Laser Equipment

Abstract

Provided is a laser device that makes it possible to detect return light propagating through a plurality of optical waveguides within an output optical fiber by means of a simple and inexpensive structure. This laser device 1 comprises: an output optical fiber 40 which includes a center core 41 and a ring core 43; a plurality of laser light sources 11, 12 which generate laser beams; input optical fibers 20, 30 through which laser beams propagate; an optical combiner 50 which is configured so as to optically connect the input optical fibers 20, 30 with the center core 41 and ring core 43 of the output optical fiber 40; a laser emission unit 60 which emits the laser beams that have been introduced into the center core 41 and ring core 43 of the output optical fiber 40; and a return light detection unit 7 which is capable of detecting both first return light returning toward the optical combiner 50 from the laser emission unit 60 via the center core 41 of the output optical fiber 40 and second return light returning toward the optical combiner 50 from the laser emission unit 60 via the ring core 43 of the output optical fiber 40.

Description

[Technical field]

[0001] The present invention relates to a laser device, and more particularly to a laser device capable of outputting laser light from an output optical fiber having a plurality of optical waveguides. [Background technology]

[0002] In the field of laser processing, in order to improve processing performance such as processing speed and processing quality, it is important to change the beam profile of the laser light irradiated to the workpiece in accordance with the material and thickness of the workpiece. From this perspective, in recent years, a technology has been developed that can change the beam profile of the laser light irradiated to the workpiece into a desired form by forming multiple optical waveguides in an output optical fiber and controlling the laser light introduced into each of these optical waveguides. For example, a laser device is known that performs laser processing by introducing laser light from different light sources into a central core of an output optical fiber and an outer core arranged around it (see, for example, Patent Document 1).

[0003] In such a laser device, it is considered that the laser light irradiated from the laser emission part to the workpiece may be reflected, for example, on the surface of the workpiece and return from the laser emission part to the inside of the laser device as return light. Since such return light may damage the components of the laser device, it is necessary to monitor the return light during the operation of the laser device. In particular, when an output optical fiber having multiple optical waveguides is used as described above, the return light propagates independently inside each optical waveguide, and a technology capable of detecting the return light propagating through multiple optical waveguides with a simple and inexpensive configuration is required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2018-524174 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the problems of the conventional technology, and has an object to provide a laser device that can detect return light propagating through a plurality of optical waveguides in an output optical fiber with a simple and inexpensive configuration. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a laser device capable of detecting return light propagating through a plurality of optical waveguides in an output optical fiber with a simple and inexpensive configuration. The laser device includes an output optical fiber including a first optical waveguide and a second optical waveguide, at least one first laser light source generating laser light, at least one first input optical fiber through which the laser light generated by the at least one first laser light source propagates, at least one second laser light source generating laser light, and at least one second input optical fiber through which the laser light generated by the at least one second laser light source propagates, the at least one first input optical fiber is optically connected to the first optical waveguide of the output optical fiber, and the at least one second input optical fiber is optically connected to the second optical waveguide, and the at least one first laser light source and the at least one second laser light source are configured to detect return light propagating through a plurality of optical waveguides in an output optical fiber. the first optical waveguide of the output optical fiber and the second optical waveguide of the output optical fiber; a laser emitting unit that emits the laser light introduced from the optical combiner to the first optical waveguide and the second optical waveguide of the output optical fiber; a first return optical fiber through which a first return light that returns from the laser emitting unit through the first optical waveguide of the output optical fiber toward the optical combiner propagates; a second return optical fiber through which a second return light that returns from the laser emitting unit through the second optical waveguide of the output optical fiber toward the optical combiner propagates; and a return light detection unit that is capable of detecting both the first return light that has propagated through the first return optical fiber and the second return light that has propagated through the second return optical fiber. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic block diagram showing the configuration of a laser device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a cross section of an output optical fiber of the laser device shown in FIG. 1 together with a refractive index profile along the radial direction. [Diagram 3] FIG. 3 is a perspective view showing an optical combiner of the laser device shown in FIG. [Figure 4] FIG. 4 is an exploded perspective view of the optical combiner shown in FIG. [Figure 5A] 5A is a plan view that illustrates a return light detection unit of the laser device illustrated in FIG. [Figure 5B] FIG. 5B is a cross-sectional view taken along line AA in FIG. 5A. [Figure 6] FIG. 6 is a graph showing an example of the relationship between the power of the return light propagating through the first return optical fiber and the second return optical fiber shown in FIG. 5B and the voltage detected by the photodetector. [Figure 7A] FIG. 7A is a plan view illustrating a schematic diagram of a return light detection unit of a laser device according to a second embodiment of the present invention. [Figure 7B] FIG. 7B is a cross-sectional view taken along line BB in FIG. 7A. [Figure 8] FIG. 8 is a cross-sectional view that illustrates a modified example of the return light detector shown in FIG. [Figure 9A] FIG. 9A is a plan view illustrating a schematic diagram of a return light detection unit of a laser device according to a third embodiment of the present invention. [Figure 9B] FIG. 9B is a cross-sectional view taken along line CC in FIG. 9A. [Figure 10] FIG. 10 is a graph showing an example of the relationship between the power of the return light propagating through the first return optical fiber and the second return optical fiber shown in FIG. 9B and the voltage detected by the photodetector. [Figure 11] FIG. 11 is a cross-sectional view that illustrates a return light detection unit of a laser device according to the fourth embodiment of the present invention. [Figure 12]FIG. 12 is a schematic block diagram showing the configuration of a laser device according to the fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of a laser device according to the present invention will be described in detail with reference to Figs. 1 to 12. In Figs. 1 to 12, identical or corresponding components are denoted with the same reference numerals, and duplicated explanations will be omitted. In addition, in Figs. 1 to 12, the scale and dimensions of each component may be exaggerated or some components may be omitted. In the following description, unless otherwise specified, terms such as "first" and "second" are used only to distinguish components from each other, and do not indicate a specific order or sequence.

[0009] Fig. 1 is a schematic block diagram showing the configuration of a laser device 1 in a first embodiment of the present invention. As shown in Fig. 1, the laser device 1 in this embodiment includes a plurality of first laser light sources 11 that generate laser light, a plurality of second laser light sources 12 that generate laser light, a first input optical fiber 20 through which the laser light generated by the first laser light source 11 propagates, a second input optical fiber 30 through which the laser light generated by the second laser light source 12 propagates, an output optical fiber 40 having a plurality of optical waveguides as described later, an optical combiner 2 that optically connects each of the first input optical fiber 20 and the second input optical fiber 30 to the optical waveguide of the output optical fiber 40, a laser emission unit 3 provided at the end of the output optical fiber 40, a control unit 4 that controls the laser light sources 11 and 12, and a stage 5 that holds the workpiece W. For example, a fiber laser or a semiconductor laser can be used as the laser light sources 11 and 12. The laser device 1 in this embodiment includes six first laser light sources 11 and five second laser light sources 12, but the numbers of the laser light sources 11, 12 are not limited to this.

[0010] The laser device 1 also includes a first return optical fiber 50, a second return optical fiber 60, and a return light detection unit 70 capable of detecting light propagating through the first return optical fiber 50 and the second return optical fiber 60. In this embodiment, unless otherwise specified, the direction from the laser light sources 11, 12 or the return light detection unit 70 toward the laser emission unit 3 is referred to as the "downstream side", and the opposite direction is referred to as the "upstream side".

[0011] 2 is a diagram showing a cross section of the output optical fiber 40 together with a refractive index distribution along the radial direction. As shown in FIG. 2, the output optical fiber 40 has a center core 41, an inner clad 42 that covers the periphery of the center core 41, a ring core 43 that covers the periphery of the inner clad 42, and an outer clad 44 that covers the periphery of the ring core 43. The refractive index of the inner clad 42 is lower than the refractive indexes of the center core 41 and the ring core 43, and the refractive index of the outer clad 44 is lower than the refractive index of the ring core 43. As a result, an optical waveguide (e.g., a first optical waveguide) through which light propagates is formed inside the center core 41, and an optical waveguide (e.g., a second optical waveguide) through which light propagates is formed inside the ring core 43. In this way, in this embodiment, the center core 41 and the ring core 43, which are independent optical waveguides, are concentrically arranged inside the output optical fiber 40. In addition, in this embodiment, the outer cladding 44 is formed around the ring core 43 as a low refractive index medium having a refractive index lower than that of the ring core 43. However, such a low refractive index medium is not limited to a coating layer such as the outer cladding 44. For example, an air layer may be formed around the ring core 43, and this air layer may be used as the low refractive index medium.

[0012] The outer diameters of the center core 41, the inner cladding 42, the ring core 43, and the outer cladding 44 of the output optical fiber 40 are important factors that determine the intensity distribution of the laser light L emitted from the laser emission part 3, but can be set arbitrarily according to the application and output specifications of the laser device 1. In addition, the refractive index of the inner cladding 42 and the refractive index of the outer cladding 44 may be the same or different.

[0013] 3 is a perspective view showing the optical combiner 2, and FIG. 4 is an exploded perspective view. As shown in FIG. 3 and FIG. 4, the optical combiner 2 includes a downstream end of a first input optical fiber 20, a downstream end of a first return optical fiber 50, a bridge fiber 80 to which the first input optical fiber 20 and the first return optical fiber 50 are connected, an intermediate optical fiber 90 connected to the bridge fiber 80, a downstream end of a second input optical fiber 30, a downstream end of a second return optical fiber 60, and an upstream end of an output optical fiber 40. The optical combiner 2 in this embodiment optically connects the downstream end of the first input optical fiber 20 to the center core 41 of the output optical fiber 40, and optically connects the downstream end of the second input optical fiber 30 to the ring core 43 of the output optical fiber 40.

[0014] The first input optical fiber 20 has a core 21 and a cladding 22 surrounding the core 21, and the refractive index of the cladding 22 is lower than that of the core 21. As a result, an optical waveguide through which light propagates is formed inside the core 21 of the first input optical fiber 20. Therefore, the laser light generated by the first laser light source 11 propagates through the core 21 of the first input optical fiber 20.

[0015] The first return optical fiber 50 has a core 51 and a cladding 52 surrounding the core 51, and the refractive index of the cladding 52 is lower than that of the core 51. As a result, an optical waveguide through which light propagates is formed inside the core 51 of the first return optical fiber 50. The same optical fiber as the first input optical fiber 20 may be used as this first return optical fiber 50.

[0016] 3 and 4, in this embodiment, five first input optical fibers 20A and five first return optical fibers 50 are connected to a bridge fiber 80 in a state in which they are arranged to surround one first input optical fiber 20B and contact the outer peripheral surface of the first input optical fiber 20B. At this time, the adjacent first input optical fibers 20 and first return optical fibers 50 are in contact with each other. The positions of the first return optical fiber 50 and the first input optical fiber 20B may be interchanged.

[0017] The bridge fiber 80 has a core 81 and a clad 82 that covers the periphery of the core 81. The refractive index of the clad 82 is lower than that of the core 81, and an optical waveguide through which light propagates is formed inside the core 81. For example, it is possible to form an air layer around the core 81 and use this air layer instead of the clad 82. The bridge fiber 80 having such a core-clad structure therein includes a first cylindrical portion 83 that extends with a constant outer diameter along the optical axis, a tapered portion 84 whose outer diameter gradually decreases from the first cylindrical portion 83 along the optical axis, and a second cylindrical portion 85 that extends with a constant outer diameter from the tapered portion 84 along the optical axis direction.

[0018] The downstream end of the first input optical fiber 20 and the downstream end of the first return optical fiber 50 are fusion-spliced ​​to the upstream end face (bridge entrance face) of the first cylindrical portion 83. The upstream end face of the intermediate optical fiber 90 is fusion-spliced ​​to the downstream end face of the second cylindrical portion 85. The size of the core 81 at the upstream end face of the bridge fiber 80 is large enough to contain the core 21 of the first input optical fiber 20 and the core 51 of the first return optical fiber 50 inside, and the first input optical fiber 20 and the first return optical fiber 50 are fusion-spliced ​​to the bridge fiber 80 so that the core 21 of the first input optical fiber 20 and the core 51 of the first return optical fiber 50 are located within the area of ​​the core 81 at the upstream end face of the bridge fiber 80. As a result, 90% or more (more preferably 95% or more) of the light propagating through the core 21 of the first input optical fiber 20 is optically coupled to the core 81 of the bridge fiber 80.

[0019] In this manner, the bridge fiber 80 is configured to propagate the laser light propagating through the core 21 of the first input optical fiber 20 inside the core 81, and reduce the beam diameter by the diameter-reducing section 84. In order to suppress reflection of the laser light when it is incident from the core 21 of the first input optical fiber 20 to the core 81 of the bridge fiber 80, it is preferable that the refractive index of the core 81 of the bridge fiber 80 is approximately the same as the refractive index of the core 21 of the first input optical fiber 20.

[0020] The intermediate optical fiber 90 has a core 91 and a clad 92 that covers the periphery of the core 91. The refractive index of the clad 92 is lower than that of the core 91, and an optical waveguide through which light propagates is formed inside the core 91. The size of the core 91 of the intermediate optical fiber 90 is equal to or larger than the size of the core 81 at the downstream end face of the bridge fiber 80, and the bridge fiber 80 and the intermediate optical fiber 90 are fusion spliced ​​such that the core 81 at the downstream end face of the bridge fiber 80 is located within the region of the core 91 of the intermediate optical fiber 90. As a result, 90% or more (more preferably 95% or more) of the light propagating through the core 81 of the bridge fiber 80 is optically coupled to the core 91 of the intermediate optical fiber 90. In this way, the intermediate optical fiber 90 is configured to propagate the laser light propagating from the bridge fiber 80 into the inside of its core 91. In addition, in order to suppress reflection when laser light is incident from the core 81 of the bridge fiber 80 to the core 91 of the intermediate optical fiber 90, it is preferable that the refractive index of the core 91 of the intermediate optical fiber 90 is approximately the same as the refractive index of the core 81 of the bridge fiber 80.

[0021] The second input optical fiber 30 has a core 31 and a cladding 32 surrounding the core 31, and the refractive index of the cladding 32 is lower than that of the core 31. As a result, an optical waveguide through which light propagates is formed inside the core 31 of the second input optical fiber 30. Therefore, the laser light generated by the second laser light source 12 propagates inside the core 31 of the second input optical fiber 30.

[0022] The second return optical fiber 60 has a core 61 and a cladding 62 surrounding the core 61, and the refractive index of the cladding 62 is lower than that of the core 61. As a result, an optical waveguide through which light propagates is formed inside the core 61 of the second return optical fiber 60. The same optical fiber as the second input optical fiber 30 may be used as the second return optical fiber 60.

[0023] The downstream end of the intermediate optical fiber 90, the downstream end of the second input optical fiber 30, and the downstream end of the second return optical fiber 60 are fusion-spliced ​​to the upstream end face of the output optical fiber 40. As shown in Figures 3 and 4, in this embodiment, five second input optical fibers 30 and five second return optical fibers 60 are connected to the output optical fiber 40 in a state in which they are arranged to surround the intermediate optical fiber 90 and contact the outer circumferential surface of the intermediate optical fiber 90. At this time, the adjacent second input optical fibers 30, second return optical fibers 60, and intermediate optical fibers 90 are in contact with each other.

[0024] The downstream end of the intermediate optical fiber 90 is fusion-spliced ​​to the upstream end of the output optical fiber 40 such that the core 91 of the intermediate optical fiber 90 is located within the region of the center core 41 of the output optical fiber 40. As a result, 90% or more (more preferably 95% or more) of the light propagating through the core 91 of the intermediate optical fiber 90 is optically coupled to the center core 41 of the output optical fiber 40. The downstream end of the second input optical fiber 30 and the downstream end of the second return optical fiber 60 are fusion-spliced ​​to the upstream end of the output optical fiber 40 such that the core 31 of the second input optical fiber 30 and the core 61 of the second return optical fiber 60 are located within the region of the ring core 43 of the output optical fiber 40. As a result, 90% or more (more preferably 95% or more) of the light propagating through the core 31 of the second input optical fiber 30 is optically coupled to the ring core 43 of the output optical fiber 40.

[0025] In such a configuration, the laser light generated by each of the first laser light sources 11 propagates through the core 21 of the first input optical fiber 20 and is introduced into the core 81 of the bridge fiber 80 of the optical combiner 2. The laser light introduced into the core 81 of the bridge fiber 80 is incident on the core 91 of the intermediate optical fiber 90 with its beam diameter reduced by the diameter reducing section 84. The laser light incident on the core 91 of the intermediate optical fiber 90 propagates through the core 91 and is introduced into the center core 41 of the output optical fiber 40. The laser light incident on the center core 41 of the output optical fiber 40 propagates inside the center core 41 and is irradiated from the laser emission section 3 as a part of the laser light L toward the workpiece W on the stage 5 (see FIG. 1).

[0026] Moreover, the laser light generated by each of the second laser light sources 12 propagates through the core 31 of the second input optical fiber 30 and is introduced into the ring core 43 of the output optical fiber 40 by the optical combiner 2. The laser light incident on the ring core 43 of the output optical fiber 40 propagates inside the ring core 43 and is emitted as a part of the laser light L from the laser emission part 3 toward the workpiece W on the stage 5 (see FIG. 1).

[0027] In this manner, in the laser device 1 of this embodiment, laser light L including laser light generated by the first laser light source 11 on the central side and laser light generated by the second laser light source 12 on the outside is irradiated from the laser emission section 3 toward the workpiece W on the stage 5.

[0028] Here, the control unit 4 can control the first laser light source 11 and the second laser light source 12, for example, by controlling the current supplied to the first laser light source 11 and the current supplied to the second laser light source 12. In this way, by controlling the first laser light source 11 and the second laser light source 12 by the control unit 4, the power of the laser light generated by the first laser light source 11 and the power of the laser light generated by the second laser light source 12 can be changed. Therefore, by controlling the first laser light source 11 and the second laser light source 12 by the control unit 4, the ratio of the intensity of the laser light introduced from the first laser light source 11 to the center core 41 of the output optical fiber 40 and the intensity of the laser light introduced from the second laser light source 12 to the ring core 43 of the output optical fiber 40 can be adjusted. That is, the control unit 4 in this embodiment is configured to be able to change the power of the laser light introduced from the first laser light source 11 to the center core 41 of the output optical fiber 40 and the power of the laser light introduced from the second laser light source 12 to the ring core 43. By controlling in this manner using the control unit 4, the power at the center of the laser light L output from the laser emission unit 3 of the laser device 1 and the power outside of it can be adjusted, and the profile of the laser light L can be easily changed.

[0029] 1, the output optical fiber 40 between the optical combiner 2 and the laser emission unit 3 is provided with a cladding mode elimination unit 6 for eliminating cladding mode light propagating through the outer cladding 44 of the output optical fiber 40. A known cladding mode elimination structure can be used as this cladding mode elimination unit 6, and detailed description thereof will be omitted. The cladding mode elimination unit 6 can eliminate unnecessary cladding mode light from the laser light propagating through the output optical fiber 40, thereby preventing such cladding mode light from adversely affecting the laser light L emitted from the laser emission unit 3.

[0030] For example, when the laser light L is irradiated from the laser emission unit 3 toward the workpiece W on the stage 5 to process the workpiece W, it is considered that the laser light L is reflected on the surface of the workpiece W, and this reflected light is recoupled to the output optical fiber 40 at the laser emission unit 3. Of such light, the light recoupled to the center core 41 of the output optical fiber 40 at the laser emission unit 3 (hereinafter referred to as "first return light") propagates from the laser emission unit 3 through the center core 41 toward the upstream optical combiner 2. Since the core 91 of the intermediate optical fiber 90 of the optical combiner 2 is optically connected to the center core 41 of the output optical fiber 40, this first return light is introduced from the center core 41 of the output optical fiber 40 into the core 91 of the intermediate optical fiber 90 of the optical combiner 2, and reaches the core 81 of the bridge fiber 80. As described above, the core 51 of the first return optical fiber 50 is optically connected to the core 81 of the bridge fiber 80, so that a portion of the first return light enters the core 51 of the first return optical fiber 50, propagates through the core 51 of the first return optical fiber 50, and reaches the return light detection unit 70 described above.

[0031] Moreover, the light recoupled with the ring core 43 of the output optical fiber 40 at the laser emission unit 3 (hereinafter referred to as "second return light") propagates from the laser emission unit 3 through the ring core 43 toward the upstream optical combiner 2. As described above, since the core 61 of the second return optical fiber 60 is optically connected to the ring core 43 of the output optical fiber 40, a part of the second return light enters the core 61 of the second return optical fiber 60, propagates through the core 61 of the second return optical fiber 60, and reaches the return light detection unit 70 described above.

[0032] Here, the return light detection unit 70 will be described in detail. FIG. 5A is a plan view showing the return light detection unit 70, and FIG. 5B is a cross-sectional view taken along line AA in FIG. 5A. As shown in FIGS. 5A and 5B, the return light detection unit 70 in this embodiment includes a fiber accommodating section 72 in which a groove 71 for accommodating the first return optical fiber 50 and the second return optical fiber 60 is formed, a resin 73 for fixing the first return optical fiber 50 and the second return optical fiber 60 in the groove 71 of the fiber accommodating section 72, a beam damper 74 connected to the end portions of the first return optical fiber 50 and the second return optical fiber 60, a frame 75 (shown in a see-through state in FIG. 5A) covering the fiber accommodating section 72 and the beam damper 74, and a photodetector 76 attached to a ceiling surface 75A of the frame 75. In this embodiment, for convenience, the +Z direction in FIG. 5B is referred to as "upper" or "upper", and the -Z direction is referred to as "lower" or "lower".

[0033] The fiber accommodating section 72 has a base 101, a first side wall 102 extending from the base 101 in the +Z direction (height direction), and a second side wall 103 extending in the +Z direction at a position spaced apart from the first side wall 102, and the first side wall 102 and the second side wall 103 extend parallel to each other along the X direction. The groove 71 of the fiber accommodating section 72 is defined by the base 101, the first side wall 102, and the second side wall 103, and extends along the X direction. The first return optical fiber 50 and the second return optical fiber 60 are accommodated inside the groove 71 along the X direction, and these return optical fibers 50, 60 are fixed by a resin 73 at both ends of the fiber accommodating section 72 in the X direction. In this way, by fixing the return optical fibers 50, 60 inside the groove 71 using the resin 73, the return optical fibers 50, 60 can be accurately and easily positioned.

[0034] The photodetector 76 is disposed near (above) the two return optical fibers 50, 60 housed in the groove 71 of the fiber housing section 72. In this embodiment, a photodetector capable of detecting Rayleigh scattered light is used as the photodetector 76. Such a photodetector capable of detecting Rayleigh scattered light has a good response speed and is capable of highly accurate detection. In addition, since Rayleigh scattered light has a power corresponding to the power of the light propagating through the optical fiber regardless of the guide direction of the light propagating through the optical fiber, a photodetector capable of detecting Rayleigh scattered light can detect the return light propagating inside the return optical fiber 50, 60 simply by disposing the photodetector on the side of the return optical fiber 50, 60. Therefore, by using a photodetector capable of detecting Rayleigh scattered light, it is not necessary to remove the coating of the return optical fiber 50, 60 and apply a high refractive index resin in order to extract the return light propagating through the return optical fiber 50, 60, and the return light can be detected with a simple configuration.

[0035] The return light detection unit 70 can simultaneously detect the first return light propagating upstream through the center core 41 of the output optical fiber 40 and the second return light propagating upstream through the ring core 43 of the output optical fiber 40. Therefore, even if the reflected light of the laser light L reflected on the surface of the workpiece W is recombined with the center core 41 and / or the ring core 43 of the output optical fiber 40, the amount of return light propagating through the center core 41 and / or the ring core 43 can be detected by the return light detection unit 70. In this way, the return light propagating through different optical waveguides can be detected by a single return light detection unit 70, so that the number of photodetectors 76 required in the return light detection unit 70 can be minimized and the detection circuit can be simplified. This makes it possible to detect the return light propagating through different optical waveguides with a simple and inexpensive configuration, accurately evaluate the effects of these return lights on the laser light sources 11, 12 and other components in the laser device 1, and operate the laser device 1 under safe conditions.

[0036] In general, the measured voltage when the Rayleigh scattered light of the light propagating through the optical fiber is measured by the photodetector is inversely proportional to the square of the distance from the center of the core of the optical fiber to the center of the photodetector. That is, the farther the optical fiber is placed from the photodetector, the lower the sensitivity of the photodetector to the light propagating through the optical fiber. In the example shown in FIG. 5B, the photodetector 76 and the return optical fibers 50 and 60 are placed so that the distance from the center C1 of the core 51 of the first return optical fiber 50 to the center P of the photodetector 76 is equal to the distance from the center C2 of the core 61 of the second return optical fiber 60 to the center P of the photodetector 76. Therefore, in the example shown in FIG. 5B, the sensitivity of the photodetector 76 to the first return light propagating through the first return optical fiber 50 is equal to the sensitivity of the photodetector 76 to the second return light propagating through the second return optical fiber 60.

[0037] For example, if the relationship between the power of the first return light propagating through the first return optical fiber 50 and the voltage detected by the photodetector 76 is as shown in Fig. 6, the relationship between the power of the second return light propagating through the second return optical fiber 60 and the voltage detected by the photodetector 76 will also be as shown in Fig. 6. For example, if configured to determine that an abnormality exists when the detected voltage of the photodetector 76 exceeds a threshold value of 0.5 V, it can be determined that an abnormality exists when the power of the return light propagating through the center core 41 and / or the ring core 43 exceeds 1000 W.

[0038] In this embodiment, as shown in FIG. 1, the detection signal of the return light detection unit 70 is input to the control unit 4. Therefore, the control unit 4 can appropriately control the first laser light source 11 and the second laser light source 12 according to the detection result of the return light detection unit 70. For example, when the control unit 4 determines that the amount of the first return light and / or the second return light is increasing from the detection signal of the return light detection unit 70 (when the detection voltage exceeds 0.5 V in the above example), the control unit 4 may control the first laser light source 11 and / or the second laser light source 12 to reduce the output of the first laser light source 11 and / or the second laser light source 12 or to stop the output. In this way, when an abnormality occurs in the laser device 1, the control unit 4 controls the first laser light source 11 and the second laser light source 12, so that the laser device 1 can be prevented from breaking down.

[0039] Furthermore, even if there is light that is recoupled with the outer cladding 44 of the output optical fiber 40 at the laser emission unit 3 and propagates upstream, such returned light can be removed by the cladding mode removal unit 6 because the above-mentioned cladding mode removal unit 6 is provided between the return light detection unit 70 and the laser emission unit 3. Therefore, it is possible to prevent such returned light from adversely affecting the detection result of the return light detection unit 70, and it is possible to improve the detection accuracy of the first return light and the second return light.

[0040] Here, since the intensity of the first return light is considered to be low compared to the laser light generated by the first laser light source 11, when the laser light generated by the first laser light source 11 propagates to the first return optical fiber 50, it becomes difficult to detect the first return light. In the optical combiner 2 of this embodiment, the first input optical fiber 20 connected to the first laser light source 11 and the first return optical fiber 50 are both optically connected to the center core 41 of the output optical fiber 40, so that the laser light generated by the first laser light source 11 is unlikely to enter the first return optical fiber 50. Therefore, in the return light detection unit 70, the influence of the laser light generated by the first laser light source 11 is reduced, and the first return light can be detected with high accuracy.

[0041] Similarly, the intensity of the second return light is considered to be low relative to the laser light and the laser light generated by the second laser light source 12. Therefore, when the laser light generated by the second laser light source 12 propagates to the second return optical fiber 60, it becomes difficult to detect the second return light. In the optical combiner 2 of this embodiment, the second input optical fiber 30 connected to the second laser light source 12 and the second return optical fiber 60 are both optically connected to the ring core 43 of the output optical fiber 40, so that the laser light generated by the second laser light source 12 is unlikely to enter the second return optical fiber 60. Therefore, in the return light detection unit 70, the influence of the laser light generated by the second laser light source 12 is reduced, and the second return light can be detected with high accuracy.

[0042] In addition, the optical combiner 2 in this embodiment is configured so that multiple first input optical fibers 20 are connected to the center core 41 of the output optical fiber 40 by a bridge fiber 80 having a reduced diameter portion 84 and an intermediate optical fiber 90, so that laser light from multiple first laser light sources 11 can be introduced into the center core 41 of the output optical fiber 40, and the power of the laser light output from the center core 41 of the output optical fiber 40 can be increased.

[0043] Fig. 7A is a plan view showing a schematic diagram of a return light detection section 170 of a laser device according to a second embodiment of the present invention, and Fig. 7B is a cross-sectional view taken along line BB in Fig. 7A. In the first embodiment described above, the first return optical fiber 50 and the second return optical fiber 60 are accommodated inside a single groove 71 formed in the fiber accommodating section 72, but in this embodiment, a fiber accommodating section 172 having two grooves 171A and 171B extending parallel to each other along the X direction is used, and the first return optical fiber 50 is accommodated in the groove 171A (first groove), and the second return optical fiber 60 is accommodated in the groove 171B (second groove).

[0044] More specifically, the fiber accommodating section 172 has a base 201, a first side wall 202 extending from the base 201 in the +Z direction (height direction), a second side wall 203 extending in the +Z direction at a position spaced apart from the first side wall 202, and an intermediate wall 204 extending in the +Z direction between the first side wall 202 and the second side wall 203. The first side wall 202, the second side wall 203, and the intermediate wall 204 extend parallel to each other along the X direction. The groove 171A of the fiber accommodating section 172 is defined by the base 201, the first side wall 202, and the intermediate wall 204, and extends along the X direction. The first return optical fiber 50 is accommodated inside the groove 171A along the X direction, and the first return optical fiber 50 is fixed by the resin 173A at both ends of the fiber accommodating section 172 in the X direction. The groove 171B of the fiber accommodating section 172 is defined by the base 201, the intermediate wall 204, and the second side wall 203, and extends along the X direction. The second return optical fiber 60 is accommodated inside the groove 171B along the X direction, and the second return optical fiber 60 is fixed by resin 173B at both ends in the X direction of the fiber accommodating section 172. In this way, the return optical fibers 50, 60 can be fixed in the separate grooves 171A, 171B, so that the return optical fibers 50, 60 can be positioned more accurately and simply.

[0045] In this case, in order to prevent the intermediate wall 204 of the fiber accommodating section 172 from preventing the Rayleigh scattered light of the return light propagating through the first return optical fiber 50 and the Rayleigh scattered light of the return light propagating through the second return optical fiber 60 from entering the photodetector 76, the height of the intermediate wall 204 from the base 201 may be made lower than the heights of the first side wall 202 and the second side wall 203 from the base 201, as shown in Fig. 8. With this configuration, the first return light and the second return light can be detected with higher accuracy.

[0046] Here, since the resistance to return light in the output optical fiber 40 may differ between the center core 41 and the ring core 43, for example, it may be desirable to detect an abnormality when return light exceeding 1000 W propagates through the center core 41, and an abnormality when return light exceeding 2000 W propagates through the ring core 43. The following embodiment is applicable to such a case.

[0047] Fig. 9A is a plan view showing a schematic diagram of a return light detection unit 270 of a laser device according to a third embodiment of the present invention, and Fig. 9B is a cross-sectional view taken along the line CC in Fig. 9A. In the second embodiment described above, the center P of the photodetector 76 is equidistant from the center C1 of the first return optical fiber 50 and the center C2 of the second return optical fiber 60, and the sensitivity of the photodetector 76 to the first return light propagating through the first return optical fiber 50 and the second return light propagating through the second return optical fiber 60 are equal, but in this embodiment, the sensitivity of the photodetector 76 to the second return light propagating through the second return optical fiber 60 is made lower than the sensitivity of the photodetector 76 to the first return light propagating through the first return optical fiber 50 by shifting the photodetector 76 in the Y direction.

[0048] For example, the relationship between the power of the first return light propagating through the first return optical fiber 50 and the power of the second return light propagating through the second return optical fiber 60, and the detection voltage by the photodetector 76 is as shown in Fig. 10. Therefore, in the case where the detection voltage of the photodetector 76 is configured to be determined to be abnormal when it exceeds a threshold value of 0.5 V, it can be determined to be abnormal when the power of the first return light propagating through the center core 41 exceeds 1000 W, and it can be determined to be abnormal when the power of the second return light propagating through the ring core 43 exceeds 2000 W, and it can be detected as abnormal according to the difference in resistance of the center core 41 and the ring core 43 to the return light.

[0049] Fig. 11 is a cross-sectional view showing a schematic diagram of a return light detection unit 370 according to the fourth embodiment of the present invention. In the second embodiment, the sensitivity of the photodetector 76 to the first return light and the second return light is adjusted by shifting the position of the photodetector 76 in the Y direction, but the sensitivity of the photodetector 76 can also be adjusted by the configuration shown in Fig. 11.

[0050] The return light detection unit 370 in this embodiment has a similar configuration to the second embodiment shown in FIG. 7, but one groove 171B of the fiber accommodating unit 372 is deeper than the other groove 171A, and the second return optical fiber 60 is accommodated and fixed in the deeper groove 171B. As a result, the second return optical fiber 60 is located in the -Z direction from the first return optical fiber 50, and the distance from the center C2 of the second return optical fiber 60 to the center P of the photodetector 76 is longer than the distance from the center C1 of the first return optical fiber 50 to the center P of the photodetector 76. Therefore, the sensitivity of the photodetector 76 to the second return light propagating through the second return optical fiber 60 is lower than the sensitivity of the photodetector 76 to the first return light propagating through the first return optical fiber 50.

[0051] In the second embodiment described above, the reflectance of light can be increased by gold plating the inner surface of one of the grooves 171A and 171B, so that, for example, the inner surface of the groove 171A is gold plated and a part of the first return light propagating through the first return optical fiber 50 is reflected by the inner surface of the groove 171A, making it easier for the first return light propagating through the first return optical fiber 50 to enter the photodetector 76 than the second return light propagating through the second return optical fiber 60. This makes it possible to make the sensitivity of the photodetector 76 to the first return light higher than the sensitivity of the photodetector 76 to the second return light.

[0052] Furthermore, since light can be absorbed by subjecting the inner surface of one of the grooves 171A and 171B to anodizing, for example, the inner surface of the groove 171B can be anodized to absorb part of the second return light propagating through the second return optical fiber 60 into the inner surface of the groove 171B, making it more difficult for the second return light propagating through the second return optical fiber 60 to enter the photodetector 76 than the first return light propagating through the first return optical fiber 50. This makes it possible to make the sensitivity of the photodetector 76 to the second return light lower than the sensitivity of the photodetector 76 to the first return light.

[0053] Fig. 12 is a schematic block diagram showing the configuration of a laser device 401 in the fifth embodiment of the present invention. In the laser device 1 shown in Fig. 1, the first return optical fiber 50 and the second return optical fiber 60 are directly connected to the return light detection unit 70, but as in this embodiment, the first return optical fiber 50 and the second return optical fiber 60 may be connected to an optical combiner 500, the return light propagating through the first return optical fiber 50 and the second return optical fiber 60 may be combined into an optical fiber 510 by the optical combiner 500, and the return light propagating through the optical fiber 510 may be detected by the return light detection unit 70.

[0054] In the above-described embodiment, the output optical fiber 40 has two optical waveguides consisting of a center core 41 and a ring core 43, but the output optical fiber 40 may have three or more optical waveguides, and the cross-sectional shape of the core is not limited to the circular or annular shape shown in the figures.

[0055] In the above-described embodiment, the wavelengths of the laser beams emitted from the plurality of first laser light sources 11 or the plurality of second laser light sources 12 may be different from each other.

[0056] In addition, the above-mentioned optical combiner 2 is an optical combiner configured by fusion splicing optical fibers, but the form of the optical combiner that connects the optical fibers 20, 30 to the center core 41 and the ring core 43 of the output optical fiber 40 is not limited to this. For example, it is also possible to configure the optical combiner using a mirror or a diffraction grating that selectively reflects a specific wavelength.

[0057] In the above-described embodiment, the resin 73, 173A, 173B for fixing the return optical fiber 50, 60 is disposed at both ends in the X direction of the groove 71, 171A, 171B of the fiber accommodating portion 72, 172, but this is not limited to this, and the resin 73, 173A, 173B may be disposed at another location of the groove 71, 171A, 171B of the fiber accommodating portion 72, 172, or the resin 73, 173A, 173B may be filled over the entire length of the groove 71, 171A, 171B.

[0058] As described above, according to one aspect of the present invention, there is provided a laser device capable of detecting return light propagating through a plurality of optical waveguides in an output optical fiber with a simple and inexpensive configuration. The laser device includes an output optical fiber including a first optical waveguide and a second optical waveguide, at least one first laser light source generating laser light, at least one first input optical fiber through which the laser light generated by the at least one first laser light source propagates, at least one second laser light source generating laser light, and at least one second input optical fiber through which the laser light generated by the at least one second laser light source propagates, the at least one first input optical fiber is optically connected to the first optical waveguide of the output optical fiber, and the at least one second input optical fiber is optically connected to the second optical waveguide, and the at least one first laser light source and the at least one second laser light source are configured to detect return light propagating through a plurality of optical waveguides in an output optical fiber. the first optical waveguide of the output optical fiber and the second optical waveguide of the output optical fiber; a laser emitting unit that emits the laser light introduced from the optical combiner to the first optical waveguide and the second optical waveguide of the output optical fiber; a first return optical fiber through which a first return light that returns from the laser emitting unit through the first optical waveguide of the output optical fiber toward the optical combiner propagates; a second return optical fiber through which a second return light that returns from the laser emitting unit through the second optical waveguide of the output optical fiber toward the optical combiner propagates; and a return light detection unit that is capable of detecting both the first return light that has propagated through the first return optical fiber and the second return light that has propagated through the second return optical fiber.

[0059] According to this configuration, even if the reflected light or the like is recombined with either the first optical waveguide or the second optical waveguide of the output optical fiber to become return light and propagates through the first optical waveguide or the second optical waveguide, the return light detector can detect the first return light propagating through the first optical waveguide and the second return light propagating through the second optical waveguide. In this way, since the return light propagating through different optical waveguides can be detected by a single return light detector, the number of detectors required in the return light detector can be minimized and the detection circuit can be simplified. As a result, the return light propagating through different optical waveguides can be detected with a simple and inexpensive configuration, and the effects of the return light on the laser light source and other components in the laser device can be accurately evaluated, and the laser device can be operated under safe conditions.

[0060] The return light detection unit preferably includes a photodetector capable of detecting both the Rayleigh scattered light of the first return light propagated through the first return optical fiber and the Rayleigh scattered light of the second return light propagated through the second return optical fiber. Since such a photodetector can detect the return light simply by being disposed on the side of the return optical fiber, there is no need to perform processing such as removing the coating of the return optical fiber and applying a high refractive index resin in order to extract the return light propagating through the return optical fiber, and the return light can be detected with a simple configuration.

[0061] The return light detection unit preferably includes a fiber accommodating section having at least one groove formed therein for accommodating the first return optical fiber and the second return optical fiber aligned therebetween, and a resin for fixing the first return optical fiber and the second return optical fiber inside the at least one groove of the fiber accommodating section. By fixing the return optical fiber inside the groove using a resin, the return optical fiber can be accurately and easily positioned.

[0062] The fiber accommodating section may have a base, a first side wall extending in the height direction from the base, a second side wall extending in the height direction from the base at a position spaced apart from the first side wall, and an intermediate wall extending from the base between the first side wall and the second side wall. The at least one groove of the fiber accommodating section may include a first groove defined by the base, the first side wall, and the intermediate wall, and accommodating the first return optical fiber along therein, and a second groove defined by the base, the intermediate wall, and the second side wall, and accommodating the second return optical fiber along therein. According to this configuration, the first return optical fiber and the second return optical fiber can be fixed in separate grooves, respectively, and therefore each return optical fiber can be positioned more accurately and simply.

[0063] The height of the intermediate wall from the base may be lower than the heights of the first and second side walls from the base. With this configuration, it is possible to suppress the intermediate wall from blocking the light entering the photodetector from the first and second return optical fibers, so that the first and second return lights can be detected with higher accuracy.

[0064] The output optical fiber may have a center core as the first optical waveguide formed at the center, an inner cladding having a refractive index lower than that of the center core and surrounding the center core, a ring core as the second optical waveguide having a refractive index higher than that of the inner cladding and surrounding the inner cladding, and a low refractive index medium having a refractive index lower than that of the ring core and surrounding the ring core. By controlling the laser light introduced into each optical waveguide of such an output optical fiber, the beam profile of the laser light irradiated to the processing object can be changed to a desired form.

[0065] The laser device may further include a control unit that controls the at least one first laser light source and the at least one second laser light source based on the first return light and the second return light detected by the return light detection unit. In this way, when an abnormality occurs in the laser device, the first laser light source and the second laser light source are controlled by the control unit, thereby preventing the laser device from breaking down.

[0066] Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and may be embodied in various different forms within the scope of the technical concept thereof.

[0067] This application is based on and claims priority to Japanese Patent Application No. 2021-203156, filed on December 15, 2021. The disclosure of this application is incorporated herein by reference in its entirety. [Industrial Applicability]

[0068] The present invention is preferably used in a laser device capable of outputting laser light from an output optical fiber having a plurality of optical waveguides. [Explanation of symbols]

[0069] 1,401 Laser equipment 2 Optical Combiner 3 Laser emission part 4. Control section 5 Stage 6 Cladding mode removal section 11 First laser light source 12 Second laser light source 20 First input optical fiber 30 Second input optical fiber 40 Output Fiber Optic 41 Center Core 42 Inner Cladding 43 Ring Core 44 Outer Cladding 50 First return optical fiber 60 Second return optical fiber 70,170,270,370 Return light detector 71 Groove 72,172 Fiber accommodating section 73,173A,173B Resin 74 Beam Dumper 75 Frame 76 Photodetector 80 Bridge Fiber 90 Intermediate optical fiber 101,201 base 102,202 First side wall 103,203 Second side wall 171A (First) Groove 171B (Second) Groove 204 Intermediate Wall 500 Optical Combiner 510 Optical Fiber L Laser light W Processing object

Claims

1. an output optical fiber including a first optical waveguide and a second optical waveguide; at least one first laser light source that generates a laser light; at least one first input optical fiber through which the laser light generated by the at least one first laser light source propagates; at least one second laser light source generating a laser light; at least one second input optical fiber through which the laser light generated by the at least one second laser light source propagates; an optical combiner configured such that the at least one first input optical fiber is optically connected to the first optical waveguide of the output optical fiber and the at least one second input optical fiber is optically connected to the second optical waveguide, and capable of introducing the laser light from the at least one first laser light source and the at least one second laser light source into the first optical waveguide and the second optical waveguide of the output optical fiber; a laser output unit that outputs the laser light introduced from the optical combiner into the first optical waveguide and the second optical waveguide of the output optical fiber; a first return optical fiber through which a first return light propagates, the first return light returning from the laser emission unit through the first optical waveguide of the output optical fiber toward the optical combiner; a second return optical fiber through which a second return light propagates, the second return light returning from the laser emission portion through the second optical waveguide of the output optical fiber toward the optical combiner; a return light detection unit capable of detecting both the first return light propagated through the first return optical fiber and the second return light propagated through the second return optical fiber; A laser device comprising:

2. The laser device according to claim 1, wherein the return light detection unit includes a photodetector capable of detecting both Rayleigh scattered light of the first return light propagating through the first return optical fiber and Rayleigh scattered light of the second return light propagating through the second return optical fiber.

3. The return light detection unit includes: a fiber accommodating section having at least one groove formed therein for accommodating the first return optical fiber and the second return optical fiber in an aligned manner; a resin for fixing the first return optical fiber and the second return optical fiber inside the at least one groove of the fiber accommodating portion; The laser device of claim 1 , comprising:

4. The fiber accommodating portion includes: A base and a first side wall extending in a height direction from the base; a second side wall extending in the height direction from the base at a position spaced from the first side wall; an intermediate wall extending from the base between the first side wall and the second side wall; having The at least one groove of the fiber receiving portion is a first groove defined by the base, the first side wall and the intermediate wall, the first groove receiving the first return optical fiber therein; a second groove defined by the base, the intermediate wall, and the second side wall, the second groove receiving the second return optical fiber therein; The laser device of claim 3 .

5. The laser device of claim 4 , wherein a height of the intermediate wall from the base is lower than a height of the first side wall and a height of the second side wall from the base.

6. The output optical fiber includes: a center core as the first optical waveguide formed at the center; an inner cladding having a refractive index lower than that of the center core and surrounding the center core; a ring core as the second optical waveguide, the ring core having a refractive index higher than that of the inner cladding and surrounding the inner cladding; a low refractive index medium having a refractive index lower than that of the ring core and surrounding the ring core; having 6. A laser device according to claim 1.

7. 6. The laser device according to claim 1, further comprising a control unit that controls the at least one first laser light source and the at least one second laser light source based on the first return light and the second return light detected by the return light detection unit.

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