Special-shaped flat-topped light spot output power beam combiner and preparation method thereof

Abstract

The invention provides a special-shaped flat-topped light spot output power beam combiner and a preparation method thereof.The special-shaped flat-topped light spot output power beam combiner comprises a combined optical fiber bundle, a transition optical fiber and a special-fiber-core-shaped optical fiber, and after fused biconical taper is conducted on the combined optical fiber bundle, the combined optical fiber bundle is cut off from the taper waist to form a first taper area; the first taper area is connected with the input end of the transition optical fiber in a staggered fusion welding mode, the input end of the optical fiber in the special fiber core shape is subjected to fused biconical taper to form a second taper area, and the second taper area is directly connected with the output end of the transition optical fiber in a fusion welding mode. The shape of an output light spot is determined by the fiber core shape of the optical fiber with the special fiber core shape, and flat-topped light energy distribution is generated. The combined configuration of the combined optical fiber bundle, the transition optical fiber and the optical fiber with the special fiber core shape can excite more high-order modes so as to improve the uniformity of output light spots. The beam combiner does not need a special optical element for beam homogenization and shaping, so that the complexity of the system is reduced, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber laser synthesis, and in particular to a special-shaped flat-top spot output power combiner and a preparation method thereof. Background Art

[0002] Limited by factors such as thermal damage, nonlinear effects, pump brightness and mode instability, the increase in the output power of a single fiber laser has encountered a bottleneck, and fiber laser synthesis technology can well solve this problem. The fiber power combiner can combine the power of multiple medium-power fiber lasers to obtain higher-power fiber laser output, and is one of the core components for achieving high-power fiber laser output.

[0003] Moreover, in some applications where lasers are the core components, such as laser cutting, drilling, annealing, semiconductor manufacturing, laser medical surgery, laser nuclear fusion, etc., standard Gaussian beams may have uneven light intensity distribution in some applications, affecting the accuracy of laser applications and system performance. Most existing beam homogenization and shaping technologies are achieved through complex lens optical systems, which have high costs and complex system structures.

[0004] Fiber laser synthesis technology based on fiber power combiner can realize all-fiber high-power laser output, and the transmission characteristics of optical fiber can be used to convert laser beams into other uniformly distributed light field outputs. Compared with the beam shaping method of traditional spatial structure, the use of optical fiber for beam shaping has the advantages of simple and compact structure, high reliability, low cost, good stability, etc. Therefore, it is necessary to propose a special shape flat-top spot output power combiner. Summary of the invention

[0005] The purpose of the present invention is to provide a special-shaped flat-top spot output power combiner and a preparation method thereof, which can achieve high-power laser output through a simple optical fiber structure while maintaining the uniformity and specific shape of the light spot. Through special optical fiber fusion technology and core shape design, the uniformity of the light beam and the flexibility of application are improved.

[0006] According to one object of the present invention, the present invention provides a special-shaped flat-top spot output power combiner, comprising a combined fiber bundle, a transition fiber and a special core shape fiber, the combined fiber bundle is melt-tapered and then cut from the waist to form a first cone region, the first cone region is connected to the input end of the transition fiber by offset fusion splicing, the input end of the special core shape fiber is melt-tapered to form a second cone region, the second cone region is directly fusion spliced ​​to the output end of the transition fiber.

[0007] Furthermore, the combined optical fiber bundle includes a glass tube and no less than three input optical fibers 7, and the input optical fibers 7 are uniformly stripped of coating layers and closely arranged in the glass tube.

[0008] Furthermore, the input optical fibers 7 are closely arranged in a circumferential form inside the glass tube.

[0009] Furthermore, the core diameter of the transition optical fiber is larger than the core bundle diameter of the first cone region.

[0010] Furthermore, when the transition optical fiber is fused with the first cone region, the core is offset in the radial direction, and the offset distance is less than or equal to the radius difference between the core of the transition optical fiber and the core of the first cone region.

[0011] Furthermore, the core diameter of the second tapered region is close to the core diameter of the transition optical fiber, and the core of the second tapered region completely covers the core of the transition optical fiber.

[0012] Furthermore, the combined optical fiber bundle is melt-tapered, and the taper ratio is 0.4-0.6.

[0013] Furthermore, the length of the first cone region is 5 mm-15 mm.

[0014] Furthermore, the length of the second tapered region is 5 mm-15 mm.

[0015] According to another object of the present invention, the present invention provides a method for preparing the above-mentioned special-shaped flat-top spot output power combiner, comprising the following steps:

[0016] S1, stripping a certain length of the coating layer of the input optical fiber and arranging them closely in a low-refractive-index glass tube, performing melt taper drawing to form an optical fiber bundle, and cutting the optical fiber bundle at the taper waist to obtain a first taper region;

[0017] S2, the input end of the transition optical fiber is staggered with the first cone region for a certain distance for fusion splicing;

[0018] S3, by tapering the input end of the special core shape optical fiber to form a second cone region, the second cone region is directly fused and connected to the output end of the transition optical fiber to achieve mode field matching between the transition optical fiber and the output optical fiber; the output light spot shape is the same as the core shape of the special shape core optical fiber, and the laser energy distribution is a flat-top distribution.

[0019] The core shape of the special core shape optical fiber of the technical solution of the present invention determines the shape of the output light spot and produces a flat-top light energy distribution. The combined configuration of the combined fiber bundle, transition fiber and special core shape optical fiber can excite more high-order modes to improve the uniformity of the output light spot. The beam combiner does not require special optical elements for beam homogenization and shaping, thereby reducing the complexity of the system and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of the structure of an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the arrangement of the combined optical fiber bundle according to an embodiment of the present invention;

[0023] Figure 3 It is a structural diagram of the combined optical fiber bundle and the first cone region according to an embodiment of the present invention;

[0024] Figure 4 It is a schematic structural diagram of the staggered fusion of the first cone region and the transition optical fiber according to an embodiment of the present invention;

[0025] Figure 5 It is a schematic structural diagram of an optical fiber with a special core shape and a second cone region according to an embodiment of the present invention;

[0026] Figure 6 It is a cross-sectional view of an optical fiber with a special core shape according to an embodiment of the present invention.

[0027] In the figure: 1. Combined fiber bundle; 2. Transition fiber; 3. Fiber with special core shape; 4. First cone region; 5. Second cone region; 6. Glass tube; 7. Input fiber; 8. Coating layer; 9. Core; 10. Cladding. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0030] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Example 1

[0032] like Figure 1-Figure 6 As shown,

[0033] A special-shaped flat-top spot output power combiner comprises a combined fiber bundle 1, a transition fiber 2 and a special core-shaped fiber 3. The combined fiber bundle 1 is cut from the waist of the cone after being melt-tapered to form a first cone region 4. The first cone region 4 is connected to the input end of the transition fiber 2 by staggered fusion splicing. The input end of the special core-shaped fiber 3 is melt-tapered to form a second cone region 5, which is directly fusion-spliced ​​to the output end of the transition fiber 2.

[0034] like Figure 2 As shown, the combined optical fiber bundle 1 includes a glass tube 6 and N (N≥3) identical input optical fibers 7. In this embodiment, the input optical fibers 7 include N (N≥3) input optical fibers. The N input optical fibers 7 are stripped of a certain length of coating and their end faces are cut flat, and then closely arranged in a circular form in the glass tube 6 to form the combined optical fiber bundle 1.

[0035] like Figure 3As shown, the combined optical fiber bundle 1 composed of the glass tube 6 and N input optical fibers 7 is melt-tapered with a taper ratio of 0.4-0.6, and then the combined optical fiber bundle 1 is cut from the waist to form a first taper region 4. The length of the first taper region 4 is 5mm-15mm. At this time, the closely arranged N input optical fibers 7 are equivalent to the core of the first taper region 4, and the glass tube 6 is equivalent to the cladding of the first taper region 4.

[0036] like Figure 4 As shown, a certain length of coating 8 is stripped off the input end and the output end of the transition optical fiber 2 and cut flat, the core diameter of the transition optical fiber 2 should be larger than the diameter of the optical fiber bundle in the first cone region 4, and the input end of the transition optical fiber 2 is staggered and fused with the first cone region 4. When the transition optical fiber 2 and the first cone region 4 are staggered and fused, the radial offset distance of the core is less than or equal to the radius difference between the transition optical fiber 2 and the first cone region 4, thereby exciting more modes and obtaining higher uniformity.

[0037] like Figure 5 and Figure 6 As shown, the special core shape optical fiber 3 includes a core 9 and a cladding 10, and the core 9 is coated inside the cladding 10. The input end of the special core shape optical fiber 3 is melt-stripped to remove a certain length of the coating layer 8 and cut flat, and then melt-drawn to form a second cone area 5. The length of the second cone area 5 is 5mm-15mm, and the core diameter of the second cone area 5 is close to the core diameter of the transition optical fiber 2. The core of the special core shape optical fiber 3 completely covers the core of the transition optical fiber, and the core of the second cone area 5 should completely cover the core of the transition optical fiber 2, and the output end of the transition optical fiber 2 is fused with the second cone area 5.

[0038] By fusion tapering the special core shape optical fiber 3 and then splicing it to the transition optical fiber 2, the light beam can be transmitted in an optical fiber with a larger core diameter, and a better mode matching effect can be achieved during splicing. According to the normalized frequency formula of the optical fiber: It can be seen that the larger the core of the optical fiber, the more modes are allowed to exist in the optical fiber. The number of modes that can exist can be expressed as The excitation of more modes will also improve the uniformity of the beam and achieve a flat-top spot output.

[0039] Example 2

[0040] The structure of this embodiment is basically the same as that of embodiment 1. In this embodiment, seven identical multimode optical fibers are used as input optical fibers 7, with a size of 200 / 220 μm, that is, a core diameter of 200 μm, a cladding diameter of 220 μm, an optical fiber numerical aperture of 0.22, a taper ratio of the first cone region 4 of 0.5, a size of the transition optical fiber 2 of 400 / 440 μm, an optical fiber numerical aperture of 0.22, an offset distance of the staggered fusion of the first cone region 4 and the transition optical fiber 2 of 35 μm, and a More modes are excited through offset fusion. The special core shape optical fiber 3 uses a square core optical fiber with a core diameter of 800×800μm and a cladding diameter of 1400μm. The taper ratio is 0.5 to form a second cone region 5. The transition optical fiber 2 is fused with the second cone region 5. The light beam can propagate in an optical fiber with a larger core diameter, which can excite more modes and shape the light beam into the shape of the optical fiber core, thereby realizing a special shape flat-top spot output. The result achieved in this embodiment is a square flat-top spot output.

[0041] The special-shaped flat-top spot output power combiner of the present invention comprises the following steps:

[0042] After a certain length of coating layer 8 is stripped off the input optical fiber 7, it is closely arranged in a low-refractive index glass tube 6, and melt-tapered to form an optical fiber bundle, and the optical fiber bundle is cut at the waist of the cone to obtain a first cone area 4; the input end of the transition optical fiber 2 is offset from the first cone area 4 for a distance and fused, and the second cone area 5 is formed by tapering the input end of the special core shape optical fiber 3, and the second cone area is fused with the output end of the transition optical fiber 2, which can achieve mode field matching between the transition optical fiber and the output optical fiber; the output light spot shape is the same as the core shape of the special shape core optical fiber, and the laser energy distribution is a flat-top distribution, which solves the problem of unstable effect and small application range of traditional laser homogenization methods.

[0043] The present invention does not require special optical elements to homogenize and shape the light beam, thus avoiding a complex optical system structure and realizing the homogenization and shaping of the light beam, and has the advantages of simple structure, good compactness and strong stability.

[0044] The special-shaped flat-top spot output power combiner of the present invention adopts an N×1 fiber beam combining structure to achieve high-power laser output, and the first cone region is staggered and fused with the transition fiber to disrupt the original transmission mode of the light beam, stimulate more high-order modes, and obtain a light beam with higher uniformity without excessive loss. In addition, by fusing a special core-shaped optical fiber with a larger core diameter as the output optical fiber, more transmission modes can be stimulated, thereby generating homogenized light spots of different shapes. This case does not require special optical elements to homogenize and shape the light beam, avoiding a complex optical system structure, and has the advantages of simple structure, good compactness, and strong stability.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A special-shaped flat-top spot output power combiner, characterized in that: The invention comprises a combined optical fiber bundle, a transition optical fiber and an optical fiber with a special core shape. The combined optical fiber bundle is cut from the cone waist after being melt-tapered to form a first cone region, the first cone region is connected to the input end of the transition optical fiber by staggered fusion splicing, the input end of the optical fiber with a special core shape is melt-tapered to form a second cone region, the second cone region is directly fusion spliced ​​to the output end of the transition optical fiber.

2. The special-shaped flat-top spot output power combiner according to claim 1, characterized in that: The combined optical fiber bundle includes a glass tube and no less than three input optical fibers 7. The coating layers of the input optical fibers 7 are uniformly stripped and closely arranged in the glass tube.

3. The special-shaped flat-top spot output power combiner according to claim 2, characterized in that: The input optical fibers 7 are closely arranged in a circumferential form inside the glass tube.

4. The special-shaped flat-top spot output power combiner according to claim 1, characterized in that: The core diameter of the transition optical fiber is larger than the core bundle diameter of the first cone region.

5. The special-shaped flat-top spot output power combiner according to claim 1, characterized in that: When the transition optical fiber is fused with the first cone region, the core is offset in the radial direction, and the offset distance is less than or equal to the radius difference between the core of the transition optical fiber and the core of the first cone region.

6. The special-shaped flat-top spot output power combiner according to claim 1, characterized in that: The core diameter of the second tapered region is close to the core diameter of the transition optical fiber, and the fiber core of the second tapered region completely covers the fiber core of the transition optical fiber.

7. The special-shaped flat-top spot output power combiner according to claim 1, characterized in that: The combined optical fiber bundle is melt-tapered, and the taper ratio is 0.4-0.

6.

8. The special-shaped flat-top spot output power combiner according to claim 1, characterized in that: The length of the first tapered region is 5 mm-15 mm.

9. The special-shaped flat-top spot output power combiner according to claim 1, characterized in that: The length of the second tapered area is 5 mm-15 mm.

10. The method for preparing a special-shaped flat-top spot output power combiner according to any one of claims 1 to 9, characterized in that: The steps include: S1, stripping a certain length of the coating layer of the input optical fiber and arranging them closely in a low-refractive-index glass tube, performing melt taper drawing to form an optical fiber bundle, and cutting the optical fiber bundle at the taper waist to obtain a first taper region; S2, the input end of the transition optical fiber is staggered with the first cone region for a certain distance for fusion splicing; S3, by tapering the input end of the special core shape optical fiber to form a second cone region, the second cone region is directly fused and connected to the output end of the transition optical fiber to achieve mode field matching between the transition optical fiber and the output optical fiber; the output light spot shape is the same as the core shape of the special shape core optical fiber, and the laser energy distribution is a flat-top distribution.

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