Optical fiber device with controllable light spots and preparation method thereof

Abstract

The invention relates to a light spot controllable optical fiber device and a preparation method thereof.The light spot controllable optical fiber device comprises an input optical fiber 1 and an output optical fiber 2, the input optical fiber 1 comprises a fiber core, the output optical fiber 2 comprises two fiber cores, one of the two fiber cores of the output optical fiber 2 is a circular fiber core, and the other fiber core of the output optical fiber 2 is a circular fiber core. The other fiber core is an annular fiber core; the input optical fiber 1 is tapered and then is subjected to offset welding with the output optical fiber 2; the output optical fiber 2 is wound, and the winding diameter and the winding number are adjustable. The device is simple in structure and low in cost, the spot ring light spot energy is simpler and more convenient than a regulation and control mode, the output power can reach the kilowatt level, and the application feasibility of the device in the industrial laser welding field is guaranteed.

Description

Technical Field

[0001] The invention relates to the field of laser technology, and in particular to an optical fiber device with controllable light spot and a preparation method thereof. Background Art

[0002] In recent years, laser has been widely used as a processing tool in cutting, welding, additive manufacturing and other fields. High-energy laser beam is an ideal welding heat source. Laser welding with it has the advantages of large penetration depth, large aspect ratio, small heat input, small deformation and easy automation. The welding quality and efficiency are much higher than traditional melting welding. However, for the welding of some highly reflective materials and polar materials, there are many disadvantages when using conventional lasers with Gaussian energy distribution. For example, its energy distribution is uneven, the center energy is strong and the edge energy is weak. When using Gaussian beam focused spot for laser welding, the material is easily melted, gasified and evaporated due to the high laser energy absorbed by the center of the spot, which easily produces defects such as spatter, depressions and cavities; and the laser can only produce one focus at a time, which significantly limits the processing quality, processing accuracy, and processing efficiency. In addition, the energy of the adjustable annular spot is concentrated on the edge ring, and the energy distribution is more uniform. During laser welding, it can effectively avoid problems such as solder spatter and solder point defects caused by excessive intermediate energy. During processing, multiple point welding can be completed at one time, which can not only improve the energy utilization of the laser, but also multiply the processing efficiency.

[0003] In order to improve welding defects such as spatter, hump, and porosity produced during laser welding and to improve welding quality and the cleanliness of the welding surface, a variety of annular beam generation schemes have been proposed at home and abroad, as shown below.

[0004] (1) Adjustable ring spot laser method. With the improvement of fiber coupling technology, domestic and foreign laser manufacturers have successively developed a fiber coupling-based method to form an adjustable ring spot output system. The output fiber of the adjustable ring spot laser is composed of two layers of inner and outer fiber cores. The central fiber and the outer fiber correspond to the point and ring light sources respectively. Each fiber core is coupled with an independent light source module. The wavelength and power of the module can be independently controlled to adjust the laser power corresponding to the point and ring. Compared with other ring spot welding technologies, the adjustable ring spot laser does not require external optical elements for modulation. After the output spot is focused by the lens, a point ring spot can be output at the focal plane, and the point ring power can be adjusted to the optimal parameter state according to different welding application requirements.

[0005] (2) Swinging oscillation method. Compared with other annular spot generation methods, the swinging oscillation method does not require special lasers and external optical element modulation, and has the highest energy utilization efficiency. By program-controlled galvanometer movement, a variety of equivalent light field distributions can be achieved, which can effectively improve various welding defects such as spatter, hump, and porosity, and has a wide range of applications.

[0006] (3) Diffractive optical element method. Based on a single light source and a single diffractive optical element, a shaping design method is used to generate a point light spot in a gear-shaped area with zero phase and a ring light spot in a lens complementary area. This method can achieve the effect of a single diffractive optical element generating a point ring light spot. By adjusting the area of ​​the incident light spot incident on the two phase areas, the energy ratio of the two areas is changed, achieving a continuously adjustable effect of the energy ratio of the point ring light spot.

[0007] The disadvantages of the above scheme are as follows.

[0008] (1) Adjustable annular spot laser method. Compared with single fiber laser, dual fiber coupling requires additional light source module and special fiber structure. At the same time, it requires additional beam combining module to couple the optical fiber input and output ends, which is inconsistent with the current fiber laser interface standard, increasing the cost of laser light source and the complexity of the system.

[0009] (2) Swinging oscillation method. Since the movement is mainly controlled by the galvanometer, the complexity of the optical system is increased, and the processing accuracy is controlled by the motor step accuracy, and the stability is poor. At the same time, the path scanning in space increases the laser welding time, reduces and limits the laser welding rate.

[0010] (3) Diffractive optical element method. Diffractive optical elements are transmissive elements. Due to the limitations of material properties, their applicable power is generally in the kilowatt level. When the power reaches the 10,000-watt level or higher, problems such as thermal lens effect may occur due to excessively high operating temperature, affecting the beam shaping effect. The applicable power of the spatial light modulator is lower, generally below kilowatts, and is usually used in micro-nano laser processing where the required power is not high. It is not suitable for general industrial laser welding.

[0011] In summary, there are two main difficulties in the various methods of generating annular beams: First, if the output of a kilowatt-level spot ring light spot is to be guaranteed, at least two lasers or additional optical elements are required in the optical system, which is complex in structure and high in cost. Second, if the spot ring light spot output is achieved based on a single light source, the output power will be limited to hundreds of watts, which is not suitable for general industrial laser welding.

[0012] In view of this, how to overcome the defects of the above-mentioned prior art and how to solve the above-mentioned technical problems are difficult problems that need to be solved urgently in this technical field. Summary of the invention

[0013] To solve the above technical problems or requirements: if the output of a spot ring light spot with a kilowatt-level power is to be guaranteed, at least two lasers or additional optical elements are required on the optical system to achieve this, which is complex in structure and high in cost; if the spot ring light spot output is achieved based on a single light source, the output power will be limited to hundreds of watts, which cannot be applied to the general industrial laser welding field. The present invention provides a spot-controllable optical fiber device and a preparation method thereof, which has a simple structure, low cost, a simpler control method for the energy ratio of the spot ring light spot, and an output power of up to kilowatts, ensuring its feasibility in the field of industrial laser welding.

[0014] The present invention is achieved in that:

[0015] In a first aspect, the present invention provides an optical fiber device with controllable light spot, comprising an input optical fiber 1 and an output optical fiber 2, wherein the input optical fiber 1 comprises a core, and the output optical fiber 2 comprises two cores, and one of the two cores of the output optical fiber 2 is a circular core and the other is an annular core; the input optical fiber 1 is offset-fused with the output optical fiber 2 after being tapered, so that the laser in the input optical fiber 1 is divided into two parts after being tapered, wherein a part of the fundamental mode and / or multi-mode light remains in the circular core of the output optical fiber 2 for propagation, and the other part contains the fundamental mode light and the higher-order mode light with a larger divergence angle after being tapered, which is confined to propagate in the annular core of the output optical fiber 2; the output optical fiber 2 is wound, and the winding diameter and the number of windings are adjustable.

[0016] In some embodiments, the output optical fiber 2 includes, from the inside to the outside, a first output fiber core 201, a second output fiber core 202, an output inner cladding 203 and an output outer cladding 204, the second output fiber core 202 is arranged adjacent to the first output fiber core 201, the first output fiber core 201 has a circular cross-section, and the second output fiber core 202 has a ring-shaped cross-section.

[0017] In some embodiments, the refractive index of the first output core 201 is greater than the refractive index of the second output core 202 , the refractive index of the second output core 202 is greater than the refractive index of the output inner cladding 203 , and the refractive index of the output inner cladding 203 is greater than the refractive index of the output outer cladding 204 .

[0018] In some embodiments, the input optical fiber 1 includes an input fiber core and an input cladding wrapped around the outer wall of the input fiber core.

[0019] In some embodiments, the input cladding diameter of the input optical fiber 1 before tapering is more than ten times the input core diameter, and the diameter of the first output core 201 is the same as the input core diameter of the input optical fiber 1 before tapering.

[0020] In some embodiments, the diameter of the input cladding of the input optical fiber 1 after tapering is the same as the diameter of the output outer cladding 204 , and the diameter of the input core of the input optical fiber 1 after tapering is smaller than the diameter of the first output core 201 .

[0021] In some embodiments, the coil diameter of the output optical fiber 2 is adjusted by an adjusting device, and the adjusting device includes two metal plates 3 and a plurality of screws 4. The two metal plates 3 are arranged opposite to each other and are penetrated by the plurality of screws 4. The coil portion of the output optical fiber 2 is arranged between the two metal plates 3, so that the distance between the two metal plates 3 can be changed by turning the screws 4, thereby changing the coil diameter of the output optical fiber 2.

[0022] In a second aspect, the present invention provides a method for preparing an optical fiber device with a controllable light spot, which is applied to the optical fiber device with a controllable light spot described in the first aspect, and the method comprises:

[0023] The input optical fiber 1 is tapered, and by controlling the length of the tapered region and the diameter after the tapered region, part of the fundamental mode light in the core of the input optical fiber 1 is excited into a higher-order mode light with a larger divergence angle than the original core;

[0024] After the waist end face of the tapered region of the input optical fiber 1 is cut flat, it is offset-fused with the output optical fiber 2 whose end face is also cut flat. By controlling the axial centerline offset of the core of the input optical fiber 1 and the circular core of the output optical fiber 2, the laser in the input optical fiber 1 after the tapering is divided into two parts, one part of which contains the fundamental mode and / or multi-mode light that remains in the circular core of the output optical fiber 2 for propagation, and the other part contains the fundamental mode light and the higher-order mode light with a larger divergence angle after the tapering, which is confined to the annular core of the output optical fiber 2 for propagation.

[0025] In some embodiments, after offset fusion, the output optical fiber 2 is coiled, and the ratio of laser energy in the circular core and the annular core of the output optical fiber 2 is controlled by adjusting the coil diameter and the number of coils to achieve point ring laser output with different energy ratios or pure ring laser output.

[0026] In some embodiments, the adjustment of the coil diameter of the output optical fiber 2 is achieved by mechanical pressurization, specifically including:

[0027] The output optical fiber 2 is wound in a circle according to a certain initial diameter and placed between two metal plates 3, and screws 4 are respectively passed through the two ends of the metal plates 3;

[0028] The distance between the two metal plates 3 is changed by turning the screw 4, thereby changing the coil diameter of the output optical fiber 2;

[0029] The spot ring energy ratio is tested in real time during the process of adjusting the coil diameter of the output optical fiber 2, thereby realizing a light spot with arbitrary energy ratio output.

[0030] Compared with the prior art, the beneficial effects of the present invention are: providing a controllable optical fiber device and a preparation method thereof, which only requires a single light source, an input optical fiber, and an output optical fiber to achieve the energy output of a spot ring spot, and has a simple structure, is easy to integrate into the fiber laser, has a small size, and is low in cost. In the embodiment of the present invention, the input optical fiber after taper is offset and fused with the output optical fiber, and the output of a spot ring spot or a ring spot can be achieved by adjusting the diameter and number of turns of the coil on the output optical fiber, and the output of a spot with different energy ratios of the spot ring can also be achieved, and the shape of the output beam and the energy control method are simpler; and because the energy output of the fiber laser light source itself can reach the kilowatt level, the generated spot ring laser or pure ring laser can also reach the kilowatt level of energy output, ensuring its feasibility in the field of industrial laser welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic structural diagram of an optical fiber device with controllable light spot provided by an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of the cross section and refractive index of an output optical fiber provided in an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of an output optical fiber before compression provided by an embodiment of the present invention;

[0035] Figure 4 A schematic diagram of an output optical fiber after compression provided by an embodiment of the present invention;

[0036] Figure 5 A flow chart of a method for preparing an optical fiber device with controllable light spot provided by an embodiment of the present invention;

[0037] Figure 6 A schematic diagram of test results of non-offset welding provided by an embodiment of the present invention;

[0038] Figure 7 A schematic diagram of the test results of welding after a 10um offset provided in an embodiment of the present invention;

[0039] Figure 8 A schematic diagram of the test results of welding after a 20um offset provided in an embodiment of the present invention;

[0040] Fig. 9 A schematic diagram of input optical fiber taper region parameters provided by an embodiment of the present invention;

[0041] Fig.10 A schematic diagram of the offset fusion point of the input optical fiber and the output optical fiber provided in an embodiment of the present invention;

[0042] Fig.11 A schematic diagram of the winding of the output optical fiber provided in an embodiment of the present invention;

[0043] Fig.12 A schematic diagram of horizontal transmission of light paths in output optical fibers provided by an embodiment of the present invention;

[0044] Fig.13 A schematic cross-sectional diagram of the laser spot distribution before and after laser beam shaping provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as open inclusion, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "examples", "specific examples" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner, that is, although they may be carried in the embodiments or examples of the above terms due to reasons such as the order and position of appearance, it is not limited to that they can be carried in combination by one embodiment or example.

[0046] In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "up", "down", "left", "right", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0047] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0048] It should be noted that, if there is no conflict, the various features in the embodiments of the present invention can be combined with each other, all within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by technicians in the technical field of the present invention. The terms and directions used in this specification are only for the purpose of describing specific implementation methods and are not intended to limit the present invention.

[0049] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0050] Example 1

[0051] refer to Figure 1 As shown, Embodiment 1 of the present invention provides a controllable optical fiber device with a light spot, including an input optical fiber 1 and an output optical fiber 2, wherein the input optical fiber 1 includes a core, the output optical fiber 2 includes two cores, and one of the two cores of the output optical fiber 2 is a circular core and the other is a ring core; the input optical fiber 1 is offset-fused with the output optical fiber 2 after being tapered, so that the laser in the input optical fiber 1 is divided into two parts after being tapered, wherein a part of the fundamental mode and / or multi-mode light is retained in the circular core of the output optical fiber 2 for propagation, and the other part contains the fundamental mode light and the high-order mode light with a larger divergence angle after being tapered and is confined to the ring core of the output optical fiber 2 for propagation; the output optical fiber 2 is wound, and the winding diameter and the number of windings are adjustable. Through the above-mentioned setting, a controllable spot ring light spot can be generated by a single light source, so as to realize a controllable optical fiber device with a light spot, which has a simple structure, low cost, and a simpler control method for the energy ratio of the spot ring light spot, and the output power can reach the kilowatt level, ensuring its feasibility in the field of industrial laser welding.

[0052] refer to Figure 2 As shown, in some embodiments, the output optical fiber 2 is a coaxial double-core optical fiber with a special structure. Specifically, the output optical fiber 2 includes a first output core 201, a second output core 202, an output inner cladding 203, and an output outer cladding 204 from the inside to the outside. The second output core 202 is arranged adjacent to the first output core 201. The cross section of the first output core 201 is circular, and the cross section of the second output core 202 is annular. In some embodiments, the refractive index n1 of the first output core 201 is greater than the refractive index n2 of the second output core 202, the refractive index n2 of the second output core 202 is greater than the refractive index n3 of the output inner cladding 203, and the refractive index n3 of the output inner cladding 203 is greater than the refractive index n4 of the output outer cladding 204.

[0053] In some embodiments, the input optical fiber 1 includes an input core and an input cladding wrapped around the outer wall of the input core. After the input optical fiber 1 is tapered, it is offset-fused with the output optical fiber 2. After the offset-fusion, it is wound around the output optical fiber 2 with the same diameter to output a laser with a controllable spot ring. In some embodiments, the input cladding diameter of the input optical fiber 1 before tapering is more than ten times the input core diameter, and the diameter of the first output core 201 is the same as the input core diameter of the input optical fiber 1 before tapering. In some embodiments, the diameter of the input cladding of the input optical fiber 1 after tapering is the same as the diameter of the output outer cladding 204, and the diameter of the input core of the input optical fiber 1 after tapering is smaller than the diameter of the first output core 201.

[0054] refer to Figure 3 and Figure 4 As shown, in some embodiments, the coil diameter of the output optical fiber 2 is adjusted by an adjusting device, and the adjusting device includes two metal plates 3 and a plurality of screws 4. The two metal plates 3 are arranged opposite to each other and are penetrated by the plurality of screws 4. The coil portion of the output optical fiber 2 is arranged between the two metal plates 3, so that the distance between the two metal plates 3 can be changed by turning the screws 4, thereby changing the coil diameter of the output optical fiber 2.

[0055] In summary, the embodiment of the present invention provides a fiber optic device with controllable light spot, which only needs a single light source, an input optical fiber, and an output optical fiber to realize the energy output of a spot ring light spot, has a simple structure, is easy to integrate into the fiber laser, has a small size, and is low in cost. The embodiment of the present invention offset-splices the input optical fiber after taper and the output optical fiber, and realizes the output of a spot ring light spot or a ring light spot by adjusting the diameter and number of turns of the coil on the output optical fiber, and can also realize the output of a spot with different energy ratios of the spot ring, and the shape of the output beam and the energy control method are simpler; and because the energy output of the fiber laser light source itself can reach the kilowatt level, the generated spot ring laser or pure ring laser can also reach the kilowatt level of energy output, ensuring its feasibility in the field of industrial laser welding.

[0056] Example 2

[0057] Based on Example 1, the present invention also provides a method for preparing an optical fiber device with controllable light spot, referring to Figure 5 As shown, the method includes the following steps.

[0058] Step 100: Taper the input optical fiber 1, and by controlling the length of the tapered region and the diameter after taper, part of the fundamental mode light in the core of the input optical fiber 1 is excited into a higher-order mode light with a larger divergence angle than the original core.

[0059] Step 200: After the waist end face of the tapered region of the input optical fiber 1 is cut flat, offset fusion splicing is performed with the output optical fiber 2 whose end face is also cut flat, and by controlling the axis centerline offset of the core of the input optical fiber 1 and the circular core of the output optical fiber 2, the laser in the input optical fiber 1 after the tapering is divided into two parts, one part of which is the fundamental mode and / or multimode light remaining in the circular core of the output optical fiber 2 for propagation, and the other part contains the fundamental mode light and the higher-order mode light with a larger divergence angle after the tapering, which is confined to propagate in the annular core of the output optical fiber 2. Offset fusion splicing has a mode scrambling effect, which can make the ring layer light homogenized, the energy evenly distributed, and the core light is easier to enter the ring layer.

[0060] Step 300: After the offset fusion, the output optical fiber 2 is coiled, and the ratio of the laser energy in the circular core and the ring core of the output optical fiber 2 is controlled by adjusting the coil diameter and the number of coils to achieve point ring laser output with different energy ratios or pure ring laser output.

[0061] refer to Figure 3 and Figure 4 As shown, in some embodiments, the adjustment of the coil diameter of the output optical fiber 2 is achieved by mechanical pressurization, specifically including: the output optical fiber 2 is coiled according to a certain initial diameter and then placed between two metal plates 3, and the two ends of the metal plates 3 are respectively penetrated by screws 4; the distance between the two metal plates 3 is changed by turning the screws 4, thereby changing the coil diameter of the output optical fiber 2; in the process of adjusting the coil diameter of the output optical fiber 2, the point ring energy ratio is tested in real time, thereby realizing a light spot with arbitrary energy ratio output, and the adjustment process is simple and fast.

[0062] The following experiment explains the mode disturbance effect of offset welding: a laser with a core diameter of 50um and a numerical aperture of 0.22 is welded to an optical fiber with a core diameter of 100um and a numerical aperture of 0.22 in three different conditions: "non-offset welding", "core axis offset welding with 10um centerline", and "core axis offset welding with 20um centerline". The following are the corresponding results on the output optical fiber with a core diameter of 100um: Figure 6 , Figure 7 and Figure 8 Three light spots with different energy distributions are shown.

[0063] Figure 6 In the output spot measurement results, it can be seen from the spot intensity cross-section curve in the x and y directions of the spot at the waist area that the energy distribution curve fluctuates greatly, the energy values ​​at each point vary greatly, and the spot energy distribution is uneven. Figure 7 This is the output spot energy diagram after the welding after the offset of 10um. It can be seen that although the fluctuation of the spot intensity curve in the y direction is still large, the fluctuation of the spot intensity curve in the x direction tends to be gentle, and the energy value difference at each point is small. Figure 8From the output spot energy diagram after fusion with a 20um offset, it can be seen that the fluctuation of the spot energy distribution curves in the x and y directions is small, the energy values ​​of each point within the entire core diameter range are slightly different, and the spot is more uniform.

[0064] It can be concluded that the output spot energy distribution after the two offset weldings is more uniform than that of the non-offset welding, and the output spot energy distribution after the 20um offset welding is more uniform than that after the 10um offset welding. Therefore, when welding, if the input optical fiber and the output optical fiber are offset on the axis of the fiber cores by a certain amount before welding, the spot energy distribution of the input laser can be changed, and the offset welding has the effect of interfering with the input light mode.

[0065] In summary, the embodiment of the present invention provides a method for preparing an optical fiber device with controllable light spot, which only requires a single light source, an input optical fiber, and an output optical fiber to achieve the energy output of a spot ring light spot. The structure is simple, easy to integrate into the fiber laser, small in size, and low in cost. The embodiment of the present invention offset-splices the input optical fiber after taper and the output optical fiber, and achieves the output of a spot ring light spot or a ring light spot by adjusting the diameter and number of turns of the coil on the output optical fiber. At the same time, the output of a spot with different energy ratios of the spot ring can also be achieved, and the shape of the output beam and the energy control method are simpler; and because the energy output of the fiber laser light source itself can reach the kilowatt level, the generated spot ring laser or pure ring laser can also reach the kilowatt level of energy output, ensuring its feasibility in the field of industrial laser welding.

[0066] Example 3

[0067] Based on the above-mentioned Embodiment 1 and Embodiment 2, this Embodiment 3 further describes the embodiment of the present invention in more detail through a specific example.

[0068] Figure 1 The schematic diagram of the structure of a fiber optic device with controllable light spot provided in an embodiment of the present invention includes an input fiber 1 and an output fiber 2. The input fiber 1 includes an input fiber core and an input cladding wrapped around the outer wall of the input fiber core. The output fiber 2 is a coaxial dual-core fiber with a special structure, which is divided into four layers from the inside to the outside. The refractive index of the first output fiber core 201 is n1, the refractive index of the second output fiber core 202 is n2, the refractive index of the output inner cladding 203 is n3, and the refractive index of the output outer cladding 204 is n4. The cross-sectional view of the output fiber 2 and the refractive index distribution are shown in FIG. Figure 2As shown: n1>n2>n3>n4. After the input optical fiber 1 is tapered, the diameters of the optical fiber core and cladding are proportionally reduced, resulting in a change in the laser mode field distribution in the input optical fiber core, and part of the fundamental mode light is excited to be a higher-order mode light with a larger divergence angle than the original. The waist end face of the input optical fiber 1 after tapering is cut flat and offset-spliced ​​with the output optical fiber 2 whose end face is also cut flat. By controlling the axis centerline offset e of the core of the input optical fiber 1 and the core of the output optical fiber 2 during the fusion splicing, a part of the fundamental mode light in the input optical fiber 1 after tapering is retained in the first output core 201 for propagation, and the other part, including the fundamental mode light and the higher-order mode light with a larger divergence angle after tapering, is confined to propagate in the second output core 202 of the output optical fiber. The output optical fiber 2 is coiled, and the ratio of the laser energy in the first output core 201 and the second output core 202 of the output optical fiber 2 is controlled by adjusting the diameter of the coil and the number of coils, so as to achieve point ring laser output or pure ring laser output with different energy ratios. For reference, see the schematic diagram of horizontal transmission of the optical path in the output optical fiber. Fig.12 shown.

[0069] Specifically, in some embodiments, the core diameter of the input optical fiber 1 is 14um, the cladding diameter is 250um, and the numerical aperture is 0.07. The diameter and refractive index of the first output core 201 of the output optical fiber 2 are 14um and 1.53, respectively, the diameter and refractive index of the second output core 202 are 100um and 1.5, respectively, the diameter and refractive index of the output inner cladding 203 are 120um and 1.47, respectively, and the diameter and refractive index of the output outer cladding 204 are 200um and 1.41, respectively. The numerical aperture of the first output core 201 of the output optical fiber 2 is 0.07, and the numerical aperture of the second output core 202 is 0.22.

[0070] In some embodiments, reference Fig. 9 As shown, the core and cladding diameters D2 of the input optical fiber 1 after tapering are 11.2 um and 200 um respectively, and the tapered length L of the tapered region is 15 mm.

[0071] In some embodiments, reference Fig.10 As shown, the input optical fiber 1 is cut flat at the waist area of ​​the tapered region and offset-fused with the output optical fiber 2 which has also been cut flat at the end face. The axial centerline offset e of the core of the input optical fiber 1 and the core of the output optical fiber 2 is 2.5 um.

[0072] In some embodiments, reference Fig.11 As shown in the figure, the diameter d and number of the coils on the output optical fiber 2 are 10 cm and 3 coils respectively. At this time, the output light spot of the output optical fiber 2 is a point ring light spot with a core-ring energy ratio of 3:1. For example, the light spot originally generated by the input optical fiber 1 is referenced Fig.13 As shown in A in FIG. 1 , after the above settings, the schematic diagram of the dot ring light spot in the output optical fiber 2 is as follows Fig.13 As shown in B.

[0073] In some embodiments, if the diameter and number of the coils on the output optical fiber 2 are 5 cm and 5 coils respectively, then the output light spot of the output optical fiber 2 is a point ring light spot with a core-to-ring energy ratio of 1:3. Fig.13 As shown in A in the figure, after the above settings, the schematic diagram of the dot ring light spot in the output optical fiber is as follows Fig.13 As shown in B.

[0074] Example 4

[0075] Based on the above-mentioned Embodiment 1 and Embodiment 2, this Embodiment 4 further describes the embodiment of the present invention in more detail through a specific example.

[0076] Figure 1 The schematic diagram of the structure of a fiber optic device with controllable light spot provided in an embodiment of the present invention includes an input fiber 1 and an output fiber 2. The input fiber 1 includes an input fiber core and an input cladding wrapped around the outer wall of the input fiber core. The output fiber 2 is a coaxial dual-core fiber with a special structure, which is divided into four layers from the inside to the outside. The refractive index of the first output fiber core 201 is n1, the refractive index of the second output fiber core 202 is n2, the refractive index of the output inner cladding 203 is n3, and the refractive index of the output outer cladding 204 is n4. The cross-sectional view of the output fiber 2 and the refractive index distribution are shown in FIG. Figure 2 As shown: n1>n2>n3>n4. After the input optical fiber 1 is tapered, the diameters of the optical fiber core and cladding are proportionally reduced, resulting in a change in the laser mode field distribution in the input optical fiber core, and part of the fundamental mode light is excited to be a higher-order mode light with a larger divergence angle than the original. The waist end face of the input optical fiber 1 after tapering is cut flat and offset-spliced ​​with the output optical fiber 2 whose end face is also cut flat. By controlling the axis centerline offset e of the core of the input optical fiber 1 and the core of the output optical fiber 2 during the fusion splicing, a part of the fundamental mode light in the input optical fiber 1 after tapering is retained in the first output core 201 for propagation, and the other part, including the fundamental mode light and the higher-order mode light with a larger divergence angle after tapering, is confined to propagate in the second output core 202 of the output optical fiber. The output optical fiber 2 is coiled, and the ratio of the laser energy in the first output core 201 and the second output core 202 of the output optical fiber 2 is controlled by adjusting the diameter of the coil and the number of coils, so as to achieve point ring laser output or pure ring laser output with different energy ratios. For reference, see the schematic diagram of horizontal transmission of the optical path in the output optical fiber. Fig.12 shown.

[0077] Specifically, in some embodiments, the core diameter of the input optical fiber 1 is 20um, the cladding diameter is 250um, and the numerical aperture is 0.065. The diameter and refractive index of the first output core 201 of the output optical fiber 2 are 20um and 1.55, respectively, the diameter and refractive index of the second output core 202 are 100um and 1.51, respectively, the diameter and refractive index of the output inner cladding 203 are 120um and 1.49, respectively, and the diameter and refractive index of the output outer cladding 204 are 200um and 1.43, respectively. The numerical aperture of the first output core 201 of the output optical fiber 2 is 0.065, and the numerical aperture of the second output core 202 is 0.22.

[0078] In some embodiments, reference Fig. 9 As shown, the core and cladding diameters D2 of the input optical fiber 1 after tapering are 16 um and 200 um respectively, and the tapered length L of the tapered region is 15 mm.

[0079] In some embodiments, reference Fig.10 As shown, the input optical fiber 1 is cut flat at the waist area of ​​the tapered region and offset-fused with the output optical fiber 2 which has also been cut flat at the end face. The axial centerline offset e of the core of the input optical fiber 1 and the core of the output optical fiber 2 is 11 um.

[0080] In some embodiments, reference Fig.11 As shown in the figure, the diameter d and number of the coils on the output optical fiber 2 are 8 cm and 2 coils respectively. At this time, the output light spot of the output optical fiber 2 is a point ring light spot with a core-ring energy ratio of 1.5:1. For example, the light spot originally generated by the input optical fiber 1 is referenced Fig.13 As shown in A in the figure, after the above settings, the schematic diagram of the dot ring light spot in the output optical fiber is as follows Fig.13 As shown in B.

[0081] In some embodiments, if the diameter and number of the circles on the output optical fiber 2 are 3 cm and 5 circles respectively, then the light spot output by the output optical fiber 2 is a ring-shaped light spot. Fig.13 As shown in A in the figure, after the above settings, the schematic diagram of the dot ring light spot in the output optical fiber is as follows Fig.13 As shown in C.

[0082] 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 them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical fiber device with controllable light spot, characterized in that: The invention comprises an input optical fiber (1) and an output optical fiber (2), wherein the input optical fiber (1) comprises a core, and the output optical fiber (2) comprises two cores, wherein one of the two cores of the output optical fiber (2) is a circular core and the other is an annular core; the input optical fiber (1) is offset-fused with the output optical fiber (2) after being tapered, so that the laser in the input optical fiber (1) is divided into two parts after being tapered, wherein a part of the fundamental mode and / or multi-mode light is retained in the circular core of the output optical fiber (2) for propagation, and the other part contains the fundamental mode light and the higher-order mode light with a larger divergence angle after being tapered and is confined to the annular core of the output optical fiber (2) for propagation; the output optical fiber (2) is wound in a circle, and the diameter and number of the windings are adjustable.

2. The optical fiber device with controllable light spot according to claim 1, characterized in that: The output optical fiber (2) comprises, from the inside to the outside, a first output fiber core (201), a second output fiber core (202), an output inner cladding (203) and an output outer cladding (204); the second output fiber core (202) is arranged adjacent to the first output fiber core (201); the first output fiber core (201) has a circular cross section, and the second output fiber core (202) has a ring cross section.

3. The optical fiber device with controllable light spot according to claim 2, characterized in that: The refractive index of the first output fiber core (201) is greater than the refractive index of the second output fiber core (202), the refractive index of the second output fiber core (202) is greater than the refractive index of the output inner cladding (203), and the refractive index of the output inner cladding (203) is greater than the refractive index of the output outer cladding (204).

4. The optical fiber device with controllable light spot according to claim 2, characterized in that: The input optical fiber (1) comprises an input fiber core and an input cladding wrapped around the outer wall of the input fiber core.

5. The optical fiber device with controllable light spot according to claim 4, characterized in that: The input cladding diameter of the input optical fiber (1) before tapering is more than ten times the input core diameter, and the diameter of the first output core (201) is the same as the input core diameter of the input optical fiber (1) before tapering.

6. The optical fiber device with controllable light spot according to claim 4, characterized in that: The diameter of the input cladding of the input optical fiber (1) after tapering is the same as the diameter of the output outer cladding (204), and the diameter of the input core of the input optical fiber (1) after tapering is smaller than the diameter of the first output core (201).

7. The optical fiber device with controllable light spot according to any one of claims 1 to 6, characterized in that: The coil diameter of the output optical fiber (2) is adjusted by an adjusting device, the adjusting device comprising two metal plates (3) and a plurality of screws (4), the two metal plates (3) being arranged opposite to each other and both being penetrated by the plurality of screws (4), the coil portion of the output optical fiber (2) being arranged between the two metal plates (3), so that the distance between the two metal plates (3) can be changed by turning the screws (4), thereby changing the coil diameter of the output optical fiber (2).

8. A method for preparing an optical fiber device with controllable light spot, applied to the optical fiber device with controllable light spot according to any one of claims 1 to 7, characterized in that: include: The input optical fiber (1) is tapered, and by controlling the length of the tapered region and the diameter after the tapered region, part of the fundamental mode light in the core of the input optical fiber (1) is excited into a higher-order mode light with a larger divergence angle than the original core; After the waist end face of the tapered region of the input optical fiber (1) is cut flat, it is offset-fused with the output optical fiber (2) whose end face is also cut flat. By controlling the axis centerline offset of the input optical fiber (1) core and the circular core of the output optical fiber (2), the laser in the input optical fiber (1) after the tapering is divided into two parts, one part of which contains fundamental mode and / or multi-mode light remaining in the circular core of the output optical fiber (2) for propagation, and the other part contains fundamental mode light and higher-order mode light with a larger divergence angle after the tapering, which is confined to the annular core of the output optical fiber (2) for propagation.

9. The method for preparing an optical fiber device with controllable light spot according to claim 8, characterized in that: After the offset fusion splicing, the output optical fiber (2) is coiled, and the ratio of laser energy in the circular core and the ring core of the output optical fiber (2) is controlled by adjusting the coil diameter and the number of coils, so as to achieve point ring laser output or pure ring laser output with different energy ratios.

10. The method for preparing a fiber optic device with controllable light spot according to claim 9, characterized in that: The adjustment of the coil diameter of the output optical fiber (2) is achieved by mechanical pressure, specifically including: The output optical fiber (2) is coiled according to a certain initial diameter and then placed between two metal plates (3), and the two ends of the metal plates (3) are respectively penetrated by screws (4); The distance between the two metal plates (3) is changed by turning the screw (4), thereby changing the winding diameter of the output optical fiber (2); In the process of adjusting the coil diameter of the output optical fiber (2), the spot ring energy ratio is tested in real time, thereby realizing a light spot with an arbitrary energy ratio output.

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