a decrease in the transmission efficiency of the cone. When the ratio of the tapered is large and the length of the tapered is long, the unevenness of the tapered area is serious. The transmission efficiency is only 65.1%. When the ratio of the taper is 1.3, the length of the taper is 13mm, the transition area of the taper is smooth, and the transmission efficiency of the cone is 99.1%. Therefore, when the ratio of the taper is 1.3, the length of the taper is 13mm, the transmission efficiency of the cone is higher.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (10)

1. A high-power laser beam combiner is characterized in that it comprises a laser generating unit and a sensing module; wherein the laser generating unit is fused on the beam combiner by the optical fibers output by a plurality of LD modules, and the sensing module includes a power acquisition , temperature, humidity, scattering PD, multiple monitoring of transmission break, and the sensor module is located inside the LD module. 2. a kind of high power laser beam combiner according to claim 1, is characterized in that, described beam combiner comprises a plurality of input optical fibers and an output optical fiber, the quantity of input optical fiber is consistent with the quantity of fiber laser, so One end of the plurality of input fibers is respectively fused with the output signal fibers of the plurality of fiber laser modules, and the other end is fused and tapered, and the truncated tapered region is fused with one end of the output fiber. 3. a kind of high-power laser beam combiner according to claim 1 or 2, is characterized in that, the preparation method of described beam combiner, comprises the following steps: (1) Glass tube preparation: prepare a quartz glass tube, use diamond to smooth the end of the glass sleeve, and perform ultrasonic cleaning after smoothing; (2) The first tapering of the glass tube: Taper the glass tube for the first time, so that the inner diameter of the glass sleeve is slightly larger than the diameter of the optical fiber bundle; (3) Optical fiber treatment: remove the coating from one end of the input optical fiber, and fix the other end with adhesive tape; (4) Penetrating the optical fiber: slowly insert the bare fiber part of the optical fiber into the glass sleeve under the action of alcohol lubrication from the end close to the short tapered area; (5) Secondary taper of optical fiber bundle: the second taper of optical fiber bundle and glass tube together; (6) Optical fiber bundle cutting and welding: heat the outside of the quartz glass tube at a temperature of 1700°C to fuse the quartz glass tube, input optical fiber, and quartz glass tube into one, cut it with an optical fiber cutter, and combine it with a Splicing of large core diameter conductive optical fiber; (7) Heat sealing: Use an outer sealing tube to protect the weld joint. 4. A high-power laser beam combiner according to claim 3, characterized in that the quartz glass tube in the step (1) is a fluorine-doped quartz tube. 5. A high-power laser beam combiner according to claim 3, characterized in that, after the optical fiber is threaded in the step (4), the residual alcohol in the glass tube needs to be cleaned before tapering. 6 . A high-power laser beam combiner according to claim 3 , characterized in that, in the step (4), after the optical fiber bundle penetrates into the glass tube, the optical fiber bundle is fine-tuned through a microscope. 7. A high-power laser beam combiner according to claim 3, characterized in that, in the step (5), the length of the taper of the input fiber in the experiment is set to 13 mm, and the taper ratio is 1.3. 8. A high-power laser beam combiner according to claim 3, characterized in that the cutting angle of the fiber bundle in the step (6) is controlled within 0.5 degrees. 9 . A high-power laser beam combiner according to claim 3 , characterized in that, in the step (6), the outer side of the quartz glass tube is heated by a three-electrode ring fire method. 10. A kind of high-power laser beam combiner according to claim 1, is characterized in that, described sensing module is based on ARM and FPGA module and carries out multiple monitoring.