Variable light spot fiber laser with single-cavity all-fiber structure

Abstract

The single-cavity all-fiber structure variable light spot fiber laser comprises a fiber laser light source, a transition fiber, a multi-cladding fiber and an output optical cable, the output optical fiber of the fiber laser light source is connected with the transition fiber, the transition fiber is connected with the multi-cladding fiber, and the multi-cladding fiber is connected with the output optical cable. The transition optical fiber and the multi-cladding optical fiber have the same outer cladding diameter, the multi-cladding optical fiber penetrates through the hollow telescopic pipe, the two ends of the multi-cladding optical fiber are exposed out of the hollow telescopic pipe, the hollow telescopic pipe surrounds the hollow telescopic pipe by a plurality of circles and extends in a spiral shape, and the multi-cladding optical fiber and the hollow telescopic pipe are connected with each other under the condition that the length of the multi-cladding optical fiber and the length of the hollow telescopic pipe are kept unchanged. The larger the stretching degree of the hollow telescopic pipe is, the larger the bending radius of the multi-cladding optical fiber is, and the smaller the stretching degree of the hollow telescopic pipe is, the smaller the bending radius of the multi-cladding optical fiber is. The device is easy and convenient to assemble, small in size and capable of achieving continuous modulation of a laser output mode.

Description

Technical Field

[0001] The invention relates to a laser, in particular to a single-cavity all-fiber structure variable spot optical fiber laser. Background Art

[0002] In modern laser processing applications, a single spot mode is difficult to cope with changing processing conditions and has obvious limitations. Lasers that achieve variable spots based on spatial optical systems have high material costs, and debugging is difficult and time-consuming, resulting in high manufacturing costs. In addition, they are unstable and have poor vibration resistance.

[0003] The patent with publication number CN 111736355A discloses an optical system based on microlens group with adjustable energy distribution, including a first positive focus lens, a first negative focus lens, a second positive focus lens, a plano-concave microlens, a plano-convex microlens, a third positive focus lens, a second negative focus lens and a fourth positive focus lens. The present invention has a novel structural design, realizes the characteristics of point light spot and point-ring combination light spot based on the cooperation of microlens and focusing mirror, realizes the characteristics of collimated light spot size, focused light spot size and beam divergence angle and focus position compensation adjustment based on ZOOM optical system, and realizes the continuously adjustable focusing beam divergence angle, point light spot to point-ring combination light spot, point light spot size, ring light spot middle diameter and thickness, and point-ring light spot energy ratio by rotating one of the microlenses at a small angle along the beam transmission axis in combination with the adjustment of the double ZOOM optical system.

[0004] The variable spot laser based on the current all-fiber beam combining optical system essentially achieves spot modulation by adjusting the output ratio of each part of the pump module; this will definitely increase the manufacturing cost and make the product expensive. The patent application with publication number CN117154514A discloses a small core diameter dual-beam fiber laser, including a beam combining module and at least one optical path mother module, the optical path mother module includes a first optical resonant cavity and a second optical resonant cavity, the first optical resonant cavity and the second optical resonant cavity are partially overlapped and at least one section of shared gain fiber is provided at the overlap, the output ends of the first optical resonant cavity and the second optical resonant cavity are both connected to the beam combining module, the other end of the beam combining module is connected to a mode field converter, and the mode field converter is connected to an output end cap. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a single-cavity all-fiber structure variable spot fiber laser.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A single-cavity all-fiber structure variable spot fiber laser comprises a fiber laser light source, a transition fiber, a multi-clad fiber and an output optical cable. The output fiber of the fiber laser light source is connected to the transition fiber, the transition fiber is connected to the multi-clad fiber, the multi-clad fiber is connected to the output optical cable, the transition fiber and the multi-clad fiber have the same outer cladding diameter, the multi-clad fiber passes through a hollow telescopic tube, both ends of the multi-clad fiber are exposed outside the hollow telescopic tube, the hollow telescopic tube is spirally extended around several circles, and when the lengths of the multi-clad fiber and the hollow telescopic tube remain unchanged, the greater the stretching degree of the hollow telescopic tube, the greater the bending radius of the multi-clad fiber, and the smaller the stretching degree of the hollow telescopic tube, the smaller the bending radius of the multi-clad fiber.

[0008] As a further improvement, the interior of the hollow telescopic tube includes a Teflon sleeve tube, the multi-clad optical fiber passes through the sleeve tube, the hollow telescopic tube is made of plastic or metal material with low laser absorption rate, and a fixed structure is provided at the port of the multi-clad optical fiber and the hollow telescopic tube.

[0009] As a further improvement, CPS devices are respectively provided at the connection position between the output optical fiber of the fiber laser light source and the transition optical fiber, and at the connection position between the transition optical fiber and the output optical cable.

[0010] As a further improvement, the multi-clad optical fiber includes a core, a first cladding, a second cladding, a third cladding and a fluorine coating layer, the refractive index of the core is n41, the refractive index of the first cladding is n42, the refractive index of the second cladding is n43, the refractive index of the third cladding is n44, and the refractive index of the fluorine coating layer is n45, and the refractive indices satisfy the following relationship: n41>n42>n43>n44>n45.

[0011] As a further improvement, the core refractive index NA41 of the core, the core refractive index NA42 of the first cladding, the core refractive index NA43 of the second cladding, and the core refractive index NA44 of the third cladding are set, and the refractive index of each core layer satisfies the following relationship: NA41 <NA42<NA43<NA44。

[0012] As a further improvement, when the hollow telescopic tube is compressed to a minimum, the minimum bending radius of the hollow telescopic tube is greater than the macrobending critical radius of the third cladding.

[0013] As a further improvement, the hollow telescopic tube is wound around at least 5 times, and the minimum bending radius of each circle is greater than or equal to 30 mm.

[0014] As a further improvement, the hollow telescopic tube is stretched and assembled along an arc when stretched.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] No complicated optical lens group is required, only one laser cavity is needed, which is compact, lighter, low-cost, and has an optical fiber structure. No laser beam combiner is required, so the production difficulty is low and the reliability is better. A rainbow ring structure is formed by using a hollow telescopic tube that is wrapped around the ring. The bending radius of each layer of multi-clad optical fiber with different refractive indices is continuously modulated through the rainbow ring structure, thereby realizing continuous modulation of the laser output mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the present invention;

[0018] Figure 2 It is a schematic diagram of the structure formed by the hollow telescopic tube in the present invention;

[0019] Figure 3 It is a schematic diagram of the hollow telescopic tube of the present invention when it is compressed to the minimum state;

[0020] Figure 4 It is a schematic diagram of the hollow telescopic tube of the present invention in a state of a relatively small stretching degree;

[0021] Figure 5 This is a schematic diagram of the hollow telescopic tube of the present invention in a state of being stretched to a large extent;

[0022] Figure 6 is a schematic diagram of the cross-sectional structure of the multi-clad optical fiber of the present invention;

[0023] Figure 7 The figure is a schematic diagram of an installation structure of the hollow telescopic tube of the present invention.

[0024] Reference numerals: DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0026] In the description of the present invention, it should be understood that if 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 are involved, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. 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, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, 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 directly connected or indirectly connected through an intermediate medium. It can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] like Figure 1-7 As shown, a single-cavity all-fiber structure variable spot fiber laser comprises a fiber laser light source 8, a transition fiber 3, a multi-clad fiber 4 and an output optical cable 6. The output fiber 1 of the fiber laser light source 8 is connected to the transition fiber 3, the transition fiber 3 is fusedly connected to the multi-clad fiber 4, the multi-clad fiber 4 is fusedly connected to the output optical cable 6, the transition fiber 3 and the multi-clad fiber 4 have the same outer cladding diameter, the multi-clad fiber 4 passes through the hollow telescopic tube 7, the two ends of the multi-clad fiber 4 are exposed outside the hollow telescopic tube 7, the hollow telescopic tube 7 is spirally extended around several circles, and the multi-clad fiber 4 and the hollow telescopic tube 7 remain unchanged in length. The greater the stretching degree of the hollow telescopic tube 7, the greater the bending radius of the multi-clad fiber 4, and the smaller the stretching degree of the hollow telescopic tube 7, the smaller the bending radius of the multi-clad fiber 4. The hollow telescopic tube 7 is flexible and can be flexibly stretched and bent like a rainbow ring toy. The different stretching of the hollow telescopic tube can realize the continuous change of the bending radius of the multi-clad fiber 4.

[0029] For the fiber laser light source, any type of light source in the prior art may be used, which may be a single forward pump input, a single reverse pump input, a forward and reverse pump input, or a MOPA amplification structure.

[0030] A CPS device 2 is set at the connection position between the output optical fiber 1 of the fiber laser light source 8 and the transition optical fiber 3, and a CPS device 5 is set at the connection position between the transition optical fiber 3 and the output optical cable 6 to ensure the stability of the connection and to further filter the output laser of the fiber laser light source 8 and the high-order laser mode generated after the output optical fiber 1 of the fiber laser light source 8 and the transition optical fiber 3 are fused.

[0031] The hollow telescopic tube 7 contains a Teflon sleeve tube inside, which is used to protect the multi-clad optical fiber 4. The multi-clad optical fiber passes through the sleeve tube. The hollow telescopic tube 7 is made of plastic or metal with low laser absorption rate to ensure that it will not affect the normal transmission of the laser. A fixing structure 71 is provided at the port of the multi-clad optical fiber and the hollow telescopic tube. The multi-clad optical fiber coming out of the hollow telescopic tube is fixed, and the length of the multi-clad optical fiber inside the hollow telescopic tube 7 is relatively fixed. Therefore, when the hollow telescopic tube 7 is stretched, the bending radius of the multi-clad optical fiber 4 also changes accordingly. The hollow telescopic tube is surrounded to form multiple circles, forming a rainbow circle structure, which is a spatial structure as a whole. When the rainbow circle structure is compressed to the minimum, the multi-clad optical fiber 4 will have a minimum bending radius. The minimum bending radius of the multi-clad optical fiber 4 is set to be slightly larger than the minimum bending radius of the hollow telescopic tube 7; when the hollow telescopic tube 7 is stretched, from a spatial point of view, the bending radius of the circle formed by the hollow telescopic tube 7 will increase, and the bending radius of the multi-clad optical fiber 4 bound inside will also increase accordingly. When the hollow telescopic tube 7 is compressed, the bending radius of the loop formed becomes smaller, and accordingly, the bending radius of the multi-clad radius 4 bound therein also becomes smaller.

[0032] Focus on reference Figure 3-5 , respectively, are the compression and stretching process of the hollow telescopic tube and the state of being stretched to a greater extent. When it is compressed to the minimum, the bending radius is the smallest. As the stretching increases, the bending radius becomes larger and larger.

[0033] In order to ensure the effectiveness of laser transmission in multi-clad optical fibers, the refractive index of the multi-clad optical fibers needs to be limited accordingly.

[0034] Focus on reference Figure 6As shown, the multi-clad optical fiber 4 includes a core 41, a first cladding 42, a second cladding 43, a third cladding 44, and a fluorine-coated layer 45 arranged in sequence from the inside to the outside. The refractive index of the core 41 is n41, the refractive index of the first cladding 42 is n42, the refractive index of the second cladding 43 is n43, the refractive index of the third cladding 44 is n44, and the refractive index of the fluorine-coated layer 45 is n45. The refractive indices satisfy the following relationship: n41 > n42 > n43 > n44 > n45. The fluorine-coated layer 45 has absorbability for laser light.

[0035] According to the calculation formula of the numerical aperture NA, the numerical aperture NA of the laser in each core layer of the multi-clad optical fiber 4 can be obtained. Let the core layer refractive index of the core be NA41, the core layer refractive index of the first cladding be NA42, the core layer refractive index of the second cladding be NA43, and the core layer refractive index of the third cladding be NA44. The refractive indices of each core layer satisfy the following relationship: NA41 < NA42 < NA43 < NA44. The critical radius of the macro-bending loss of the laser beam transmission inside the optical fiber is related to the NA of the transmission layer; the smaller the NA, the larger the critical radius of the macro-bending loss, that is, the laser is more likely to escape due to the decrease of the optical fiber bending radius, thus reducing the transmission efficiency.

[0036] For the delivery of the laser, the laser output by the fiber laser light source 8 passes through the CPS device 2 to filter out more than 99% of the cladding light, and the laser energy entering the transition optical fiber 3 basically belongs to the core light. The core light in the transition optical fiber 3 enters the core 41 of the multi-clad optical fiber 4. Since n41 > n42, the total reflection condition is satisfied; when the bending radius of the multi-clad optical fiber 4 is greater than the critical radius of the macro-bending loss of its core 41, the laser energy is transmitted in the core 41 with basically no loss; however, as the bending radius of the multi-clad optical fiber 4 gradually decreases to within the macro-bending critical radius of the core 41, a large amount of the laser originally transmitted in the core 41 will escape into the first cladding 42, and since then the laser spot mode has changed; similarly, when the bending radius of the multi-clad optical fiber 4 continues to decrease, the laser in the first cladding 42 will escape into the second cladding 43, and so on.

[0037] The outermost layer of the multi-clad optical fiber 4 is the coating layer 45 that has the ability to absorb laser energy. For the safety of the whole machine optical path, the laser cannot be allowed to enter the coating layer 45 for transmission, and the laser must be blocked in the third cladding 44; when the loop surrounded by the hollow telescopic tube 7 is compressed to the smallest, the bending radius of the internal multi-clad optical fiber 4 must ensure that the laser in the third cladding 44 cannot escape smoothly into the coating layer 45; that is to say, the minimum bending radius of the hollow telescopic tube 7 must be greater than the critical radius of the macro-bending loss of the third cladding 44 to ensure the effective transmission of the laser.

[0038] By limiting the refractive indices of each layer of the multi-clad optical fiber, the transmission efficiency of the laser in the multi-clad optical fiber is maximized.

[0039] The hollow telescopic tube is wound around at least 5 times, and the minimum bending radius of each circle is greater than or equal to 30 mm.

[0040] For the installation of the hollow telescopic tube 8, the hollow telescopic tube is assembled along the arc when stretched, refer to Figure 7 As shown, it is not installed along a straight line, but the stretching direction is set to an arc, which can effectively save space; the laser outputs fiber core light by default, so the rainbow ring structure of the hollow telescopic tube is in a fully stretched state by default.

[0041] The hollow telescopic tube can be stretched as needed to form different bending radii, thereby changing the bending radius of the multi-clad optical fiber, thereby achieving continuous modulation of the laser output mode.

[0042] It should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A single-cavity all-fiber structure variable spot fiber laser, characterized in that: The invention comprises a fiber laser light source, a transition fiber, a multi-clad fiber and an output optical cable. The output optical fiber of the fiber laser light source is connected to the transition fiber, the transition fiber is connected to the multi-clad fiber, and the multi-clad fiber is connected to the output optical cable. The transition fiber and the multi-clad fiber have the same outer cladding diameter. The multi-clad fiber passes through a hollow telescopic tube. Both ends of the multi-clad fiber are exposed outside the hollow telescopic tube. The hollow telescopic tube is spirally extended by wrapping around several circles. When the lengths of the multi-clad fiber and the hollow telescopic tube remain unchanged, the greater the stretching degree of the hollow telescopic tube, the greater the bending radius of the multi-clad fiber, and the smaller the stretching degree of the hollow telescopic tube, the smaller the bending radius of the multi-clad fiber.

2. The single-cavity all-fiber structure variable spot fiber laser according to claim 1, characterized in that: The interior of the hollow telescopic tube includes a liner tube made of Teflon material, and the multi-clad optical fiber passes through the liner tube. The hollow telescopic tube is made of plastic or metal material with low laser absorption rate, and a fixing structure is provided at the port of the multi-clad optical fiber and the hollow telescopic tube.

3. The single-cavity all-fiber structure variable spot fiber laser according to claim 1, characterized in that: CPS devices are respectively arranged at the connection position between the output optical fiber of the optical fiber laser light source and the transition optical fiber, and at the connection position between the transition optical fiber and the output optical cable.

4. The single-cavity all-fiber structure variable spot fiber laser according to claim 1, characterized in that: The multi-clad optical fiber includes a core, a first cladding, a second cladding, a third cladding and a fluorine coating layer. The refractive index of the core is n41, the refractive index of the first cladding is n42, the refractive index of the second cladding is n43, the refractive index of the third cladding is n44, and the refractive index of the fluorine coating layer is n45. The refractive indices satisfy the following relationship: n41>n42>n43>n44>n45.

5. The single-cavity all-fiber structure variable spot fiber laser according to claim 4, characterized in that: Set the core refractive index of the core NA41, the core refractive index of the first cladding NA42, the core refractive index of the second cladding NA43, and the core refractive index of the third cladding NA44. The refractive index of each core layer satisfies the following relationship: NA41 <NA42<NA43<NA44。 6. The single-cavity all-fiber structure variable spot fiber laser according to claim 1, characterized in that: When the hollow telescopic tube is compressed to the minimum, the minimum bending radius of the hollow telescopic tube is greater than the macrobending critical radius of the third cladding.

7. The single-cavity all-fiber structure variable spot fiber laser according to claim 1, characterized in that: The hollow telescopic tube is wound around at least 5 times, and the minimum bending radius of each circle is greater than or equal to 30 mm.

8. The single-cavity all-fiber structure variable spot fiber laser according to claim 1, characterized in that: The hollow telescopic tube is stretched and assembled along an arc when stretched.

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