A fiber laser and laser processing equipment

Abstract

This invention discloses a fiber laser and laser processing equipment. The fiber laser includes a pump source, an active optical fiber, and high-reflection gratings and low-reflection gratings disposed on the active optical fiber. The pump source includes at least one light source and a lens, wherein the pump source is used to emit pump light; the lens is located in the optical path between the light source and a first end of the active optical fiber, coupling the pump light into the active optical fiber; the active optical fiber is used to convert at least a portion of the pump light into signal laser. This invention, by using an active optical fiber and high- and low-reflection gratings etched on the active optical fiber, can convert at least a portion of the pump light output from the pump source into signal laser output. This eliminates the need for a passive optical fiber with etched fiber gratings in the fiber laser, thus preventing the introduction of fusion splices when connecting the passive and active optical fibers, thereby solving the problems of poor reliability and low output beam brightness in existing fiber lasers.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, and in particular to a fiber laser and laser processing equipment. Background Technology

[0002] Currently, fiber lasers, with their high electro-optical efficiency and high brightness, have shown great advantages in the industrial processing sector and have been rapidly developed as a powerful processing tool.

[0003] However, in existing fiber lasers, the gain material used in the resonant cavity is active fiber, while the fiber grating, which serves as the resonant cavity mirror, is inscribed on passive fiber. This structure has significant drawbacks.

[0004] On the one hand, it is difficult to achieve a perfect percentage match between passive and active optical fibers. Connecting passive and active fibers requires introducing a fusion splice. Mismatches between the splice and the fiber can lead to optical loss, resulting in low laser power, internal light leakage, high temperature, and decreased long-term reliability of the laser. On the other hand, it can also degrade beam quality, reducing the output brightness of the fiber laser. Utility Model Content

[0005] This invention provides a fiber laser and laser processing equipment to solve the problem that existing fiber lasers require passive optical fibers with inscribed fiber gratings, which introduce fusion splices when connecting passive and active optical fibers, resulting in poor reliability and low output beam brightness in the fiber laser.

[0006] In a first aspect, this utility model provides a fiber laser, including a pump source, an active optical fiber, and a high-reflectivity grating and a low-reflectivity grating disposed on the active optical fiber.

[0007] The pump source includes at least one light source and a lens, and the pump source is used to emit pump light;

[0008] The lens is located in the optical path between the light source and the first end of the active optical fiber, and couples the pump light into the active optical fiber;

[0009] The active optical fiber is used to convert at least a portion of the pump light into signal laser light.

[0010] Optionally, an end cap is also included, wherein the second end of the active optical fiber is directly connected to the end cap to form a laser output head.

[0011] Optionally, the reflectivity of the high-reflectivity grating is greater than that of the low-reflectivity grating;

[0012] The high-reflectivity grating is disposed at the first end of the active optical fiber, and the low-reflectivity grating is located on the side of the high-reflectivity grating away from the pump source.

[0013] Optionally, the low-reflection grating is disposed between the first end and the second end of the active optical fiber, or the low-reflection grating is disposed at the second end of the active optical fiber.

[0014] Optionally, the active optical fiber includes a fiber core and an optical fiber cladding, wherein the optical fiber cladding wraps around the fiber core;

[0015] The diameter of the fiber core gradually increases from the first end to the second end of the active optical fiber.

[0016] Optionally, the diameter of the fiber core increases linearly or non-linearly from the first end to the second end of the active optical fiber.

[0017] Optionally, the outer diameter of the fiber cladding at the first end of the active optical fiber is equal to the outer diameter at the second end of the active optical fiber.

[0018] Optionally, it also includes a tilted grating, which is inscribed on the active optical fiber and is located on the side of the low-reflection grating away from the high-reflection grating.

[0019] Optionally, it also includes a long-period grating, which is inscribed on the active optical fiber and is located on the side of the low-reflection grating away from the high-reflection grating.

[0020] Secondly, this utility model provides a laser processing device, including the fiber laser described in the first aspect.

[0021] The technical solution of this utility model embodiment, by setting an active optical fiber directly connected to the pump source, converts at least a portion of the pump light output from the pump source into signal laser output. This eliminates the need for a passive optical fiber with a fiber grating to be inscribed in the fiber laser of this utility model. As a result, no fusion splices are introduced when the passive optical fiber is connected to the active optical fiber. There are no dissimilar optical fibers, and the transmission waveguides are perfectly matched. This solves the problems of poor reliability and low output beam brightness in existing fiber lasers, resulting in a high-brightness laser.

[0022] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of the structure of a fiber laser provided in an embodiment of this utility model;

[0025] Figure 2 A schematic diagram of another fiber laser provided in this embodiment of the present invention;

[0026] Figure 3 A schematic diagram of another fiber laser provided in this embodiment of the present invention;

[0027] Figure 4 A schematic diagram of another fiber laser provided in this embodiment of the present invention;

[0028] Figure 5 A schematic diagram of another fiber laser provided in this embodiment of the present invention;

[0029] Figure 6 This is a schematic diagram of the structure of a laser processing device provided in an embodiment of the present utility model. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] Figure 1 This is a schematic diagram of the structure of a fiber laser provided in an embodiment of the present invention, with reference to... Figure 1 The fiber laser in this embodiment includes a pump source 10, an active optical fiber 20, and a high-reflection grating 30 and a low-reflection grating 40 disposed on the active optical fiber 20. The pump source 10 includes at least one light source 11 and a lens 12, and is used to emit pump light. The lens 12 is located in the optical path between the light source 11 and the first end of the active optical fiber 20, coupling the pump light into the active optical fiber 20. The active optical fiber 20 is used to convert at least a portion of the pump light into a signal laser, wherein the pump light and the signal laser have different wavelengths.

[0033] For example, the light source 11 in this embodiment of the present invention can be a laser chip. Multiple light sources 11 can form a laser chip array. The beams emitted by these laser chip arrays are collimated and bundled to form pump light. One or more pump lights are converged by lens 12 and incident on the first end of the active optical fiber 20. Through the lens 12, the pump light output from the pump source 10 and the active fiber 20 are coupled spatially. Only the head of the active fiber 20 needs to be installed in the appropriate position, replacing the need for a combiner that would otherwise be fused to the light source 11 and the active fiber separately. Thus, there are no fusion points between the pump source 10 and the active fiber 20, reducing pump light leakage and improving pump light quality. Since no combiner is needed, the pump light directly from the pump source has a smaller divergence angle (NA) and higher absorption rate. Furthermore, the active fiber 20 runs through the entire optical path of the fiber laser, resulting in more complete pump light absorption and less residual pump light. Therefore, the cladding mode stripper can be eliminated, further reducing fusion points and lowering device costs. Moreover, when the active fiber 20 needs maintenance, it can be quickly disassembled and repaired separately, making maintenance convenient and cost-effective.

[0034] Figure 1The key structure of the pump source 10 is only briefly shown in the figure. The actual pump source 10 also includes components such as a fast-axis collimator (FAC), a slow-axis collimator (SAC), a polarization combiner, and a filter.

[0035] The pump light emitted from pump source 10 is absorbed by active fiber 20, causing electrons within the active fiber 20 to transition to higher energy levels. These higher energy levels then emit stimulated emission, emitting a signal laser with a wavelength selected by a fiber grating, thus converting the pump light into a signal laser with a different wavelength. Specifically, the active fiber 20 between the high-reflection grating 30 and the low-reflection grating 40, together with the high-reflection grating 30 and the low-reflection grating 40, forms a resonant cavity, generating a low-power, high-beam-quality seed laser (signal seed source). The active fiber 20 between the low-reflection grating 40 and the second end of the active fiber 20 acts as an amplification stage, amplifying the seed laser to form a high-power signal laser.

[0036] In this embodiment of the invention, the active optical fiber 20 can be ytterbium-doped fiber, which is a fiber based on ytterbium ions (Yb). 3+ The active optical fiber serves as the gain medium. It is understood that existing active optical fibers have limited lengths; to absorb pump light over short distances, highly doped active optical fibers are required. However, the active optical fiber 20 in this embodiment replaces the original passive optical fiber, thus its length is longer. Using low-doped ytterbium-doped fiber can effectively absorb pump light and reduce photon darkening. Highly doped ytterbium-doped fiber is relatively expensive; this application uses low-doped ytterbium-doped fiber, resulting in a lower overall cost.

[0037] This embodiment of the invention, by setting an active optical fiber 20 and a high-reflection fiber grating 30 and a low-reflection fiber grating 40 on the active optical fiber 20, can convert at least a portion of the pump light output from the pump source 10 into signal laser output. This eliminates the need for a passive optical fiber with inscribed fiber gratings in the fiber laser of this invention, thus preventing the introduction of fusion splices when the passive optical fiber is connected to the active optical fiber 20. This solves the problems of poor reliability and low output beam brightness in existing fiber lasers.

[0038] Figure 2 This is a schematic diagram of another fiber laser provided in an embodiment of the present invention, with reference to... Figure 2 The fiber laser in this embodiment of the present invention also includes an end cap 50, and the second end of the active optical fiber 20 is directly connected to the end cap 50 to form a laser output head.

[0039] Existing laser output heads (QBHs) typically consist of an end cap fused to a passive optical fiber, which is then fused with an active optical fiber to form a fiber-to-fiber fusion splice. In this embodiment, the end cap 50 can be made of quartz. The end cap 50 protects the second end face of the active optical fiber 20 and enhances its ability to carry high-power laser signals. A laser output head capable of outputting high-power laser signals can be formed by directly connecting the end cap 50 to the second end of the active optical fiber 20.

[0040] Compared to existing laser output heads, the active optical fiber 20 and end cap 50 in this invention can be directly fused together, without any fiber-to-fiber fusion splices, which facilitates the integration of the laser optical path. It should be noted that the integration of the entire laser optical path means that from the front-end pump source 10 of the laser optical path to the active optical fiber 20, and to the end laser output head, the entire structure forms a single, integrated structure without any fiber-to-fiber fusion splices in between.

[0041] Continue to refer to Figure 1 and Figure 2 The reflectivity of the high-reflectivity grating 30 is greater than that of the low-reflectivity grating 40. The high-reflectivity grating 30 is located at the first end of the active optical fiber 20, and the low-reflectivity grating 40 is located on the side of the high-reflectivity grating 30 away from the pump source 10.

[0042] It should be noted that the length of the resonant cavity is determined by the length of the active optical fiber 20 between the high-reflection grating 30 and the low-reflection grating 40. Different resonant cavity lengths result in different signal seed source power. The power of the signal seed source can be flexibly designed by setting the positions of the high-reflection grating 30 and the low-reflection grating 40.

[0043] Existing fiber lasers use passive optical fibers to inscribe fiber gratings, inevitably introducing fusion splices between the high-reflection gratings and low-reflection gratings and the active optical fiber. These splices easily lead to optical energy loss, mode field degradation, heat generation, and decreased beam quality. Furthermore, since passive and active optical fibers are dissimilar, achieving perfect matching is difficult and also results in energy degradation. In this embodiment, both the high-reflection grating 30 and the low-reflection grating 40 can be inscribed entirely on the active optical fiber 20. The high-reflection grating 30, the low-reflection grating 40, and the active optical fiber 20 located between them have no fusion splices, eliminating dissimilar fiber types and ensuring perfect waveguide matching. Theoretically, this allows for zero energy attenuation, no mode field degradation, and high laser brightness.

[0044] Based on the above embodiments, Figure 3 A schematic diagram of another fiber laser provided in this embodiment of the present invention is shown below. Figure 3 The low-reflection grating 40 is inscribed between the first end and the second end of the active optical fiber 20, or, refer to Figure 1 and Figure 2 The low-reflectivity grating 40 is disposed at the second end of the active optical fiber 20.

[0045] refer to Figure 1 , Figure 2 and Figure 3 It should be noted that the low-reflection grating 40 in this embodiment can be set at any position of the active optical fiber 20. Those skilled in the art can set it according to the requirements of resonant cavity type, pumping method and thermal management, etc. This embodiment does not limit it in this respect. Figure 1 , Figure 2 and Figure 3 The embodiment shown is illustrated using unidirectional pumping (forward pumping) as an example. Compared to the low-reflection grating 40, the high-reflection grating 30 is closer to the pump source, which is beneficial to improving the efficiency of signal seed source generation.

[0046] It should be noted that existing fiber laser resonator pumping schemes mainly use three pumping methods: forward pumping (pump light and signal laser propagation directions are the same), backward pumping (pump light and signal laser propagation directions are opposite), and bidirectional pumping (combining forward and backward pumping). Considering that the end face of ordinary active fiber 20 cannot simultaneously achieve efficient signal laser output and pump light input, direct coupling will lead to pump light leakage or signal laser reflection loss. Backward pumping and bidirectional pumping use a reverse beam combiner, but the reverse beam combiner has the problems of high manufacturing difficulty and cost, and is prone to introducing loss. At the same time, it is difficult to make the fibers at both ends have the same core diameter. Forward pumping is prone to serious problems such as stimulated Raman scattering and TMI (transverse mode instability) due to the mismatch in intensity distribution of pump light and signal laser along the fiber axis, which greatly restricts the power and laser brightness of fiber lasers. To solve the problems of stimulated Raman scattering and TMI, this utility model embodiment improves the fiber core of active fiber 20, as detailed in the following embodiment.

[0047] Figure 4 A schematic diagram of another fiber laser provided in this embodiment of the present invention is shown below. Figure 4 The active optical fiber 20 in this embodiment of the present invention includes a fiber core 21 and an optical fiber cladding 22, with the optical fiber cladding 22 wrapping around the fiber core 21. The direction from the first end of the active optical fiber 20 to the second end of the active optical fiber 20 ( Figure 5 As shown in the direction X), the diameter of the fiber core 21 gradually increases.

[0048] For example, the core 21 of the active optical fiber 20 is mainly used for signal transmission and amplification, while the cladding 22 of the active optical fiber 20 is mainly used for pump light transmission, heat dissipation and protection.

[0049] In this embodiment of the invention, the core 21 of the active optical fiber 20 is gradually increased in diameter, extending from the first end to the second end of the active optical fiber 20. When the active optical fiber 20 is used in a resonant cavity, the pump light at the first end of the active optical fiber 20 is large, but the core 21 is small, resulting in minimal absorption of the pump light by the core 21. Along the axial direction of the active optical fiber 20, the pump light gradually weakens, and the core 21 gradually increases in size, again resulting in minimal absorption of the pump light by the core 21. Throughout the process, the absorption of the pump light by the core 21 remains essentially constant. Thus, the pump light can be applied along the length of the active optical fiber 20 (…). Figure 5 The absorption is uniform in the direction X shown, and the amplification of the signal laser is also relatively uniform. Thus, the heating of each segment of the active fiber in the entire laser is relatively uniform, reducing thermal distortion, decreasing stimulated Raman scattering and TMI, and resulting in good beam quality.

[0050] Based on the above embodiments, continue to refer to Figure 4 The diameter of the fiber core 21 increases linearly or nonlinearly from the first end of the active optical fiber 20 to the second end of the active optical fiber 20.

[0051] It should be noted that this embodiment of the invention does not limit whether the diameter of the fiber core 21 increases linearly or nonlinearly. Those skilled in the art can set it according to the laser power requirements and manufacturing costs.

[0052] Based on the above embodiments, continue to refer to Figure 4 In this embodiment of the present invention, the outer diameter of the optical fiber cladding 22 at the first end of the active optical fiber 20 is equal to the outer diameter at the second end of the active optical fiber 20.

[0053] For example, in this embodiment of the present invention, the outer diameter of the fiber cladding 22 remains constant along the direction from the first end to the second end of the active fiber 20, to ensure that when the pump light at the first end of the active fiber 20 is large, the cross-sectional area of ​​the fiber cladding 22 is large, which will not affect the high transmission efficiency. In this embodiment of the present invention, the active fiber 20 can be achieved by a fiber preform profile drawing method.

[0054] Figure 5 A schematic diagram of another fiber laser provided in this embodiment of the present invention is shown below. Figure 5 The fiber laser in this embodiment of the present invention also includes a tilted grating 60, which is inscribed on the active optical fiber 20 and is located on the side of the low-reflection grating 40 away from the high-reflection grating 30.

[0055] exist Figure 5In the illustrated embodiment, the fiber laser includes three tilt gratings 60, preferably chirped tilted Bragg fiber gratings, which can suppress stimulated Raman scattering (SRS) caused by nonlinear effects and avoid problems such as unstable optical power, deteriorated beam quality, or even optical path burnout caused by SRS. Those skilled in the art can set the number of tilt gratings 60 as they see fit, and this embodiment of the present invention does not limit this.

[0056] Based on the above embodiments, continue to refer to Figure 5 The fiber laser in this embodiment of the present invention also includes a long-period grating 70, which is inscribed on the active optical fiber 20 and is located on the side of the low-reflection grating 40 away from the high-reflection grating 30.

[0057] The long-period grating 70 can suppress high-order modes by coupling them to the fiber cladding 22 and then losing them, which is beneficial to improving the beam quality of the laser. It can also couple low-order LP01 modes to low-order modes such as LP11, and adapt to different processing scenarios of the laser by changing the distribution of the optical field energy. In broadband fiber lasers (such as erbium-doped fiber lasers), the long-period grating 70 can compensate for the non-uniform spectral response of the gain medium. By stretching, heating or applying stress to change the period of the long-period grating 70, the position of the loss peak can be dynamically adjusted, and wavelength switching can be achieved in multi-wavelength lasers. In high peak power lasers, the long-period grating 70 can selectively lose Stokes light and delay the stimulated Raman scattering threshold. The long-period grating 70 is sensitive to external temperature / strain, and can monitor the laser status in real time and adjust the pump power accordingly.

[0058] Based on the same concept, this utility model embodiment also provides a laser processing device. Figure 6 This is a schematic diagram of the structure of a laser processing device provided in an embodiment of the present invention, with reference to... Figure 6 The laser processing equipment 200 in this embodiment includes the fiber laser 100 provided in any of the above embodiments of this utility model. Therefore, the laser processing equipment 200 includes the technical features of the fiber laser 100 and possesses the beneficial effects of the fiber laser 100. The similarities can be referred to the description above.

[0059] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fiber laser, characterized by, It includes a pump source, an active optical fiber, and a high-reflectivity grating and a low-reflectivity grating disposed on the active optical fiber; The pump source includes at least one light source and a lens, and the pump source is used to emit pump light; The lens is located in the optical path between the light source and the first end of the active optical fiber, and couples the pump light into the active optical fiber; The active optical fiber is used to convert at least a portion of the pump light into signal laser light.

2. The fiber laser of claim 1, wherein, It also includes an end cap, to which the second end of the active optical fiber is directly connected to form a laser output head.

3. The fiber laser of claim 1, wherein, The reflectivity of the high-reflectivity grating is greater than that of the low-reflectivity grating; The high-reflectivity grating is disposed at the first end of the active optical fiber, and the low-reflectivity grating is located on the side of the high-reflectivity grating away from the pump source.

4. The fiber laser of claim 3, wherein, The low-reflection grating is disposed between the first end and the second end of the active optical fiber, or the low-reflection grating is disposed at the second end of the active optical fiber.

5. The fiber laser of claim 1, wherein, The active optical fiber includes a fiber core and an optical fiber cladding, wherein the optical fiber cladding wraps around the fiber core; The diameter of the fiber core gradually increases from the first end to the second end of the active optical fiber.

6. The fiber laser of claim 5, wherein, The diameter of the fiber core increases linearly or non-linearly from the first end to the second end of the active optical fiber.

7. The fiber laser of claim 5, wherein, The outer diameter of the optical fiber cladding at the first end of the active optical fiber is equal to the outer diameter at the second end of the active optical fiber.

8. The fiber laser of claim 4, wherein, It also includes a tilted grating, which is inscribed on the active optical fiber and is located on the side of the low-reflection grating away from the high-reflection grating.

9. The fiber laser of claim 4, wherein, It also includes a long-period grating, which is inscribed on the active optical fiber and is located on the side of the low-reflection grating away from the high-reflection grating.

10. A laser processing apparatus characterized by comprising: Includes the fiber laser according to any one of claims 1-9.

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