Optical fiber device, preparation method, laser and processing equipment

Abstract

The invention discloses an optical fiber device and a preparation method thereof, a laser and equipment, the optical fiber device comprises an output optical fiber, a graded-index optical fiber and an output head which are connected in sequence, and the output optical fiber comprises a fiber core and a cladding and is used for outputting a point loop light beam; the graded-index optical fiber is used for adjusting the light path of the point-loop light beam to adjust the divergence angle of the inner and outer-loop light beams; and the output head is used for outputting the adjusted light beam. By combining the inherent beam shaping characteristic of the graded-index optical fiber, effective and flexible regulation and control of the divergence angle of the output light are realized, and the device is especially suitable for a multi-wavelength laser output scene, and has the advantages of simple structure, low cost and high stability.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of laser technology, in particular to a fiber device with adjustable output light divergence angle, a preparation method, a laser and a processing equipment. BACKGROUND

[0002] Laser has become the mainstream choice in industrial processing and other fields due to its excellent beam quality, high efficiency and stability. However, in these applications, the precise control of the output laser divergence angle is crucial, directly affecting the effect of cutting, drilling, welding and other processes.

[0003] Currently, the mainstream method to control the output divergence angle of the laser is to integrate optical lens groups in the laser output head, such as collimation focusing systems or variable expansion systems. The collimation focusing system changes the spot size on the working distance by adjusting the focal point position, but it has problems such as fixed focal depth, limited working distance, lens pollution and thermal lens effect. The variable expansion system directly adjusts the divergence angle by changing the beam diameter, but its structure is complex, the cost is high, it may introduce aberration and the response speed is relatively slow.

[0004] Therefore, there is an urgent need in the art for a new optical device with simple structure, low cost and effective control of the output light divergence angle. SUMMARY

[0005] Based on this, the present application provides a fiber device, a preparation method, a laser and a processing equipment, which has simple structure, low cost and can effectively control the output light divergence angle.

[0006] In a first aspect, the present application provides a fiber device, comprising sequentially connected:

[0007] an output fiber comprising a core and a cladding, for outputting a point ring beam;

[0008] a graded-index fiber for adjusting the optical path of the point ring beam to achieve adjustment of the divergence angle of the inner and outer ring beams;

[0009] an output head for outputting the adjusted beam.

[0010] As a preferred scheme, the length range of the graded-index fiber satisfies:

[0011] L=(n+1 / 4)×P; n≥0, n is an integer;

[0012] wherein L is the length; p is the period, which refers to the length of the fiber traveled by the beam when completing a complete oscillation cycle along a sinusoidal trajectory in the fiber; n is the number of complete oscillation cycles in the graded-index fiber; the length units of L and P are mm.

[0013] As a preferred solution, the output fiber comprises a core and a first cladding layer; the first cladding layer comprises a first taper structure, and the first taper structure is used to control the size of the output beam divergence angle of the output fiber;

[0014] Or, the output fiber comprises a core, a first cladding layer and a second cladding layer; the second cladding layer comprises a first taper structure, and the first taper structure is used to control the size of the output beam divergence angle of the output fiber;

[0015] Or, the output fiber comprises a core, a first cladding layer, a second cladding layer and an outer cladding layer; the outer cladding layer comprises a first taper structure, and the first taper structure is used to control the size of the output beam divergence angle of the output fiber.

[0016] As a preferred solution, the outer cladding layer comprises a third cladding layer and a coating layer, and the third cladding layer close to at least part of the area of the graded-index fiber comprises the first taper structure, or the outer cladding layer comprises a third cladding layer, a fourth cladding layer and a coating layer, and the fourth cladding layer close to at least part of the area of the graded-index fiber comprises the first taper structure.

[0017] As a preferred solution, the graded-index fiber comprises a graded core and an outer cladding layer, and the input end of the graded-index fiber close to at least part of the area of the output fiber comprises a second taper structure, and / or the output end of the graded-index fiber close to at least part of the area of the output head comprises a third taper structure.

[0018] As a preferred solution, the output end face shape of the output head comprises a plane, a spherical surface or an arc surface.

[0019] As a preferred solution, the core diameter of the graded-index fiber is greater than the diameter of the outer cladding layer of the output fiber after taper processing.

[0020] Based on the same inventive concept, in a second aspect, the embodiments of the present application further provide a preparation method of a fiber device, for preparing the fiber device provided in the first aspect, comprising:

[0021] Providing an output fiber, the output fiber comprises a core and at least two cladding layers, and is used to output a point ring beam;

[0022] Providing a graded-index fiber, the graded-index fiber is used to adjust the optical path of the point ring beam to achieve adjustment of the divergence angle of the inner and outer ring beams;

[0023] Providing an output head, the output head is used to output the adjusted beam;

[0024] connecting an output end of the output fiber with an input end of the graded-index fiber, and connecting an output end of the graded-index fiber with an input end of the output head.

[0025] Preferably, the output fiber is prepared by the steps of:

[0026] The outer cladding of the output end of the output fiber is tapered to form a tapered output end, and the output end is cut to a desired diameter by scanning.

[0027] The graded-index fiber is prepared by the steps of:

[0028] The outer cladding of the input end and the output end of the graded-index fiber is tapered to form tapered input and output ends, and the input and output ends are cut to a desired diameter by scanning.

[0029] The connecting step includes:

[0030] The output end of the tapered output fiber is fused with the input end of the graded-index fiber, and the output end of the graded-index fiber is fused with the input end of the output head.

[0031] The fused assembly is installed in an external housing.

[0032] Based on the same inventive concept, in a third aspect, the embodiments of the present application further provide a laser, comprising the output fiber device with adjustable output light divergence angle provided in the first aspect.

[0033] Based on the same inventive concept, in a fourth aspect, the embodiments of the present application further provide a laser processing device, comprising the laser provided in the third aspect.

[0034] In summary, the present application provides a fiber device, which comprises an output fiber, a graded-index fiber and an output head in sequence. The output fiber comprises a core and a cladding, and is used for outputting a point ring light beam. The graded-index fiber is used for adjusting the light path of the point ring light beam to achieve adjustment of the divergence angle of the inner and outer ring light beams. The output head is used for outputting the adjusted light beam.

[0035] The core of the application is that by the inherent beam shaping characteristics of the graded index fiber, the point ring beam output by the output fiber is modulated, the divergence angles of the output light, the inner and outer ring beams are effectively and flexibly regulated, the convergence of the inner and outer ring beams is more regular and symmetrical, a clear and explicit ring boundary can be formed, the size and shape of the focused spot are more regular, the spot has high precision and uniform light intensity distribution, the local power density caused by the concentration of the light field is reduced, and the optical loss caused by the nonlinear effect is reduced, the mode interference between beams with different numerical apertures can be reduced, the spot is more stable, and the device has the advantages of simple structure, low cost and high stability. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A schematic diagram of a fiber device provided by the application example is shown in the figure;

[0037] Figure 2 A structural schematic diagram of an output fiber provided by the application example is shown in the figure;

[0038] Figure 3 A structural schematic diagram of another output fiber provided by the application example is shown in the figure;

[0039] Figure 4 A structural sectional view of another output fiber provided by the application example is shown in the figure;

[0040] Figure 5 A structural schematic diagram of an output fiber provided by the application example is shown in the figure;

[0041] Figure 6 A structural schematic diagram of a graded index fiber provided by the application example is shown in the figure;

[0042] Figure 7 A refractive index distribution and structural schematic diagram of a graded index fiber provided by the application example is shown in the figure;

[0043] Figure 8 A light propagation schematic diagram of a graded index fiber provided by the application example is shown in the figure;

[0044] Figure 9 A refractive index distribution and structural schematic diagram of another graded index fiber provided by the application example is shown in the figure;

[0045] Figure 10 A schematic diagram of a spot at the beam waist of an output beam of a fiber device provided by the application example is shown in the figure;

[0046] Figure 11 A schematic diagram of a spot at the beam waist of an output beam of a fiber device provided by the application example is shown in the figure;

[0047] Figure 12 A schematic diagram of a preparation method of a fiber device provided by the application example is shown in the figure.

[0048] In the drawings:

[0049] 1, output fiber; 2, graded-index fiber; 3, output head; 4, outer shell; 5, core; 6, first cladding layer; 7, second cladding layer; 8, third cladding layer; 9, fourth cladding layer; 10, coating layer; 21, graded core; 22, outer cladding layer; 23, second coating layer; n1 is the core refractive index of the graded-index fiber; n2 is the first cladding layer refractive index of the graded-index fiber; is the core wavelength of the output fiber; is the cladding wavelength of the output fiber; V1 is the first taper structure; V2 is the second taper structure; V3 is the third taper structure. DETAILED DESCRIPTION

[0050] The application will be further described below in conjunction with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the application, but not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings, but not all the structures. Various modifications and changes can be made in the application without departing from the spirit or scope of the application, which will be apparent to those skilled in the art. Thus, the application is intended to cover the modifications and variations of the application that fall within the scope of the corresponding claims (claimed technical solutions) and their equivalents. It should be noted that the embodiments provided by the application can be combined with each other without contradiction.

[0051] Wherein, the core wavelength is not the light emitted by the core itself, but refers to the wavelength of the light that can be transmitted in the core of the optical fiber, and the cladding wavelength refers to the wavelength of the light that can be transmitted in the cladding of the optical fiber.

[0052] Figure 1 is a schematic diagram of an optical fiber device provided by the application, Figure 2 is a structural schematic diagram of an output fiber provided by the application, Figure 4 is another structural sectional view of an output fiber provided by the application, Figure 6 is a structural schematic diagram of a graded-index fiber provided by the application, Figure 7 is a refractive index distribution and structural schematic diagram of a graded-index fiber provided by the application, Figure 8 is a light propagation schematic diagram of a graded-index fiber provided by the application, Figure 9 is another refractive index distribution and structural schematic diagram of a graded-index fiber provided by the application. Reference Figure 1The embodiment of the present application provides a kind of optical fiber device 100, which includes output optical fiber 1, graded-index optical fiber 2 and output head 3 connected in sequence.The output optical fiber 1, graded-index optical fiber 2 and output head 3 are collectively encapsulated in an external shell 4.It is referred to Figure 2 The output optical fiber 1 includes core 5 and cladding.Exemplarily, the number of cladding of output optical fiber 1 can be 1, 2, 3, 4, 5 and so on, in the embodiment of the present application Figure 2 In the embodiment of the present application, the output optical fiber 1 is composed of core 5 and four layers of cladding, which are first cladding 6 covering core 5, second cladding 7 covering first cladding 6, third cladding 8 covering second cladding 7 and fourth cladding 9 covering third cladding 8. Figure 5 In the embodiment of the present application, the output optical fiber 1 is composed of core 5 and first cladding 6 covering core 5.Each cladding has a cross-sectional shape of a ring, which can be a circular ring, an elliptical ring, a triangular ring, a rectangular ring or a racetrack-shaped ring, etc., which can be designed according to the actual optical fiber structure in specific implementation.

[0053] The output optical fiber 1 is used to output a point-ring light beam.

[0054] In addition, the point-ring light beam refers to the cross-sectional pattern of the beam, which has a plurality of concentric rings with a bright spot in the middle.It should be noted that in practice, the beam is not completely regular during transmission, and the shape boundary of the ring-shaped spot is not necessarily clear and regular, which is not limited in the embodiment of the present application.

[0055] In the embodiment of the present application, the graded-index optical fiber 2 is connected with the output optical fiber 1, exemplarily by fusion, welding mechanical connection, etc..The graded-index optical fiber (GRIN optical fiber, Graded-Index optical fiber) refers to an optical fiber with a gradually changing refractive index to significantly optimize the performance of multimode transmission, specifically, the core refractive index gradually changes from the center to the edge, such as gradually decreasing;The cladding refractive index is a uniform fixed value.

[0056] By the inherent beam shaping characteristics of the graded-index optical fiber, the point-ring light beam output by the output optical fiber 1 can be modulated, the divergence angles of the output light, inner and outer ring light beams can be effectively and flexibly controlled, the convergence of the inner and outer ring light beams is more regular and symmetrical, a clear and explicit ring boundary can be formed, the size and shape of the focused spot are more regular, the spot has high precision and uniform light intensity distribution, the local power density caused by light field concentration can be reduced, thereby reducing the optical loss caused by nonlinear effects, and the mode interference between light beams with different numerical apertures can be reduced, so that the spot is more stable.

[0057] The output head 3 is connected with the graded-index fiber 2, the output head 3 can adopt a quartz output head, the material has a very high laser damage threshold, excellent spectral transmittance, very high thermal stability and low thermal expansion coefficient, etc., which can realize stable and efficient output of the adjusted point ring light beam.

[0058] On the basis of the above-mentioned embodiments, with reference to Figure 1 and Figure 2 , the output end of the output fiber 1 and the two ends of the graded-index fiber 2 are tapered, the input end of the graded-index fiber can increase the receiving angle of the optical waveguide, so that more incident angle laser can be transmitted in the optical waveguide, thereby improving the light collecting capacity of the optical waveguide, shaping the light beam, and reducing the loss during the fusion of the output fiber 1 through mode field matching, and the output end of the graded-index fiber can further adjust the divergence angle of the output light beam.

[0059] With reference to Figure 1 and Figure 2 , the output fiber 1 can adopt a multi-clad multi-channel fiber, the point ring light beam is transmitted from the output fiber 1 to the graded-index fiber 2, the output fiber 1 includes a core 5 and a first cladding 6, a second cladding 7 and an outer cladding which successively coat the core 5, the outer cladding includes a first tapered structure V1, the first tapered structure V1 is used to control the size of the divergence angle of the output light beam of the output fiber 1. Taking the output fiber 1 with 4 clad layers as an example, the output fiber 1 includes a core 5 and a first cladding 6, a second cladding 7, a third cladding 8, a fourth cladding 9 and a coating layer 10 which successively coat the core 5, at least part of the fourth cladding 9 close to the graded-index fiber 2 includes the first tapered structure V1. That is, the fourth cladding 9 of the output fiber 1 is tapered, after processing, the first cladding 6, the second cladding 7 and the third cladding 8 remain unchanged, the fourth cladding 9 presents the first tapered structure V1, the diameter of the fourth cladding 9 changes in a tapered manner and gradually decreases along the light path direction.

[0060] Figure 3 Another structure diagram of the output fiber provided by the present application is provided, with reference to Figure 3 , the output fiber 1 includes a core 5 and a first cladding 6, a second cladding 7, a third cladding 8 and a coating layer 10 which successively coat the core 5. The output fiber 1 includes 3 clad layers, at least part of the third cladding 8 close to the graded-index fiber 2 includes the first tapered structure V1, that is, the third cladding 8 of the output fiber 1 is tapered, after processing, the first cladding 6 and the second cladding 7 remain unchanged, the third cladding 8 presents the first tapered structure V1, the diameter of the third cladding 8 changes in a tapered manner and gradually decreases along the light path direction.

[0061] It should be noted that in some embodiments, the output fiber 1 includes the core 5 and the first cladding layer 6, the second cladding layer 7 and the coating layer 10 successively covering the core 5. The second cladding layer 7 arranged close to at least a partial region of the graded-index fiber 2 includes a first tapered structure V1, that is, the second cladding layer 7 of the output fiber 1 is tapered, and the first cladding layer 6 remains unchanged after the processing, the second cladding layer 7 has the first tapered structure V1, and the diameter of the second cladding layer 7 changes in a tapered manner and gradually decreases along the light path direction.

[0062] With reference to Figure 4 continuously, the core 5 of the output fiber 1 transmits the inner ring light beam, and the core wavelength is , the cladding layer of the output fiber 1 transmits the outer ring light beam, and the cladding layer wavelength is , wherein , or . The actual light beam transmission needs to be reasonably set, and the embodiments of the present application are not limited. Wherein, the inner ring light beam refers to the light beam transmitted in the fiber core, and the outer ring light beam refers to the light beam transmitted in the fiber cladding.

[0063] In the embodiments of the present application, by tapering the outer cladding layer of the output fiber 1, the light beams in the multi-cladding multi-channel fiber can be modulated, the divergence angle of the outer ring light beam can be adjusted, and the light beam quality can be improved.

[0064] Wherein, the tapering processing provided by the present application can be realized by processes such as fusion drawing, laser writing, grinding and polishing, and the embodiments of the present application are not limited.

[0065] In some embodiments, as shown in Figure 5 , the output fiber 1 includes the core 5 and the first cladding layer 6 and the coating layer 10 successively covering the core 5. In this embodiment, the output fiber transmits and outputs the point ring light beam through the output fiber core.

[0066] In some embodiments, as shown in Figure 6 , the graded-index fiber 2 includes a graded-index core 21 and an outer cladding layer 22, and the input end of the graded-index fiber 2 close to at least a partial region of the output fiber 1 includes a second tapered structure V2, and / or the output end of the graded-index fiber 1 close to at least a partial region of the output head 3 includes a third tapered structure V3.

[0067] For example, the outer cladding layer 22 of the input end and the output end of the graded-index fiber 2 is tapered to be the second tapered structure V2 and the third tapered structure V3 respectively. As shown in Figure 1 , the core diameter D1 of the graded-index core 21 can be greater than the diameter D4 of the fourth cladding layer 9 (outer cladding layer) of the output fiber 1 after tapering, that is, D1>D4, which is conducive to collecting and carrying more incident light of a larger solid angle range.

[0068] wherein, the reference Figure 6 As shown in the figure, the included angle of the second taper structure V2 and the third taper structure V3 of the outer cladding 22 of the input end and the output end of the graded-index fiber 2 after taper processing is , and the included angle of the fourth cladding of the output end of the output fiber 1 after taper processing is , and The size of α and β can be reasonably adjusted according to actual needs, which is not limited here, and exemplarily, α = β, or The included angle of the second taper structure V2 and the third taper structure V3 can be the same or different, which is not limited in the embodiments of the present application. When there is a slight specification difference in the fiber, the included angle of the second taper structure V2 and the third taper structure V3 can be adjusted to offset the error, so as to realize the consistency convergence of the beam control performance of batch products, and significantly improve the collimation accuracy and coupling accuracy of the fiber to the light beam. The fault tolerance and product accuracy of the production process are improved.

[0069] In the embodiments of the present application, the outer cladding of the input end and the output end of the graded-index fiber is tapered, and the tapered input end is fused with the output end of the output fiber. After taper processing of the graded-index fiber, the receiving angle of the optical waveguide can be increased at the input end of the graded-index fiber, so that more incident angle laser can be transmitted in the optical waveguide, thereby improving the light collecting capacity of the optical waveguide, shaping the light beam, and reducing the loss during fusion of the output fiber 1 through mode field matching. The output end of the graded-index fiber can further compress the output beam divergence angle. At the same time, the mode matching with the target fiber can be realized by combining the smooth transition of the mode field diameter, the continuous connection of the refractive index distribution and the mode filtering, and the coupling loss in the fusion process is significantly reduced.

[0070] In some embodiments, the outer cladding of the graded-index fiber can also be tapered, so that the diameter of the outer cladding of the graded-index fiber gradually increases from the input end to the output end. The taper structure reduces the constraint ability of the outer cladding of the output end to the light field in the core, weakens the inherent self-focusing effect of the graded-index fiber, and significantly reduces the suppression effect of the fiber on the inner and outer ring light beam divergence. The output inner and outer ring light beams are more likely to naturally diffuse, so that the divergence angle of the output inner and outer ring light beams increases, and the inner and outer ring light beam expansion effect is realized.

[0071] In some embodiments, the length of the graded-index fiber 2 ranges from:

[0072] L = n x P; n > 0, n is an integer.

[0073] Where L is the length; P is the period, which refers to the length of the optical fiber that the beam travels to complete one full oscillation cycle as it propagates along a sinusoidal trajectory within the fiber; and n is the number of full oscillation cycles completed within the graded-index fiber. The period P can also be called the pitch, and the units for the lengths of L and P are mm.

[0074] The pitch of graded-index fiber 2 is mainly determined by the refractive index distribution of the fiber core, and its calculation formula is as follows; Where P is the pitch and a is the core radius. The pitch is the relative refractive index difference. The pitch formula does not include a wavelength parameter; therefore, theoretical derivation shows that wavelength changes do not directly alter the pitch value. Thus, it can be concluded that for inner and outer ring beams of the same or different wavelengths transmitted through graded-index fiber 2, the graded-index fiber 2 has the same effect on adjusting the divergence angle.

[0075] like Figure 7 As shown in (b) of the diagram, the graded-index fiber 2 includes a graded-index core 21 and an outer cladding layer 22 and a second coating layer 23 sequentially covering the graded-index core 21. Figure 7 As shown in Figure (a), the refractive index of the gradient fiber core 21 is n1, and the refractive index of the outer cladding 22 is n2, where n2 > n1. From the center to the edge of the gradient fiber core 21, the refractive index n1 gradually decreases to n2.

[0076] Combination Figure 7 As shown in Figure (c), diverging beam a is the outer ring beam transmitted in the cladding of output fiber 1, and diverging beams b and c are the inner ring beams transmitted in the core of output fiber 1. In this application, the core diameter of graded-index fiber 2 is set to be larger than the diameter of the outer cladding of output fiber 1 after tapering, so that beams with different incident angles can be coupled into the graded core 21 of graded-index fiber 2 for transmission. For example, diverging beams a, b, and c are all incident from one end (input end face) of the graded core 21 of integer-period graded-index fiber 2. The beams are deflected along a sinusoidal trajectory in the graded core 21 of graded-index fiber 2. The "divergence tendency" at the time of incident is gradually canceled out by the continuous refraction of the graded refractive index. When the beams are transmitted to the other end of graded-index fiber 2, the divergence angle of the beams converges significantly. The graded-index fiber 2 has the same effect on adjusting the divergence angle of the inner and outer ring beams of the same or different wavelengths.

[0077] Specifically, the inner ring light beam (divergent light beam b, c) is incident near the fiber center axis o' of the graded-index fiber 2, in the region with the highest refractive index n1 of the graded fiber core 21, and the axial part of the graded-index fiber 2 is similar to a weak converging lens. During transmission, the light beam is subjected to a weak converging effect radially inward because the axial refractive index is higher than the peripheral refractive index, and the light beam trajectory is approximately a sinusoidal curve. When the light beam is close to the output end, the radial angle of the light beam changes slightly, the divergence angle of the inner ring light beam is reduced to a certain extent, and the light beam converges towards the central optical axis.

[0078] The outer ring light beam (divergent light beam a) is incident from the edge of the fiber, and is initially located in a region with a high refractive index. As it propagates outward, the peripheral refractive index n1 of the graded fiber core 21 gradually decreases, and the light beam is subjected to a stronger radial refractive index gradient force. Compared to the incident state, the angle distribution of the outer ring light beam becomes relatively concentrated, and the divergence angle decreases significantly. In this way, the output light divergence angle is adjusted to achieve a smaller divergence angle output.

[0079] In the embodiments of the present application, the length of the graded-index fiber is set to satisfy L = n x P; n > 0, n is an integer. The light beam is incident from the input end face of the graded fiber core of the integer period graded-index fiber, and the light beam deflects along a sinusoidal trajectory in the graded fiber core of the graded-index fiber. The "divergence trend" at the time of incidence is gradually offset by the continuous refraction of the graded-index fiber. When the light beam is transmitted to the output end of the graded-index fiber, the divergence angle of the light beam converges significantly, thereby achieving the effect of suppressing the divergence trend of the inner and outer ring light beams and reducing the divergence angle of the inner and outer ring light beams.

[0080] In some embodiments, the length of the graded-index fiber 2 is preferably in the range of:

[0081] L = (n + 1 / 4) x P; n ≥ 0, n is an integer.

[0082] Wherein, L is the length; P is the period, which refers to the length of the fiber that the light beam travels along a sinusoidal trajectory in the fiber to complete one complete oscillation cycle; n is the number of complete oscillation cycles in the graded-index fiber. The period P can also be referred to as the pitch, and the lengths of L and P are in mm.

[0083] For example, as shown in (a) of FIG. 1, Figure 8 The graded-index fiber 2 includes a graded fiber core 21, an outer cladding 22, and a second coating layer 23 that successively covers the graded fiber core 21, as shown in (a) of FIG. 1. Figure 8 As shown in (b) of FIG. 1, the refractive index of the graded fiber core 21 is n1, the refractive index of the outer cladding 22 is n2, and n2 > n1. From the center to the edge of the graded fiber core 21, the refractive index n1 gradually decreases to n2.

[0084] Combination Figure 8 As shown in (a) of the accompanying drawings, the divergent light beam a is the outer ring light beam transmitted in the cladding of the output fiber 1, and the divergent light beams b and c are the inner ring light beams transmitted in the core of the output fiber 1. The core diameter of the graded-index fiber 2 is greater than the diameter of the outer cladding of the output fiber 1 after the taper processing, so that the light beams with different incident angles can be coupled into the graded core 21 of the graded-index fiber 2 for transmission. For example, the divergent light beams a, b and c are incident from one end (input end face) of the graded core 21 of the 1 / 4 period graded-index fiber 2, and the light beams are deflected along a sinusoidal trajectory in the graded core 21 of the graded-index fiber 2. The “divergence trend” at the time of incidence is gradually offset by the continuous refraction of the graded-index, and when transmitted to the other end (output end face) of the graded-index fiber 2, the outgoing inner ring light beam tends to be parallel light, and the outgoing outer ring light converges towards the central optical axis. The graded-index fiber 2 has the same adjustment effect on the divergence angles of the inner and outer ring light beams of the same or different wavelengths.

[0085] Specifically, the inner ring light beams (divergent light beams b and c) are incident near the fiber central axis o’ of the graded-index fiber 2, and are located in the region with the highest refractive index n1 of the graded core 21. The axial part of the 1 / 4 period graded-index fiber 2 is similar to a weak converging lens. When the light beam is transmitted, the axial refractive index is higher than the peripheral refractive index, and the light beam is subjected to a weak converging action radially inward, and the light beam trajectory is approximately a sinusoidal curve. When the light beam is close to the output end, the radial angle of the light beam changes slightly, and the parallelism is high when output. The divergence angle of the inner ring light beam is reduced to a certain extent.

[0086] The outer ring light beam (divergent light beam a) is incident from the edge of the fiber, and is located in the region with the highest refractive index at the initial stage of transmission. Then, as the light beam propagates outward, the peripheral refractive index n1 of the graded core 21 gradually decreases, and the light beam is subjected to a stronger radial refractive index gradient force. The direction of the outer ring light beam is adjusted by a large margin, and the angle distribution of the outer ring light beam becomes relatively concentrated compared with that at the time of incidence. The divergence trend is obviously inhibited, and the outer ring light beam changes from outward divergence to convergence towards the central optical axis, and the divergence angle decreases obviously. In this way, the adjustment of the output light divergence angle is realized, and a smaller divergence angle output is realized.

[0087] In this embodiment, the length of the graded-index fiber is set such that it satisfies L = (n + 1 / 4) × P, where n ≥ 0 and n is an integer. The light beam is incident from the input end face of the graded core of the 1 / 4-period graded-index fiber. The beam deflects along a sinusoidal trajectory within the graded core, and the initial divergence tendency is gradually canceled out by the continuous refraction of the graded-index fiber. When transmitted to the output end of the graded-index fiber, the outgoing inner ring beam approaches parallel light, and the outgoing outer ring beam converges towards the central optical axis. The divergence angle of the beam is significantly reduced, thereby suppressing the divergence tendency of the inner and outer ring beams and reducing their divergence angles.

[0088] In some embodiments, such as Figure 9 As shown in Figure (b), the graded-index fiber 2 includes a graded-index core 21 and an outer cladding layer 22 and a second coating layer 23 sequentially covering the graded-index core 21. Figure 9 As shown in Figure (a), the refractive index of the graded-index fiber core 21 is n1, and the refractive index of the outer cladding 22 is n2. From the center to the edge of the graded-index fiber core 21, the refractive index n1 gradually increases, and the refractive index of the graded-index fiber core is greater than that of the outer cladding 22. The length range of the graded-index fiber 2 is:

[0089] L = (n + 1 / 4) × P; n ≥ 0, where n is an integer.

[0090] Where L is the length; P is the period, which refers to the length of the optical fiber that the beam travels to complete one full oscillation cycle as it propagates along a sinusoidal trajectory within the fiber; and n is the number of full oscillation cycles completed within the graded-index fiber. The period P can also be called the pitch, and the units for the lengths of L and P are mm.

[0091] Combination Figure 9 As shown in Figure (c), diverging beam a is the outer ring beam transmitted in the cladding of output fiber 1, and diverging beams b and c are the inner ring beams transmitted in the core of output fiber 1. In this application, the core diameter of graded-index fiber 2 is set to be larger than the diameter of the outer cladding of output fiber 1 after tapering, so that beams with different incident angles can be coupled into the graded core 21 of graded-index fiber 2 for transmission. For example, diverging beams a, b, and c are all incident from one end (input end face) of the graded core 21 of graded-index fiber 2. The beams are deflected towards the region (edge) with high refractive index inside the graded core 21 of graded-index fiber 2. When they are transmitted to the other end (output end face) of graded-index fiber 2, the emitted inner and outer ring beams both show an outward divergence trend, and the divergence angle of the inner and outer ring beams is expanded.

[0092] In the embodiment, by selecting the graded-index fiber with gradually increasing refractive index from the center to the edge, the inner and outer ring light beams are biased to the edge of the fiber core with large refractive index during the transmission of the graded-index fiber, and the overall light beam presents a trend of outward divergence. Finally, the divergence angles of the inner and outer ring light beams are both expanded when the light beam is emitted from the output end. By such arrangement, the optical device can adjust the divergence angles of the inner and outer ring light beams to achieve the effect of expanding the divergence angle of the output light beam.

[0093] The quartz output head can be selected according to actual application requirements. The output end face shape of the output head 3 can be a plane, a spherical surface or an arc surface, and the embodiment of the application is not limited.

[0094] In the embodiment, the output end of the graded-index fiber and the input end of the output head are fused by the fiber and end cap fusion technology. The output end of the tapered output fiber is fused with the input end of the graded-index fiber, the output end of the graded-index fiber 2 is fused with the input end of the quartz output head, and the fused device is installed in the external supporting external shell to form an optical device for adjusting the divergence angle of the output light of the laser through the graded-index fiber, which realizes the precise regulation and control of the divergence angle of the output light of different wavelengths or the same wavelength.

[0095] In summary, the application adopts a multi-clad multi-channel fiber for tapering preprocessing, which can realize the pre-compression of the divergence angle of the outer ring light beam. The graded-index fiber can modulate the inner and outer ring light beams respectively, so that the divergence angles of the inner and outer ring light beams are reduced, and the output parallelism is improved. At the same time, the gradual change characteristic of the graded-index fiber makes the optical path of light beams with different incident angles or wavelengths consistent, avoiding the uneven divergence angle caused by the optical path difference, and further ensuring the stability of the divergence angle regulation. The quartz output head can be selected in different shapes and sizes according to the needs, so as to realize the "secondary shaping" of the light beam output by the graded-index fiber. By tapering the multi-clad multi-channel fiber and the graded-index fiber respectively, the smooth transition of the optical mode field is realized, the coupling loss is significantly reduced, and the optical transmission efficiency is improved.

[0096] Compared with the prior art, the present application has the advantages of simple structure, no need for additional optical elements, higher stability, simple process, standardization, suitable for mass production, and greatly reduced manufacturing cost per unit.

[0097] At the same time, the technical scheme of the application is not limited to a single wavelength, but also has the flexibility of "multi-wavelength compatibility", which meets the requirements of various laser transmission.

[0098] Based on the same inventive concept, the application further provides a preparation method of the optical fiber device, Figure 12 A flowchart of the preparation method of the optical fiber device provided by the application is shown in Figures 1-8 The preparation method comprises the following steps:

[0099] S101, providing an output optical fiber, the output optical fiber comprising a core and a cladding, for outputting a point-ring light beam.

[0100] S102, providing a graded-index optical fiber, the graded-index optical fiber being used for adjusting the optical path of the point-ring light beam to achieve adjustment of the divergence angles of the inner and outer ring light beams.

[0101] S103, providing an output head, the output head being used for outputting the adjusted light beam.

[0102] S104, connecting the output end of the output optical fiber with the input end of the graded-index optical fiber, and connecting the output end of the graded-index optical fiber with the input end of the output head.

[0103] In some embodiments, the output optical fiber 1 is a multi-clad multi-channel optical fiber.

[0104] Referring to Figure 2 , first, at least one outer cladding in the output end of the output optical fiber 1 is tapered, so that the output end is a tapered structure, and the output end is scanned and cut to a desired diameter. Specifically, a certain length of the coating layer 10 of the output optical fiber 1 is stripped, at least a portion of the fourth cladding 9 close to the graded-index optical fiber 2 is tapered, the core 5, the first cladding 6, the second cladding 7, the third cladding 8 remain unchanged after processing, and the fourth cladding 9 is in a first tapered structure V1. The multi-clad multi-channel tapered optical fiber of different wavelengths (or the same wavelength) is obtained by performing diameter scanning on the tapered multi-clad multi-channel optical fiber and cutting at the desired diameter.

[0105] In some embodiments, the output optical fiber 1 is composed of the core 5 and the first cladding 6 covering the core 5.

[0106] Referring to Figure 5 , first, at least one outer cladding in the output end of the output optical fiber 1 is tapered, so that the output end is a tapered structure, and the output end is scanned and cut to a desired diameter. Specifically, a certain length of the coating layer 10 of the output optical fiber 1 is stripped, at least a portion of the fourth cladding 9 close to the graded-index optical fiber 2 is tapered, the core 5, the first cladding 6, the second cladding 7, the third cladding 8 remain unchanged after processing, and the fourth cladding 9 is in a first tapered structure V1. The multi-clad multi-channel tapered optical fiber of different wavelengths (or the same wavelength) is obtained by performing diameter scanning on the tapered multi-clad multi-channel optical fiber and cutting at the desired diameter.

[0107] It is understood that the output optical fiber 1 only includes the first cladding 6, and in this embodiment, the outer cladding is the first cladding 6.

[0108] refer to Figure 6 At least one cladding layer at the input and output ends of the graded refractive index fiber 2 is tapered to make both ends tapered structures, and the input and output ends are scanned and cut to the expected diameter.

[0109] Specifically, a certain length of the second coating layer 23 of the graded-index fiber 2 is stripped. At least a portion of the outer cladding layer 22 near the input end of the graded-index fiber 2, close to the output fiber 1, is tapered to obtain a second tapered structure V2. At least a portion of the outer cladding layer 22 near the output head 3 of the graded-index fiber 2 is tapered to obtain a third tapered structure V3. The graded-index core 21 remains unchanged after the treatment, and the two ends of the outer cladding layer 22 form the second tapered structure V2 and the third tapered structure V3. The input and output ends of the graded-index fiber 2 are then scanned for diameter, and cut at the desired diameter D to obtain a usable graded-index fiber 2.

[0110] Finally, using fiber optic fusion splicing technology, the output end of the tapered output fiber 1 is fused to the input end of the graded-index fiber 2, the output end of the graded-index fiber 2 is fused to the output head 3, and the fused components are installed inside the external housing. This results in an optical device that uses graded-index fiber to achieve adjustable divergence angles for output light of different wavelengths.

[0111] In summary, this embodiment of the application, by tapering multi-clad multi-channel optical fibers and graded-index optical fibers, and fusing them with a quartz output head, modulates the beam through the graded-index fiber. As the beam propagates within the graded-index fiber, it is continuously adjusted to ensure that beams at different incident angles have approximately the same optical path. This allows the beams to reach the tapered output end of the graded-index fiber almost simultaneously, thereby adjusting the output light divergence angle. The beam is then output through the quartz output head, thus achieving control over the divergence angle of output light of different wavelengths or the same wavelength. This optical device does not require special optical components and has the advantages of simple manufacturing process and low cost.

[0112] The following is a specific embodiment to illustrate the fiber optic device with adjustable output light divergence angle provided in this application.

[0113] Example

[0114] Combination Figures 1-8 As shown in the figure, this application provides an optical fiber device that achieves adjustable output light divergence angle through graded refractive index optical fiber 2.

[0115] The optical device comprises a multi-clad multi-channel optical fiber, which is composed of an output optical fiber 1, a graded-index optical fiber 2 and an output head 3. The size of the multi-clad multi-channel optical fiber is 34 / 48 / 102 / 120 / 360 / 650, that is, the diameter of the core 5 is 34 μm, the diameter of the first cladding layer 6 is 48 μm, the diameter of the second cladding layer 7 is 102 μm, the diameter of the third cladding layer 8 is 120 μm, the diameter of the fourth cladding layer 9 is 360 μm, and the diameter of the coating layer 10 is 650 μm. The fourth cladding layer 8 of the output end of the multi-clad multi-channel optical fiber is tapered to form a first tapered structure V1.

[0116] The size of the graded-index optical fiber 2 is 200 / 220, that is, the diameter of the graded core 21 is 200 μm, and the diameter of the outer cladding layer 22 is 220 μm. The outer cladding layer 22 of the input end and the output end of the graded-index optical fiber 2 is tapered, and the two ends form a second tapered structure V2 and a third tapered structure V3. Among them, 200 / 220 is the conventional size of the graded-index optical fiber 2, the core diameter D1 of the graded core 21 of the graded-index optical fiber 2 is greater than the diameter D4 of the fourth cladding layer 9 (outer cladding layer) of the output optical fiber 1, and thus designed, which can collect and carry the incident light of a larger solid angle range output from the output optical fiber 1. The output head 3 adopts a quartz output head, and the size is .

[0117] The first tapered structure V1 of the output optical fiber 1 and the second tapered structure V2 of the graded-index optical fiber 2 are fused by optical fusion technology, and then the third tapered structure V3 of the graded-index optical fiber 2 and the input end of the quartz output head are fused by end cap fusion technology, and the fused device is installed in the external shell 4 to obtain an optical device with adjustable output light divergence angle through the graded-index optical fiber.

[0118] Figure 10 is a schematic diagram of the light spot at the beam waist of the output beam of the optical fiber device provided by the present application, and Figure 10 The difference between the divergence angles of the inner and outer ring beams in the prior art leads to uneven light intensity distribution of the beam, and the propagation path and focusing characteristics of the inner and outer ring beams are quite different, which cannot output a point ring light spot with uniform and clear boundaries, and it is difficult to accurately control the light spot shape. In laser processing applications, uneven distribution of light intensity energy density will also lead to uneven local heating of the processed surface material, thereby causing poor processing quality and precision.

[0119] Figure 11 is a schematic diagram of the light spot at the beam waist of the output beam of the optical fiber device provided by the present application, and Figure 11As shown, by using the graded-index fiber, the present application effectively reduces the divergence angles of the inner and outer ring light beams, so that the maximum angular ranges of the inner and outer ring light beams during propagation are similar, the propagation paths and focusing characteristics of the inner and outer ring light beams are similar, the convergence of the inner and outer ring light beams is more regular and symmetrical, a clear and explicit ring boundary can be formed, the size and shape of the focused light spot are more regular, the light spot has high precision and uniform light intensity distribution, the local power density caused by light field concentration is reduced, thereby reducing the light loss caused by nonlinear effects, and the mode interference between light beams with different numerical apertures can be reduced, so that the light spot is more stable. In laser processing, the focused light spot with high energy concentration can more effectively cut, weld or punch the material, thereby improving the processing efficiency, precision and quality.

[0120] To sum up, the optical device with adjustable output light divergence angle provided by the embodiments of the present application adopts a multi-clad multi-channel fiber for taper structure processing, the fiber core and the plurality of inner cladding of the processed multi-clad multi-channel fiber remain unchanged, and the outer light transmission channel cladding is in a taper structure. The two ends of the graded-index fiber are tapered, the fiber core of the processed graded-index fiber remains unchanged, the pre-modulation of each waveguide layer in the multi-clad multi-channel fiber is realized, and the modulation by the graded-index fiber is performed, so that the light beams with different incident angles have approximately the same optical path when the light beams are transmitted in the graded-index fiber, thereby enabling the light beams to almost simultaneously reach the output quartz head, so as to simultaneously control the output divergence angle, and then the output light divergence angle is controlled by the output quartz head, thereby realizing the precise controllability of the output light divergence angle and adapting to multiple scene requirements. The optical device has the advantages of simple optical structure, simple manufacturing process and strong stability, and meets the transmission requirements of high-power fiber lasers.

[0121] Based on the same inventive concept, the embodiments of the present application also provide a laser, which includes the fiber device provided by the above embodiments. Exemplarily, the embodiments of the present application are not limited to, for example, 915 nm, 940 nm, 976 nm, 1 μm, 1.5 μm wavelength fiber lasers and the like. The laser transmits laser light through the four-clad fiber structure provided by the above embodiments, and can be applied to material cutting, welding, punching and the like.

[0122] Based on the same inventive concept, the embodiments of the present application also provide a laser processing device, which includes the laser provided by the above embodiments, and can further include an auxiliary gas system, a control system and software, a safety protection system, a detection and feedback system, an automatic feeding and discharging system, a mechanical hand or a conveyor belt, a workpiece clamp, a dust removal system and the like. The laser processing device also has the effective effects of the light spot conversion system provided by the above embodiments, which will not be described herein.

[0123] Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that features of various embodiments of the present application can be partially or wholly coupled or combined with each other, and can be cooperated with each other and technically driven in various ways. Various obvious changes, re-adjustments, mutual combinations and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments only, but can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims attached.

Claims

1. An optical fiber device, characterized in that, Including those connected sequentially: Output fiber, including core and cladding, is used to output a point-loop beam; Graded-index fiber is used to adjust the optical path of the dot ring beam to adjust the divergence angle of the inner and outer ring beams. Output head, used to output the adjusted beam.

2. The optical fiber device according to claim 1, characterized in that, The length range of the graded refractive index optical fiber satisfies: L = (n + 1 / 4) × P; n ≥ 0, where n is an integer; Where L is the length; P is the period, which refers to the length of the optical fiber that the beam travels to complete one full oscillation cycle as it propagates along a sinusoidal trajectory within the optical fiber; n is the number of full oscillation cycles completed within the graded-index optical fiber; the units of length for L and P are mm.

3. The optical fiber device according to claim 1, characterized in that, The output optical fiber includes a core and a first cladding; the first cladding includes a first tapered structure, which is used to control the size of the divergence angle of the output beam from the output optical fiber. Alternatively, the output optical fiber includes a core, a first cladding, and a second cladding; the second cladding includes a first tapered structure, which is used to control the size of the divergence angle of the output beam from the output optical fiber. Alternatively, the output optical fiber includes a core, a first cladding, a second cladding, and an outer cladding; the outer cladding includes a first tapered structure, which is used to control the size of the divergence angle of the output beam from the output optical fiber.

4. The optical fiber device according to claim 3, characterized in that, The outer cladding includes a third cladding and a coating layer, wherein the third cladding near at least a portion of the graded-index fiber includes the first tapered structure; or, the outer cladding includes a third cladding, a fourth cladding, and a coating layer, wherein the fourth cladding near at least a portion of the graded-index fiber includes the first tapered structure.

5. The optical fiber device according to claim 1, characterized in that, The graded-index fiber includes a graded-index core and an outer cladding. At least a portion of the input end of the graded-index fiber near the output fiber includes a second tapered structure, and / or, at least a portion of the output end of the graded-index fiber near the output head includes a third tapered structure.

6. The optical fiber device according to claim 3, characterized in that, The core diameter of the graded-index optical fiber is larger than the diameter of the cladding of the output optical fiber after tapering.

7. A method for fabricating an optical fiber device, used to fabricate the optical fiber device according to any one of claims 1-6, characterized in that, include: Provide an output optical fiber, the output optical fiber comprising a core and a cladding, for outputting a dot-loop beam; A graded-index optical fiber is provided, which is used to adjust the optical path of the dot ring beam to adjust the divergence angle of the inner and outer ring beams; An output head is provided for outputting the adjusted beam; Connect the output end of the output optical fiber to the input end of the graded refractive index optical fiber, and connect the output end of the graded refractive index optical fiber to the input end of the output head.

8. The preparation method according to claim 7, characterized in that, The fabrication steps of the output optical fiber include: The outer cladding of the output fiber is tapered to make the output end a tapered structure, and the output end is scanned and cut to the expected diameter; The fabrication steps of the graded-index optical fiber include: The outer cladding at the input and output ends of the graded refractive index fiber is tapered to form tapered structures at both ends, and the input and output ends are scanned and cut to the expected diameter. The connection steps for each component include: The output end of the tapered output fiber is fused to the input end of the graded refractive index fiber, and the output end of the graded refractive index fiber is fused to the input end of the output head. The welded components are installed inside the outer housing.

9. A laser, characterized in that, Includes the optical fiber device as described in any one of claims 1-6.

10. A laser processing device, characterized in that, Includes the laser as described in claim 9.

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