Fiber and laser processing equipment

Abstract

This invention provides a fiber that emits laser light with a desired numerical aperture using a relatively simple configuration. [Solution] The fiber 10 has a core 11 and a cladding 12 provided on the outer periphery of the core 11. The incident region is defined as a region of a predetermined length extending longitudinally from the incident end of the core 11. The refractive index distribution of the core 11 in the incident region is different from the refractive index distribution of the core 11 in at least one of the longitudinal and radial directions of the core 11 compared to the refractive index distribution of the core 11 in the region excluding the incident region.

Description

Technical Field

[0001] The present invention relates to a fiber and a laser processing apparatus.

Background Art

[0002] Patent Document 1 discloses a laser processing machine provided with an adjustment mechanism on the incident side of a fiber. The adjustment mechanism adjusts the divergence angle of the incident laser light to the fiber, that is, the numerical aperture of the incident laser light, so that the divergence angle of the laser light emitted from the fiber, that is, the numerical aperture of the emitted laser light, is always constant.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the conventional invention, in order to obtain the desired numerical aperture of the laser light emitted from the fiber, it is necessary to separately provide an adjustment mechanism for adjusting the numerical aperture of the incident laser light to the fiber, and there is a problem that the component cost increases.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a fiber that emits laser light having a desired numerical aperture with a relatively simple configuration.

Means for Solving the Problems

[0006] The first invention is a fiber having a core made of quartz and a cladding provided on the outer periphery of the core, which transmits laser light incident from the incident end of the core and exits from the exit end of the core, wherein the incident region is a region of a predetermined length extending longitudinally from the incident end of the core, and the refractive index distribution of the core in the incident region is different in at least one of the longitudinal and radial directions of the core compared to the refractive index distribution of the core in the region excluding the incident region.

[0007] In the first invention, a fiber that emits laser light with a desired numerical aperture can be provided by making the refractive index distribution of the core in the incident region different from the refractive index distribution of the region excluding the incident region in at least one of the longitudinal and radial directions of the core.

[0008] The second invention is a fiber of the first invention in which the refractive index of the core in the incident region is higher than the refractive index of the core in the region excluding the incident region.

[0009] In the second invention, the refractive index distribution of the core in the incident region can be changed by increasing the refractive index of the core in the incident region.

[0010] The third invention is a fiber of the first or second invention in which the refractive index distribution of the core in the incident region is non-uniform in at least one of the longitudinal and radial directions of the core.

[0011] In the third invention, scattering due to refractive index non-uniformity makes it possible to make the numerical aperture of the emitted laser light greater than the numerical aperture of the incident laser light.

[0012] The fourth invention is a fiber of the first or second invention, wherein the refractive index distribution of the core in the incident region is formed by processing laser light irradiated onto the incident region.

[0013] In the fourth invention, the refractive index of the core can be locally changed by altering the core in the incident region with processing laser light.

[0014] The fifth invention is that, in the fiber of the fourth invention, the output of the laser light for processing and the output of the laser light transmitted from the input end to the output end of the core are the same.

[0015] In the fifth invention, the laser light for processing and the laser light for transmitting through the core can be emitted using the same laser oscillator.

[0016] The sixth invention is the fiber of the fourth invention, wherein the wavelength of the laser light for processing is 400 nm or more and less than 500 nm.

[0017] In the sixth invention, laser light of an appropriate wavelength can be used depending on the core material.

[0018] The seventh invention is the fiber of the third invention, wherein the refractive index distribution of the core in the incident region is non-uniform in the longitudinal direction of the core.

[0019] In the seventh invention, by making the refractive index distribution of the core in the incident region non-uniform in the longitudinal direction of the core, the numerical aperture of the emitted laser light can be made larger than the numerical aperture of the incident laser light due to scattering caused by the non-uniformity of the refractive index.

[0020] The eighth invention is a laser processing apparatus comprising a fiber according to the first or second invention and a laser oscillator that emits the laser light incident on the fiber.

[0021] The eighth invention provides a laser processing apparatus comprising a fiber and a laser oscillator. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a fiber that emits laser light with a desired numerical aperture.

Brief Description of the Drawings

[0023] [Figure 1] It is a schematic configuration diagram of the laser processing apparatus according to Embodiment 1. [Figure 2] It is a side cross-sectional view showing the configuration of the fiber. [Figure 3] It is a side cross-sectional view showing the configuration of the fiber before the homogenization process. [Figure 4] It is a side cross-sectional view showing the configuration of the fiber during the homogenization process. [Figure 5] It is a side cross-sectional view showing the configuration of the fiber after the homogenization process. [Figure 6] It is a diagram showing the radial refractive index distribution in the cross-section taken along the C-C arrow, D-D arrow, and E-E arrow of FIG. 5. [Figure 7] It is a diagram showing the radial refractive index distribution in the cross-section taken along the A-A arrow of FIG. 5. [Figure 8] It is a diagram showing the radial refractive index distribution in the cross-section taken along the B-B arrow of FIG. 5. [Figure 9] It is a graph showing the relationship between the irradiation time of the incident laser light and the aperture number of the emitted laser light. [Figure 10] It is a flowchart showing the procedure of the homogenization process. [Figure 11] It is a side cross-sectional view showing the configuration of the fiber according to Embodiment 2. [Figure 12] It is a side cross-sectional view showing the configuration of the first divided fiber before the homogenization process. [Figure 13] It is a side cross-sectional view showing the configuration of the first divided fiber after the homogenization process. [Figure 14] It is a side cross-sectional view showing the state of fusion connection between the first divided fiber and the second divided fiber after the homogenization process. [Figure 15] It is a graph showing the relationship between the irradiation time of the incident laser light and the aperture number of the emitted laser light. [Figure 16] It is a flowchart showing the procedure of the homogenization process. [Figure 17]This is a side cross-sectional view showing the fiber configuration according to this third embodiment. [Figure 18] This is a side cross-sectional view showing the state after irradiating the first divided fiber with drawing laser light before the heterogeneity treatment. [Figure 19] This is a side cross-sectional view showing the structure of the first divided fiber after heterogeneity treatment. [Figure 20] This is a side cross-sectional view showing the state of fusion splicing the first divided fiber and the second divided fiber after heterogeneity treatment. [Figure 21] This is a side cross-sectional view showing the fiber structure after heterogeneity treatment. [Figure 22] This figure shows the refractive index distribution in the radial direction in the cross-section viewed from the arrow GG in Figure 21. [Figure 23] This figure shows the radial refractive index distribution in the cross-section viewed from the FF arrow in Figure 21. [Figure 24] This graph shows the relationship between the number of times the laser beam is irradiated during drawing and the numerical aperture of the emitted laser beam. [Figure 25] This is a flowchart illustrating the procedure for heterogeneity treatment. [Modes for carrying out the invention]

[0024] The embodiments will be described in detail below, with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.

[0025] The attached drawings and the following description are provided to enable a person skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0026] Embodiment 1 As shown in Figure 1, the laser processing apparatus 1 comprises a laser oscillator 2, a laser head 3, a robot 4, a control unit 5, and a fiber 10.

[0027] The laser oscillator 2 is connected to the input end of the fiber 10. The laser head 3 is connected to the output end of the fiber 10. The incident laser light 20 emitted from the laser oscillator 2 is transmitted to the laser head 3 via the fiber 10, and the output laser light 30 is emitted from the laser head 3.

[0028] The laser head 3 is attached to the robot 4. The laser head 3 can change the emission position and focal position of the emitted laser beam 30 relative to the workpiece W by operating the robot 4.

[0029] The control unit 5 is connected to the laser oscillator 2, the laser head 3, and the robot 4. The control unit 5 controls the operation of the laser oscillator 2, the laser head 3, and the robot 4. In addition to the movement speed of the laser head 3, the control unit 5 controls the start and stop of the output of the emitted laser beam 30, the output intensity of the emitted laser beam 30, and so on.

[0030] As shown in Figure 2, the fiber 10 has a core 11 and a cladding 12. The fiber 10 transmits incident laser light 20 that enters from the incident end of the core 11 and emits outgoing laser light 30 from the outgoing end of the core 11.

[0031] The core 11 is formed in a circular shape. The core 11 is made of, for example, quartz. The diameter of the core 11 is, for example, φ50 μm. The core 11 is configured to have a step-index type refractive index.

[0032] Here, a step-index fiber 10 refers to a structure in which the refractive index of light has a uniform refractive index distribution within the core 11, the refractive index of the cladding 12 is lower than the refractive index of the core 11, and there is a rapidly decreasing refractive index at the interface between the core 11 and the cladding 12.

[0033] The cladding 12 is provided on the outer periphery of the core 11. The cladding 12 is made of, for example, fluorine-doped quartz. The diameter of the cladding 12 is, for example, φ400 μm. The refractive index of the cladding 12 is lower than that of the core 11.

[0034] The outer periphery of cladding 12 is covered with a second cladding of quartz (not shown). The refractive index of the second cladding is lower than that of cladding 12.

[0035] The numerical aperture (NA) of fiber 10 is determined by the refractive index of the core 11 and the refractive index of the cladding 12. For example, the numerical aperture of fiber 10 is 0.2. The longitudinal length of fiber 10 is, for example, 5 m.

[0036] In the following explanation, as shown in Figure 2, fiber 10 will be described by dividing it into three regions: the input region, the intermediate region, and the output region.

[0037] The incident laser beam 20 is incident on the incident end of fiber 10. The incident region is a region of a predetermined length that extends longitudinally from the incident end to the exit end of fiber 10. The length of the incident region is, for example, 500 mm.

[0038] Laser light 30 is emitted from the exit end of fiber 10. The emission region is a region of a predetermined length that extends longitudinally from the exit end to the input end of fiber 10. The length of the emission region is, for example, 500 mm.

[0039] The intermediate region is a region of a predetermined length that extends longitudinally between the incident region and the exit region. For example, the length of the intermediate region is 4 meters.

[0040] The refractive index distribution of the core 11 in the exit region is uniform with respect to the longitudinal and radial directions of the fiber 10. The refractive index distribution of the core 11 in the intermediate region is also uniform with respect to the longitudinal and radial directions of the fiber 10. Here, the refractive index distribution of the core 11 in the intermediate region is the same as the refractive index distribution of the core 11 in the exit region.

[0041] A modified portion 13 is provided in the core 11 in the incident region. Due to the modified portion 13, the refractive index distribution of the core 11 in the incident region is non-uniform with respect to the longitudinal and radial directions of the fiber 10. In other words, the refractive index distribution of the core 11 in the incident region is non-uniform compared to the refractive index distribution of the core 11 in the intermediate region and the exit region. The modified portion 13 will be described later.

[0042] <Fiber non-uniformity treatment> The non-uniformity treatment of fiber 10 will be described below. In this embodiment, the incident laser light 20 is a laser light for processing (machining). The non-uniformity treatment of fiber 10 is performed using the processing laser light. As shown in Figure 3, the fiber 10 before the non-uniformity treatment has a core 11 with a circular cross-section and a cladding 12 that covers the periphery of the core 11.

[0043] The diameter of core 11 is φ50 μm. The material of core 11 is quartz. The diameter of cladding 12 is φ400 μm. The refractive index of cladding 12 is lower than that of core 11.

[0044] The total length of fiber 10 is 5 m. The incident laser beam 20 is incident on the incident end of fiber 10. The incident region is a region that extends a predetermined length, for example, 500 mm, in the longitudinal direction from the incident end to the exit end of fiber 10.

[0045] Laser light 30 is emitted from the exit end of fiber 10. The emission region is a region that extends longitudinally from the exit end to the input end of fiber 10 for a predetermined length, for example, 500 mm.

[0046] The intermediate region is a region that extends longitudinally for a predetermined length, for example, 4m, between the incident region and the exit region.

[0047] In fiber 10 before heterogeneity treatment, the refractive index distribution is uniform in all regions—the incident region, the intermediate region, and the exit region—with respect to the longitudinal and radial directions of fiber 10. Furthermore, the refractive index distribution in the incident region, the intermediate region, and the exit region is identical with respect to the longitudinal and radial directions of fiber 10.

[0048] When incident laser light 20 is injected into the core 11 at the incident end of fiber 10 before the non-uniform treatment, the incident laser light 20 is confined to the core 11 and reaches the exit region via the intermediate region. Exit laser light 30 is emitted from the exit end of fiber 10.

[0049] Here, the incident laser beam 20 is, for example, a continuous wave laser beam with a multimode beam intensity distribution, wavelength 405 nm, and output power of 1 kW. The incident laser beam 20 is focused to 86.5%, with a diameter of 35 μm and a numerical aperture of 0.1 by a focusing lens (not shown), and is incident on the core 11 at the incident end of the fiber 10.

[0050] The emitted laser beam 30 is emitted from the core 11 at the exit end of the fiber 10 as laser light with the same numerical aperture of 0.1 as the incident laser beam 20. In other words, the numerical aperture of the incident laser beam 20 is equal to the numerical aperture of the emitted laser beam 30.

[0051] As shown in Figure 4, in the fiber 10 during the heterogeneity treatment, the incident laser light 20 for the treatment alters the quartz in the incident region of the core 11, creating an altered region 13.

[0052] Specifically, the refractive index of the incident region of the core 11 changes over time in accordance with the irradiation of the incident laser light 20 and the light intensity distribution of the incident laser light 20.

[0053] More specifically, interband excitation caused by the incident laser light 20 leads to a density change due to the rearrangement of Si-O bonds in the quartz core 11, resulting in a localized change in refractive index.

[0054] The distribution of altered regions 13 due to such rearrangement follows the distribution of light intensity regions, resulting in a non-uniform refractive index distribution. For example, this is disclosed in "Koichi Kajiwara, "Point Defects I in Silica Glass", NEW GLASS, Vol.33 No.124, 2018".

[0055] As the altered portion 13 is formed in the incident region of the core 11, the refractive index of the incident region of the core 11 becomes higher than the refractive index of the core 11 before the non-uniform treatment, resulting in a non-uniform refractive index distribution.

[0056] In other words, the refractive index distribution in the incident region of core 11 is different from the refractive index distribution in the intermediate region of core 11 and the refractive index distribution in the exit region of core 11.

[0057] Due to this non-uniformity of refractive index, the numerical aperture of the emitted laser light 30 from the exit end of the fiber 10 becomes greater than the numerical aperture of the incident laser light 20 (0.1) due to scattering caused by the non-uniformity of refractive index.

[0058] Then, this change in numerical aperture is monitored by measuring the output of the emitted laser beam 30 using a numerical aperture measuring device (for example, a power meter with an aperture) not shown in the diagram.

[0059] As shown in Figure 5, after the heterogeneity treatment is completed, the fiber 10 undergoes alteration of the quartz in the incident region of the core 11, and then the alteration of the quartz reaches a saturated state, forming an altered portion 13.

[0060] Due to the aforementioned alteration, the refractive index of the incident region of core 11 becomes a non-uniform refractive index distribution with a higher refractive index than that of core 11 (i.e., the refractive index distribution of the intermediate region of core 11 and the refractive index distribution of the exit region of core 11).

[0061] Due to this non-uniformity of the refractive index, the numerical aperture of the emitted laser light 30 from the output end of the fiber 10 saturates.

[0062] In Figure 5, the cross-section indicated by arrow CC is a cross-section in the incident region, located 450 mm from the incident end of fiber 10. The cross-section indicated by arrow DD is a cross-section in the intermediate region, located 1 m from the incident end of fiber 10. The cross-section indicated by arrow EE is a cross-section in the exit region, located 450 mm from the exit end of fiber 10.

[0063] Since the refractive index distributions in the CC, DD, and EE sections are the same, the refractive index distributions in the CC, DD, and EE sections will be explained below using Figure 6.

[0064] Figure 6 shows the radial refractive index distribution in the sections indicated by arrows CC, DD, and EE in Figure 5.

[0065] As shown in Figure 6, the refractive index of the core 11 in the CC, DD, and EE cross-sections is n0, which is the same as the refractive index of the core 11 of the fiber 10 before the heterogeneous treatment.

[0066] The refractive index of the cladding 12 in the CC, DD, and EE cross-sections is of the n1 step index type, the same as the refractive index of the cladding 12 of the fiber 10 before heterogeneous treatment. In other words, the refractive index distribution of the core in the CC, DD, and EE cross-sections is uniform.

[0067] In Figure 5, the section in the direction of arrow AA is the cross-section of the incident end of fiber 10. Figure 7 shows the radial refractive index distribution in the section in the direction of arrow AA in Figure 5.

[0068] As shown in FIG. 7, the refractive index distribution in the cross section taken along the line A-A has a non-uniform distribution, that is, a non-uniform refractive index distribution, which has a top-hat shape (i.e., a raised shape) with a refractive index n2 higher than the refractive index n0 at the center of the core 11.

[0069] Here, the diameter of the top-hat shape is determined by the light intensity distribution based on the beam profile of the incident laser light 20, the composition of the quartz of the core 11, and the irradiation time of the incident laser light 20.

[0070] On the other hand, the refractive index n2 is determined by the saturation of the alteration caused by the light intensity distribution based on the beam profile of the incident laser light 20 and the composition of the quartz of the core 11.

[0071] In FIG. 5, the cross section taken along the line B-B is a cross section at a position 150 mm away from the incident end of the fiber 10 in the incident region. FIG. 8 is a diagram showing the refractive index distribution in the radial direction in the cross section taken along the line B-B of FIG. 5.

[0072] As shown in FIG. 8, the refractive index distribution in the cross section taken along the line B-B has a non-uniform distribution, that is, a non-uniform refractive index distribution, which has at least one peak with a refractive index n3 satisfying n0 < n3 ≦ n2 at the center of the core 11.

[0073] The shape of the non-uniform refractive index distribution and the refractive index n3 are determined by the light intensity distribution based on the beam profile of the incident laser light 20, the composition of the quartz of the core 11, and the irradiation time of the incident laser light 20.

[0074] Hereinafter, it will be described how the numerical aperture of the output laser light 30 changes when the non-uniformity treatment is performed.

[0075] FIG. 9 is a graph showing the relationship between the irradiation time of the incident laser light 20 and the numerical aperture of the output laser light 30. In FIG. 9, the horizontal axis represents the irradiation time of the incident laser light 20, and the vertical axis represents the numerical aperture of the output laser light 30.

[0076] As shown in Figure 9, immediately after the start of the heterogeneity treatment, the numerical aperture of the emitted laser beam 30 is the same as that of the incident laser beam 20, which is 0.1. Subsequently, as the irradiation time of the incident laser beam 20 increases, the numerical aperture of the emitted laser beam 30 increases.

[0077] When the irradiation time of the incident laser beam 20 elapses for a predetermined period, the core 11 undergoes saturation, and consequently, the numerical aperture of the emitted laser beam 30 also saturates. As a result, the numerical aperture of the emitted laser beam 30 reaches the saturation numerical aperture. The saturation numerical aperture is, for example, 0.18. Here, since laser light with a numerical aperture of 0.2 or higher is not transmitted through the fiber 10, the numerical aperture of the emitted laser beam 30 becomes 0.2 or less.

[0078] Here, let NA1 be the numerical aperture of the emitted laser beam 30 after irradiation time T1, and NA2 be the numerical aperture of the emitted laser beam 30 after irradiation time T2. The change in numerical aperture is defined as △NA = {(NA2 - NA1) / NA1} × 100. The change in irradiation time is defined as △T = T2 - T1. Let △NA / △T be the rate of change of the numerical aperture of the emitted laser beam 30 per unit time.

[0079] The procedure for disintegrating the fiber 10 will be explained below using the flowchart in Figure 10. As shown in Figure 10, in step S11, the incident laser beam 20 is irradiated onto the incident end of the core 11, and the process proceeds to step S12.

[0080] In step S12, the numerical aperture and irradiation time of the emitted laser beam 30 are measured, and the process proceeds to step S13.

[0081] In step S13, the rate of change of the numerical aperture per unit time (ΔNA / ΔT) of the emitted laser beam 30 is calculated, and the process proceeds to step S14.

[0082] In step S14, it is determined whether the rate of change of the numerical aperture is less than or equal to a specified value. The default value is less than or equal to a value that depends on the tolerance of the change in the numerical aperture of the emitted laser beam 30 in laser processing using fiber 10, for example, 10 -2 Set to [% / h]

[0083] If the determination in step S14 is "YES", it is determined that the emitted laser beam 30 has reached the saturation numerical aperture, and the process is terminated. If the determination in step S14 is "NO", the process branches to step S11, and the irradiation of the incident laser beam 20 is continued.

[0084] The operation of the fiber 10 after the heterogeneous treatment will be described below. As shown in Figure 2, incident laser light 20 is incident on the core 11 at the incident end of the fiber 10. Here, the incident laser light 20 is, for example, a continuous wave laser light with a multimode beam intensity distribution, wavelength 405 nm, and output 1 kW. The incident laser light 20 is focused to 86.5%, with a diameter of 35 μm and a numerical aperture of 0.1 by a focusing lens (not shown), and is incident on the core 11 at the incident end of the fiber 10.

[0085] In this embodiment, the core 11 of the incident region of the fiber 10 is provided with a modified portion 13 in advance, such that the modification of the incident laser light 20 is saturated and the refractive index of the incident region has a non-uniform distribution.

[0086] Therefore, the incident laser light 20 that enters the incident region of fiber 10 is scattered in the altered section 13 and propagates within the core 11, becoming an exit laser light 30 with a numerical aperture of 0.2 or less, which is emitted from the exit end of fiber 10. The exit laser light 30 is guided to the laser head 3 and used for laser processing.

[0087] As described above, according to the fiber 10 of this embodiment, the incident region of the core 11 has a non-uniform refractive index distribution, which makes it possible to obtain an output laser beam 30 with a numerical aperture greater than that of the incident laser beam 20.

[0088] In this embodiment, the output of the incident laser beam 20 used for non-uniformity processing and the output of the incident laser beam 20 used for laser processing are the same, but the embodiment is not limited to this.

[0089] For example, the output of the incident laser beam 20 used for non-uniformity processing may be greater than the output of the incident laser beam 20 transmitted through the fiber 10 for laser processing. This makes it possible to shorten the irradiation time until the numerical aperture of the emitted laser beam 30 saturates.

[0090] Furthermore, in this embodiment, the wavelength of the incident laser light 20 used for the non-uniformity treatment was set to 400 nm, but other wavelengths (for example, ultraviolet wavelengths) of the incident laser light 20 may be used depending on the glass material of the core 11.

[0091] Furthermore, although the incident laser beam 20 used for the non-uniformity treatment and the incident laser beam 20 used for laser processing etc. after the completion of the non-uniformity treatment were described as being the same, it is not necessary for them to be the same incident laser beam 20, that is, laser beams emitted from the same laser oscillator 2. In other words, it is not necessary for the laser wavelength or focal diameter to be the same.

[0092] Furthermore, in this embodiment, the wavelength of the incident laser light 20 used for the non-uniformity treatment and the wavelength of the incident laser light 20 used for laser processing etc. after the completion of the non-uniformity treatment are both set to a single wavelength of 400 nm. However, the incident laser light 20 may consist of multiple wavelengths (for example, blue wavelength and near-infrared wavelength).

[0093] Furthermore, in this embodiment, the incident laser beam 20 used for the non-uniformity treatment is a continuous wave laser beam, but a pulsed wave laser beam may also be used.

[0094] Furthermore, in this embodiment, the light intensity distribution of the incident laser light 20 used for the heterogeneity treatment is a multimode beam intensity distribution, but a different light intensity distribution, such as a Gaussian mode intensity distribution, may also be used. This makes it possible to obtain a refractive index distribution in the incident region that has heterogeneity dependent on the light intensity distribution.

[0095] Furthermore, in this embodiment, the non-uniformity treatment is completed when the numerical aperture of the emitted laser light 30 becomes equal to the numerical aperture of the fiber 10. However, the treatment may also be completed when the numerical aperture of the emitted laser light 30 is a desired numerical aperture (for example, a numerical aperture that shows little change in numerical aperture over time).

[0096] Furthermore, in this embodiment, the fiber 10 is irradiated with incident laser light 20 during the non-uniformity treatment, but the same treatment can be performed even if, for example, both ends or one end of the fiber 10 are made into connectors. Moreover, the same treatment can be performed on a fiber 10 in which quartz blocks are fused to both ends or one end.

[0097] Embodiment 2 In the following description, the same reference numerals are used for parts that are the same as those in Embodiment 1, and only the differences will be described.

[0098] As shown in Figure 11, fiber 10 is constructed by welding together the first divided fiber 15 and the second divided fiber 16. In Figure 11, the welding points are represented by dotted lines.

[0099] The first divided fiber 15 constitutes the incident region of fiber 10. The numerical aperture of the first divided fiber 15 is, for example, 0.1. The longitudinal length of the first divided fiber 15 is, for example, 500 mm.

[0100] A modified portion 13 is provided in the core 11 of the first divided fiber 15. Due to the modified portion 13, the refractive index distribution of the core 11 in the first divided fiber 15 is non-uniform with respect to the longitudinal and radial directions of the first divided fiber 15.

[0101] The second split fiber 16 constitutes the intermediate region and the exit region of fiber 10. The numerical aperture of the second split fiber 16 is, for example, 0.2. The longitudinal length of the second split fiber 16 is, for example, 4.5 m.

[0102] The refractive index distribution of the core 11 of the second divided fiber 16 is uniform with respect to the longitudinal and radial directions of the second divided fiber 16. Here, the refractive index distribution of the core 11 in the second divided fiber 16 is the same with respect to the longitudinal and radial directions of the second divided fiber 16.

[0103] The non-uniform treatment of fiber 10 will be described below. As shown in Figure 12, the first divided fiber 15 before the non-uniform treatment is made of the same material and has the same configuration as the second divided fiber 16. In the first divided fiber 15 before the non-uniform treatment, the refractive index distribution is uniform in the longitudinal and radial directions of the first divided fiber 15. Furthermore, the refractive index distribution of the first divided fiber 15 before the non-uniform treatment is the same in the longitudinal and radial directions of the first divided fiber 15.

[0104] As shown in Figure 13, the first split fiber 15 before the non-uniformity treatment is irradiated with incident laser light 20, which is used as the laser light for the treatment, onto the core 11 at the incident end of the first split fiber 15.

[0105] Here, the incident laser beam 20 is, for example, a continuous wave laser beam with a multimode beam intensity distribution, wavelength 405 nm, and output power of 1 kW. The incident laser beam 20 is focused to 86.5%, with a diameter of 35 μm and a numerical aperture of 0.1 by a focusing lens (not shown), and is incident on the core 11 at the incident end of the first splitting fiber 15.

[0106] The incident laser beam 20 alters the quartz in the incident region of the core 11, creating an altered region 13.

[0107] Specifically, the refractive index of the core 11 of the first split fiber 15 increases locally and changes with the irradiation of the incident laser light 20 and the light intensity distribution of the incident laser light 20, resulting in a non-uniform refractive index distribution.

[0108] Due to this non-uniformity of refractive index, the numerical aperture of the emitted laser light 30 from the exit end of the first split fiber 15 becomes greater than the numerical aperture of the incident laser light 20, which is 0.1.

[0109] Then, this change in numerical aperture is monitored by measuring the output of the emitted laser beam 30 using an output measuring device (e.g., a power meter) not shown in the diagram.

[0110] As shown in Figure 14, the first divided fiber 15, which has undergone heterogeneity treatment, and the second divided fiber 16 are fused together to form a fiber 10 with the first divided fiber 15 as the incident region.

[0111] Figure 15 is a graph showing the relationship between the irradiation time of the incident laser beam 20 and the numerical aperture of the emitted laser beam 30. In Figure 15, the horizontal axis represents the irradiation time of the incident laser beam 20, and the vertical axis represents the numerical aperture of the emitted laser beam 30.

[0112] As shown in Figure 15, immediately after the start of the heterogeneity treatment, the numerical aperture of the emitted laser beam 30 is the same as that of the incident laser beam 20, which is 0.1. Subsequently, as the irradiation time of the incident laser beam 20 increases, the core 11 is altered, and the numerical aperture of the emitted laser beam 30 increases.

[0113] The output of the emitted laser beam 30 remains unchanged until the numerical aperture of the emitted laser beam 30 equals that of the first split fiber 15. However, after the numerical aperture of the emitted laser beam 30 equals that of the fiber 10, that is, when a portion of the incident laser beam 20 scattered due to alteration begins to leak from the core 11 into the cladding 12, a portion of the incident laser beam 20 cannot propagate through the core 11 and is lost. As a result, the output of the emitted laser beam 30 begins to decrease.

[0114] The procedure for disintegrating fiber 10 will be explained below using the flowchart in Figure 16. As shown in Figure 16, in step S21, the incident laser beam 20 is irradiated onto the incident end of the first split fiber 15, and the process proceeds to step S22.

[0115] In step S22, the output of the emitted laser beam 30 is measured, and the process proceeds to step S23.

[0116] In step S23, it is determined whether the output of the emitted laser light has fallen below a specified value. The specified value is, for example, 2%. If the determination in step S23 is "YES", the incidence of the incident laser light 20 is stopped and the process branches to step 24. If the determination in step S23 is "NO", the process branches to step S21.

[0117] In step S24, the first split fiber 15 and the second split fiber 16 are fusion spliced ​​together, and the process is completed.

[0118] The operation of the fiber 10 after the heterogeneous treatment will be described below. As shown in Figure 11, incident laser light 20 is incident on the core 11 at the incident end of the fiber 10. Here, the incident laser light 20 is, for example, a continuous wave laser light with a wavelength of 405 nm and an output of 1 kW, and a multimode beam intensity distribution. The incident laser light 20 is focused to 86.5%, with a diameter of 35 μm and a numerical aperture of 0.1 by a focusing lens (not shown), and is incident on the core 11 at the incident end of the fiber 10.

[0119] Because the refractive index of the incident region of the core 11 has a non-uniform distribution, the incident laser beam 20 is scattered in the altered section 13 and propagates within the core 11, becoming an emitted laser beam 30 with a numerical aperture of 0.2, equal to the numerical aperture of the fiber 10, and is emitted from the exit end of the fiber 10. The emitted laser beam 30 is guided to the laser head 3 and used for laser processing.

[0120] As described above, according to the fiber 10 of this embodiment, the incident region of the core 11 has a non-uniform refractive index distribution, which makes it possible to obtain an output laser beam 30 with a numerical aperture greater than that of the incident laser beam 20.

[0121] Furthermore, by dividing the fiber 10 into a first divided fiber 15 and a second divided fiber 16, the non-uniformity treatment of the fiber 10 can be performed in parallel, improving work efficiency. In addition, since the first divided fiber 15 is shorter in length than the second divided fiber 16, it becomes easier to handle the first divided fiber 15 when performing the non-uniformity treatment.

[0122] Embodiment 3 As shown in Figure 17, fiber 10 is constructed by welding together a first divided fiber 15 and a second divided fiber 16. In Figure 17, the welded area is represented by an outline.

[0123] The first divided fiber 15 constitutes the incident region of fiber 10. The numerical aperture of the first divided fiber 15 is, for example, 0.1. The longitudinal length of the first divided fiber 15 is, for example, 500 mm.

[0124] A modified portion 13 is provided in the core 11 of the first divided fiber 15. Due to the modified portion 13, the refractive index distribution of the core 11 in the first divided fiber 15 is non-uniform with respect to the longitudinal direction of the first divided fiber 15.

[0125] The second split fiber 16 constitutes the intermediate region and the exit region of fiber 10. The numerical aperture of the second split fiber 16 is, for example, 0.2. The longitudinal length of the second split fiber 16 is, for example, 4.5 m.

[0126] The refractive index distribution of the core 11 of the second divided fiber 16 is uniform with respect to the longitudinal and radial directions of the second divided fiber 16. Here, the refractive index distribution of the core 11 in the second divided fiber 16 is the same with respect to the longitudinal and radial directions of the second divided fiber 16.

[0127] The non-uniform treatment of fiber 10 will be described below. As shown in Figure 18, the first divided fiber 15 before the non-uniform treatment is made of the same material and has the same configuration as the second divided fiber 16. In the first divided fiber 15 before the non-uniform treatment, the refractive index distribution is uniform in the longitudinal and radial directions of the first divided fiber 15. Furthermore, the refractive index distribution of the first divided fiber 15 before the non-uniform treatment is the same in the longitudinal and radial directions of the first divided fiber 15.

[0128] As shown in Figure 18, when the first divided fiber 15, before the heterogeneous treatment, is irradiated with the drawing laser beam 25 as the processing laser beam onto the core 11 of the first divided fiber 15, the quartz in the incident region of the core 11 is altered and an altered portion 13 is generated (see Figure 19).

[0129] Here, the drawing laser beam 25 is, for example, a pulsed laser beam with a wavelength of 355 nm, a peak power of 500 W, and a pulse width of 10 ns. The drawing laser beam 25 is focused to a diameter of 50 μm with an 86.5% efficiency by a focusing lens (not shown).

[0130] Here, the drawing laser beam 25 is moved from the side of the first divided fiber 15 toward the core 11, and irradiated toward the core 11 while moving toward a predetermined length, for example, 200 mm, in the longitudinal direction from the incident end to the exit end of the first divided fiber 15.

[0131] At this time, the wavelength of the drawing laser beam 25 is 355 nm, which is in the ultraviolet region. On the other hand, the wavelength of the incident laser beam 20, which is the laser beam transmitted for use in laser processing, is 355 nm, which is the blue wavelength in the visible region.

[0132] Specifically, when core 11 is composed of quartz, absorption is greater in the ultraviolet region compared to the visible region, and ultraviolet laser light has a higher photon energy than visible laser light. Therefore, breaking and rearranging more Si-O bonds in quartz easily causes alteration of the quartz, i.e., a change in refractive index.

[0133] In other words, by using a marking laser beam 25 with a wavelength that is more likely to cause alteration of quartz, the processing time can be shortened. Irradiation with such marking laser beam 25 alters the incident region of the core 11, generating an altered area 13.

[0134] The end face irradiated with the drawing laser beam 25 becomes the incident end of the fiber 10. Due to this alteration, the refractive index of the core 11 is uniform in the radial direction of the fiber 10, but from the incident side, regions with a high refractive index in the longitudinal direction and regions with an untreated refractive index are created.

[0135] As shown in Figure 19, the incident laser beam 20 incident on the fiber 10 is a continuous wave laser beam with a wavelength of 405 nm and an output of 1 kW. The incident laser beam 20 is focused to 86.5%, with a diameter of 35 μm and a numerical aperture of 0.1 by a focusing lens (not shown), and is incident on the core 11 at the incident end of the fiber 10, propagates, and is emitted as the exit laser beam 30 from the exit end of the fiber 10.

[0136] The incident laser beam 20 is the same as the incident laser beam 20 described in Embodiment 1. The numerical aperture of the output laser beam 30 is measured by a numerical aperture measuring device (e.g., a power meter with an aperture) not shown. The beam is altered by the drawing laser beam 25 until it reaches a saturation numerical aperture (e.g., 0.18).

[0137] As shown in Figure 20, a fiber 10 is formed with the first divided fiber 15, which has undergone heterogeneity treatment, and a second divided fiber 16, which has not undergone heterogeneity treatment, by fusing them together (see Figure 21).

[0138] In Figure 21, the cross-section along the GG arrow is a cross-section located 300 mm away from the incident end of fiber 10 in the incident region.

[0139] Figure 22 shows the radial refractive index distribution in the cross-section viewed along the GG arrow in Figure 21. The refractive index of the core 11 in the cross-section viewed along the GG arrow is n0, which is the same as the refractive index of the core 11 of the fiber 10 before the heterogeneous treatment.

[0140] The refractive index of the cladding 12 in the cross-section along the arrow GG is of the n1 step index type, the same as the refractive index of the cladding 12 of the fiber 10 before the heterogeneous treatment. In other words, the refractive index distribution of the core 11 in the cross-section along the arrow GG is uniform.

[0141] In Figure 21, the cross-section in the direction of the FF arrow is the cross-section of the incident end of fiber 10. Figure 23 shows the radial refractive index distribution in the cross-section in the direction of the FF arrow in Figure 21.

[0142] As shown in Figure 23, the refractive index distribution in the cross-section along the FF arrow is a uniform distribution with a flat shape (i.e., a flat surface shape) with a refractive index n4 greater than n0. The diameter of the flat shape is equal to that of the core 11. The refractive index n4 is determined by the light intensity distribution of the drawing laser beam 25, the quartz composition of the core 11, and the irradiation time of the drawing laser beam 25.

[0143] The following explains how the numerical aperture of the emitted laser beam 30 changes when a heterogeneous treatment is performed.

[0144] Figure 24 is a graph showing the relationship between the number of times the drawing laser beam 25 is emitted and the numerical aperture of the emitted laser beam 30. In Figure 24, the horizontal axis represents the number of times the drawing laser beam 25 is emitted, that is, the number of times the drawing laser beam 25 has traveled 200 mm from the input end of the fiber 10 while emitting light. The vertical axis represents the numerical aperture of the emitted laser beam 30.

[0145] As shown in Figure 24, the numerical aperture of the emitted laser beam 30 increases as the number of irradiations of the drawing laser beam 25 increases. The drawing laser beam 25 is focused to 86.5% and a diameter of 50 μm by a focusing lens (not shown).

[0146] The drawing laser beam 25 is irradiated from the side of the fiber 10, moving along the longitudinal direction from the input end to the output end of the fiber 10 for a predetermined length, for example, 200 mm, thereby causing uniform alteration of the core 11 in the radial direction.

[0147] The procedure for disintegrating fiber 10 will be explained below using the flowchart in Figure 25. As shown in Figure 25, in step S31, irradiation of the incident laser light 20 to the incident end of the first split fiber 15 is started, and the process proceeds to step S32.

[0148] In step S32, the numerical aperture and irradiation time of the emitted laser beam 30 are measured, and the process proceeds to step S33.

[0149] In step S33, the irradiation of the drawing laser beam 25 is started, and the process proceeds to step S34.

[0150] In step S34, the drawing laser beam 25 is irradiated from the side of the first divided fiber 15, along the longitudinal direction starting from the incident end of the first divided fiber 15, and then the device moves a specified amount, for example 200 mm, in the longitudinal direction from the incident end of the first divided fiber 15, and proceeds to step S35.

[0151] In step S35, the irradiation of the drawing laser beam 25 is stopped, and the process proceeds to step S36.

[0152] In step S36, the numerical aperture and irradiation time of the emitted laser beam 30 are measured, and the process proceeds to step S37.

[0153] In step S37, it is determined whether the change in the numerical aperture of the emitted laser light 30 has reached a predetermined numerical aperture, for example, the saturation numerical aperture. If the determination in step S37 is "YES", the process branches to step S38. If the determination in step S37 is "NO", the process branches to step S39.

[0154] In step S38, the irradiation of the incident laser light 20 is stopped, and the process proceeds to step S40.

[0155] In step S39, the irradiation position of the drawing laser beam 25 is moved to the incident end, and the process proceeds to step S33, where irradiation with the drawing laser beam 25 is repeated until the change in the numerical aperture of the emitted laser beam 30 reaches, for example, the saturation numerical aperture.

[0156] In step S40, the first split fiber 15 and the second split fiber 16 are fusion spliced ​​together, and the process is completed.

[0157] The operation of the fiber 10 after the heterogeneous treatment will be described below. As shown in Figure 17, incident laser light 20 is incident on the core 11 at the incident end of the fiber 10. Here, the incident laser light 20 is, for example, a continuous wave laser light with a wavelength of 405 nm and an output of 1 kW. The incident laser light 20 is focused to 86.5%, with a diameter of 35 μm and a numerical aperture of 0.1 by a focusing lens (not shown), and is incident on the core 11 at the incident end of the fiber 10.

[0158] Because the refractive index of the incident region of the core 11 has a non-uniform distribution in the longitudinal direction of the fiber 10, the incident laser light 20 is scattered in the altered section 13 and propagates within the core 11, becoming an emitted laser light 30 with a desired numerical aperture (e.g., 0.18), which is emitted from the exit end of the fiber 10. The emitted laser light 30 is guided to the laser head 3 and used for laser processing.

[0159] As described above, according to the fiber 10 of this embodiment, since the incident end of the fiber 10 has a non-uniform refractive index distribution, it is possible to obtain an output laser beam 30 having a desired numerical aperture that is larger than the numerical aperture of the incident laser beam 20.

[0160] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the scope of the claims or equivalents thereof. [Industrial applicability]

[0161] As described above, the present invention is applicable to devices that transmit laser light using fibers. Specifically, this disclosure is applicable to laser processing machines, laser cutting machines, laser welding machines, laser printers, and the like. [Explanation of Symbols]

[0162] 1. Laser processing device 2. Laser Oscillator 10 Fibers 11 cores 12 clad 20 Incident laser light

Claims

1. A fiber having a core made of quartz and a cladding provided on the outer periphery of the core, which transmits laser light incident from the incident end of the core and exits from the exit end of the core, The region of a predetermined length extending longitudinally from the incident end of the core is defined as the incident region. The refractive index distribution of the core in the incident region differs from that of the core in at least one of the longitudinal and radial directions of the core, compared to the refractive index distribution of the core in the region excluding the incident region. fiber.

2. In the fiber of claim 1, The refractive index of the core in the incident region is higher than the refractive index of the core in the region excluding the incident region. fiber.

3. In the fiber of claim 1 or 2, The refractive index distribution of the core in the incident region is non-uniform in at least one of the longitudinal and radial directions of the core. fiber.

4. In the fiber of claim 1 or 2, The refractive index distribution of the core in the incident region is formed by the processing laser light irradiated onto the incident region. fiber.

5. In the fiber of claim 4, The output of the laser light used for the processing is the same as the output of the laser light transmitted from the input end to the output end of the core. fiber.

6. In the fiber of claim 4, The wavelength of the laser light used for the processing is 400 nm or more and less than 500 nm. fiber.

7. In the fiber of claim 3, The refractive index distribution of the core in the incident region is non-uniform in the longitudinal direction of the core. fiber.

8. A fiber according to claim 1 or 2, The system comprises a laser oscillator that emits the laser light incident on the fiber. Laser processing equipment.

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