Wavelength beam combining device, direct diode laser device, and laser processing machine

Abstract

To reduce optical loss in a wavelength beam coupling device.SOLUTION: The wavelength beam combining device includes a first optical member configured to separate the plurality of laser beams into a plurality of first polarized beams linearly polarized in a first polarization direction and a plurality of second polarized beams linearly polarized in a second polarization direction orthogonal to the first polarization direction, a first polarization conversion element configured to convert the plurality of second polarized beams into a plurality of third polarized beams linearly polarized in the first polarization direction, a plurality of first mirrors configured to reflect each of the plurality of first polarized beams toward a first diffraction position, a plurality of second mirrors configured to reflect each of the plurality of third polarized beams toward a second diffraction position, and a first diffraction element configured to receive and diffract the plurality of first polarized beams at the first diffraction position to form a first wavelength-combined beam in which the plurality of first polarized beams are coaxially superimposed. A second diffraction element configured to receive and diffract the plurality of third polarized beams at a second diffraction position to form a second wavelength-combined beam in which the plurality of third polarized beams are coaxially superimposed; SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a wavelength beam combining device, a direct diode laser device, and a laser processing machine. [Background technology]

[0002] High-power, high-brightness laser beams are used to perform processes such as cutting, drilling, and marking on various types of materials, as well as to weld metal materials. Some of the carbon dioxide gas laser and YAG solid-state laser machines that have traditionally been used for such laser processing are being replaced by fiber laser machines with high energy conversion efficiency. Laser diodes (hereafter simply referred to as LDs) are used as pump light sources for fiber laser machines. In recent years, with the increasing power output of LDs, technology is being developed that uses LDs not as pump light sources but as light sources for laser beams that directly irradiate materials for processing. This technology is called direct diode laser (DDL) technology.

[0003] Patent Document 1 discloses an example of a light source device that increases optical output by combining multiple laser beams with different peak wavelengths emitted from multiple LDs. Coaxially combining multiple laser beams with different wavelengths is called "wavelength beam combining (WBC)" or "spectral beam combining (SBC)" and can be used to increase the optical output and brightness of, for example, a DDL device.

[0004] Patent Document 2 discloses a wavelength beam combining device in which a plurality of diffraction gratings are arranged in series on an optical path. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent No. 6,192,062 [Patent Document 2] Patent Publication No. 2023-088438 Summary of the Invention [Problem to be solved by the invention]

[0006] There is a need for a wavelength beam combiner that can combine multiple laser beams with different peak wavelengths with little loss. [Means for solving the problem]

[0007] The wavelength beam combining device of the present disclosure is a wavelength beam combining device that combines a plurality of laser beams having mutually different peak wavelengths, and includes a first optical member that separates the plurality of laser beams into a plurality of first polarized beams that are linearly polarized in a first polarization direction and a plurality of second polarized beams that are linearly polarized in a second polarization direction orthogonal to the first polarization direction, a first polarization conversion element that converts the plurality of second polarized beams into a plurality of third polarized beams that are linearly polarized in the first polarization direction, a plurality of first mirrors that reflect each of the plurality of first polarized beams and direct them to a first diffraction position, and a first optical member that converts the plurality of third polarized beams into a plurality of third polarized beams that are linearly polarized in the first polarization direction. a first diffractive element that receives the plurality of first polarized beams reflected by the plurality of first mirrors at the first diffraction position and diffracts the beams to form a first wavelength combined beam in which the plurality of first polarized beams are coaxially superimposed; a second diffractive element that receives the plurality of third polarized beams reflected by the plurality of second mirrors at the second diffraction position and diffracts the beams to form a second wavelength combined beam in which the plurality of third polarized beams are coaxially superimposed; and a second optical member on which the first wavelength combined beam and the second wavelength combined beam are incident.

[0008] The direct diode laser device of the present disclosure includes the wavelength beam combining device and a laser light source that emits multiple laser beams in parallel.

[0009] The laser processing machine of the present disclosure comprises at least one of the direct diode laser devices, an optical transmission fiber coupled to the laser beam emitted from the at least one direct diode laser device, and a processing head connected to the optical transmission fiber. [Effects of the Invention]

[0010] According to an embodiment of the present disclosure, it is possible to provide a wavelength beam combining device that can combine multiple laser beams having different peak wavelengths with little loss. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a wavelength beam combining device according to an exemplary embodiment of the present disclosure. [Figure 2] FIG. 2 is a perspective view schematically showing an example of the configuration and function of a polarizing beam splitter. [Figure 3A] FIG. 3A is a perspective view schematically illustrating an example of the configuration of a diffraction grating. [Figure 3B] FIG. 3B is a cross-sectional view schematically illustrating an example of the configuration of a diffraction grating. [Figure 4] FIG. 4 is a diagram showing a schematic diagram of a modification of the wavelength beam combining device of FIG. [Figure 5] FIG. 5 is a schematic diagram illustrating another configuration of a wavelength beam combining device according to an exemplary embodiment of the present disclosure. [Figure 6] FIG. 6 is a schematic diagram illustrating yet another configuration of a wavelength beam combining device according to an exemplary embodiment of the present disclosure. [Figure 7] FIG. 7 is a schematic diagram illustrating yet another configuration of a wavelength beam combining device according to an exemplary embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram showing a schematic diagram of a diffraction region in the wavelength beam combining device of FIG. [Figure 9] FIG. 9 is a schematic diagram illustrating yet another configuration of a wavelength beam combining device according to an exemplary embodiment of the present disclosure. [Figure 10]FIG. 10 is a diagram showing a schematic diagram of a diffraction region in the wavelength beam combining device of FIG. [Figure 11] FIG. 11 is a diagram illustrating a configuration of a direct diode laser device according to an exemplary embodiment of the present disclosure. [Figure 12] FIG. 12 is a diagram illustrating a configuration of a laser processing machine according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a wavelength beam combining device, a direct diode laser device, and a laser processing machine according to embodiments of the present disclosure will be described with reference to the drawings. Parts that appear in multiple drawings with the same reference numerals indicate the same or equivalent parts.

[0013] Furthermore, the embodiments described below are examples to embody the technical idea of ​​the present invention, and do not limit the present invention. Furthermore, the size, material, shape, relative arrangement, etc. of components are intended to be illustrative and not to limit the scope of the present invention. The size and positional relationship of components shown in each drawing may be exaggerated to facilitate understanding.

[0014] In this specification and claims, polygons such as triangles and quadrilaterals are referred to as polygons, including shapes in which the corners of the polygon have been processed, such as by rounding, chamfering, removing corners, or rounding. Shapes in which processing has been applied not only to the corners (edges of the sides) but also to the middle portions of the sides are also referred to as polygons. In other words, shapes in which partial processing has been applied while retaining the polygonal base are included in the interpretation of "polygon" described in this specification and claims.

[0015] (Embodiment) [Wavelength beam combiner] <Embodiment 1> First, with reference to FIG. 1, a configuration example of a wavelength beam combining device according to a first embodiment of the present disclosure will be described.

[0016] FIG. 1 is a diagram schematically illustrating an example of the configuration of a wavelength beam combining device 100 according to this embodiment. For reference, each drawing, including FIG. 1, schematically illustrates mutually orthogonal X-, Y-, and Z-axes. The direction of the X-axis arrow is referred to as the +X direction, and the opposite direction is referred to as the -X direction. When there is no distinction between the ±X directions, they are simply referred to as the X direction. The same applies to the Y and Z directions. This does not limit the orientation of the wavelength beam combining device 100 during use, and the orientation of the wavelength beam combining device 100 is arbitrary.

[0017] First, the schematic configuration of the wavelength beam combining device 100 in the example of FIG. 1 will be described.

[0018] The wavelength beam combining device 100 is a device that combines multiple laser beams L having different peak wavelengths, and includes a first optical member 10 and a second optical member 12 that separate and / or combine light, a first polarization conversion element 20 and a second polarization conversion element 22 that change the polarization state of incident light and output it, a plurality of first mirrors 30A and a plurality of second mirrors 30B that reflect the incident light by changing its direction of travel, and a first diffraction element 40A and a second diffraction element 40B that each function as a diffraction grating.

[0019] The first optical member 10 splits the multiple laser beams L into multiple first polarized beams L1 that are linearly polarized in a first polarization direction (Y direction) and multiple second polarized beams L2 that are linearly polarized in a second polarization direction (X direction) that is orthogonal to the first polarization direction (Y direction). In the example of FIG. 1, the first optical member 10 is composed of a polarizing beam splitter BS. As will be described later, the first optical member 10 is not limited to a single member, and may include other optical elements in addition to the polarizing beam splitter BS, such as a member that forms a reflective surface and a member that shifts the optical path.

[0020] The first polarization conversion element 20 converts the plurality of second polarized beams L2 into a plurality of third polarized beams L3 that are linearly polarized in the first polarization direction (Y direction).

[0021] The first mirrors 30A are arranged to reflect the first polarized beams L1, respectively, and direct them to the first diffraction position P1.

[0022] The second mirrors 30B are arranged to reflect the third polarized beams L3 and direct them toward the second diffraction position P2.

[0023] The first diffraction element 40A receives the multiple first polarized beams L1 reflected by the multiple first mirrors 30A at a first diffraction position P1, and diffracts them to form a first wavelength combined beam CL1 in which the multiple first polarized beams L1 are coaxially superimposed.

[0024] The second diffraction element 40B receives the multiple third polarized beams L3 reflected by the multiple second mirrors 30B at a second diffraction position P2 and diffracts them to form a second wavelength combined beam CL2 in which the multiple third polarized beams L3 are coaxially superimposed.

[0025] 1, the second polarization conversion element 22 converts the polarization direction of the second-wavelength combined beam CL2 from a first polarization direction (Y direction) to a second polarization direction (X direction in the example of FIG. 1) perpendicular to the first polarization direction. The second polarization conversion element 22 may be arranged to convert the polarization direction of the first-wavelength combined beam CL1 from the first polarization direction (Y direction) to a direction (Z direction in the example of FIG. 1) perpendicular to the first polarization direction. The important point is that the second polarization conversion element 22 makes the polarization direction of the first-wavelength combined beam CL1 and the polarization direction of the second-wavelength combined beam CL2 orthogonal to each other, thereby enabling polarization combining (combining) by the second optical member 12.

[0026] The second optical member 12 is disposed so that the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 are incident thereon. In the example of Fig. 1, the second optical member 12 includes a polarizing beam splitter BS that coaxially combines the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 and outputs the combined beam as a third-wavelength combined beam CL3. When the second optical member 12 does not perform polarization combining using the polarizing beam splitter BS, the second optical member 12 may be configured by a condenser lens 50 without including the polarizing beam splitter BS. Such an example will be described later.

[0027] In the example of FIG. 1, the third-wavelength combined beam CL3 collected by the collecting lens 50 is incident on the core of the optical fiber 60 (is optically coupled).

[0028] In the wavelength beam combining device 100 of this embodiment, a single diffraction grating, rather than multiple ones, is placed on the optical paths of the polarized beams (L1, L3), thereby reducing optical loss due to diffraction.

[0029] Furthermore, in this embodiment, the multiple laser beams L may be incident parallel to the first optical member 10. Because the polarization separation characteristics of the first optical member 10 depend on the angle of incidence, by making the laser beam L incident parallel to the first optical member 10, it becomes possible to efficiently perform polarization separation of the laser beam L. The multiple light beams separated by the first optical member 10 can be made incident at a predetermined angle to the intended first diffractive element 40A and second diffractive element 40B by the multiple first mirrors 30A or the multiple second mirrors 30B, respectively.

[0030] The laser beam L and the components of the wavelength beam combining device 100 are described in detail below.

[0031] <Laser beam L> The peak wavelengths of the multiple laser beams L are different from one another and may be included in a predetermined wavelength range with a wavelength width of 50 nm or less, for example. The predetermined wavelength range corresponds to at least a portion of the wavelength range in which the object to be processed has high optical absorption. If the absolute value of the difference between the maximum and minimum peak wavelengths is, for example, 50 nm or less, optical system elements with wavelength-dependent optical properties, such as the polarizing beam splitter BS, polarization conversion elements 20 and 22, and condenser lens 50, can be commonly used for multiple light beams having different peak wavelengths, regardless of wavelength. For example, if the object to be processed is made of copper, the predetermined wavelength range may be, for example, 430 nm or more and 480 nm or less.

[0032] FIG. 1 illustrates three laser beams L with different peak wavelengths λ1, λ2, and λ3. The number of laser beams L may be two, four, or more. The greater the number of laser beams L, such as ten or more, the higher the output and power density of the wavelength-combined beam CL3 obtained by combining multiple laser beams L. Narrowing the intervals between the peak wavelengths of the multiple laser beams L allows for an increase in the number of laser beams L within a given wavelength range.

[0033] Hereinafter, the peak wavelength of the multiple laser beams L to be combined will also be referred to as λn. Here, "n" is an integer equal to or greater than 1 and is used as a numerical value to distinguish between the multiple laser beams L. In the example shown in FIG. 1, the relationship λ1<λ2<λ3 holds.

[0034] In Figure 1, each laser beam L is shown as a simple straight line. An actual laser beam L is a light beam that has an intensity distribution in a plane perpendicular to the direction of propagation. This intensity distribution can be approximated by a distribution function such as a Gaussian distribution in the plane perpendicular to the direction of propagation of the light beam. The diameter of the light beam is, for example, 1 / e 2It is defined as the size of a cross-sectional area having an intensity equal to or greater than 1 / 1000. e is the base of the natural logarithm. In this disclosure, the laser beam L is collimated by an optical system such as a collimator lens. In the drawings, the central axes of the light beams are represented by straight lines to schematically show the direction of travel of a collimated light beam such as the laser beam L. These straight lines may be considered to represent light rays passing through the center of each light beam.

[0035] The polarization state of the laser beam L may vary depending on, for example, the gain medium, resonator, and oscillation method of the laser light source. Furthermore, even if the laser beam L is in a specific polarization state when it is emitted from the semiconductor laser device, the polarization state may change or the laser beam may become depolarized while passing through a transmission medium such as an optical fiber.

[0036] Each laser beam L is, for example, in an unpolarized state. Such a laser beam L can be obtained, for example, by emitting each laser beam L from a semiconductor laser device via an optical fiber, as described above.

[0037] In this disclosure, "unpolarized" refers to light that is not linearly polarized in a specific direction. In this broad sense, "unpolarized" can also include circularly polarized light and elliptically polarized light. "Unpolarized" also includes a mixture of linearly polarized light, in which the polarization direction changes randomly or regularly with time or space.

[0038] <First optical member> In the example of FIG. 1, the first optical member 10 is a polarizing beam splitter BS. The polarizing beam splitter BS is made of, for example, quartz or synthetic quartz. The first optical member 10 has a polarization surface 10R that separates each incident laser beam L into light beams with different polarization states. The transmittance and reflectance of the polarization surface 10R vary depending on the polarization state of the laser beam L. The polarization surface 10R of the first optical member 10 selectively reflects a polarized light component that is linearly polarized in a predetermined direction and transmits a polarized light component that is linearly polarized in a direction perpendicular to the predetermined direction. The polarization surface 10R is provided with, for example, a dielectric multilayer film that has polarization dependency.

[0039] In the example shown in FIG. 1, the polarization plane 10R of the first optical member 10 is perpendicular to the XZ plane, and the normal to the polarization plane 10R is in a plane parallel to the XZ plane. The propagation direction of the laser beam L is parallel to the XZ plane. In this specification, light linearly polarized in the Y direction, which is perpendicular to the XZ plane, is referred to as "S-polarized light," and light linearly polarized in a direction parallel to the XZ plane is referred to as "P-polarized light." In this specification, the polarization direction of S-polarized light is also referred to as the "first polarization direction," and the polarization direction of P-polarized light is also referred to as the "second polarization direction." The second polarization direction is orthogonal to the first polarization direction.

[0040] In the accompanying drawings, as a general rule, a symbol with a small circle surrounding a cross symbol represents "S-polarized light," and a symbol with a double arrow represents "P-polarized light." The polarization direction of "P-polarized light" is parallel to the XZ plane but perpendicular to the direction of light propagation. Therefore, when the direction of light propagation remains parallel to the XZ plane and rotates due to reflection or diffraction, the polarization direction of "P-polarized light" also rotates within a plane parallel to the XZ plane. Therefore, in this specification, the "second polarization direction" is defined as a direction perpendicular to the direction of light propagation and perpendicular to the first polarization direction.

[0041] FIG. 2 is a perspective view that schematically illustrates an example of the configuration and function of a polarizing beam splitter BS that functions as the first optical member 10. Because FIG. 2 is a perspective view, the direction of "S-polarized light" is exceptionally indicated by a double-headed arrow. In the example of FIG. 2, a laser beam L containing S-polarized and P-polarized light propagates in the positive direction of the Z axis and enters the polarizing beam splitter BS. As shown in FIG. 2, the polarization plane 10R of the polarizing beam splitter BS reflects the S-polarized component of each laser beam L and transmits the P-polarized component. Therefore, the polarization plane 10R of the polarizing beam splitter BS splits the multiple laser beams L into multiple first polarized beams L1, each of which is S-polarized, and multiple second polarized beams L2, each of which is P-polarized. The multiple first polarized (S-polarized) beams L1 reflected by the polarization plane 10R of the polarizing beam splitter BS propagate in the -X direction, while the multiple second polarized (P-polarized) beams L2 transmitted through the polarization plane 10R of the polarizing beam splitter BS propagate in the +Z direction.

[0042] Each laser beam L may be incident on the polarization surface 10R at an incident angle of, for example, 40° to 50°, more preferably 42° to 48°. The closer the incident angle is to 45°, the higher the separation efficiency of each laser beam L into the corresponding first polarized beam L1 and second polarized beam L2.

[0043] If the multiple laser beams L incident on the polarizing beam splitter BS are "unpolarized," the laser beam L is separated into a first polarized (S-polarized) beam L1 and a second polarized (P-polarized) beam L2. However, even if the laser beam L is linearly polarized in a state where S-polarized and P-polarized light are superimposed, if the polarization direction is not parallel to either the X or Y direction, such a laser beam L is separated into a first polarized (S-polarized) beam L1 and a second polarized (P-polarized) beam L2. Also, even if the multiple laser beams L incident on the polarizing beam splitter BS are linearly polarized in different directions, the multiple laser beams L can be separated as a whole into a multiple first polarized (S-polarized) beam L1 and a multiple second polarized (P-polarized) beam L2. Therefore, unless all of the multiple laser beams L incident on the polarizing beam splitter BS are linearly polarized in either the X or Y direction, polarization separation by the polarizing beam splitter BS can be achieved, and the multiple laser beams L as a whole are interpreted as being "unpolarized."

[0044] In the example shown in FIG. 1, the first optical member 10 is a cube-type polarizing beam splitter BS, but is not limited to this example. The first optical member 10 may be a plate-type or other type of polarizing beam splitter BS. The first optical member 10 may also include an optical element such as a prism-type reflecting member in addition to the polarizing beam splitter. The first optical member 10 may also include an anti-reflection film provided on the polarizing beam splitter BS or other optical element.

[0045] The second optical member 12 in the example of FIG. 1 also includes a polarizing beam splitter BS similar to the polarizing beam splitter BS of the first optical member 10.

[0046] <First polarization conversion element> 1, the first polarization conversion element 20 converts the multiple second polarized beams L2, which are P-polarized light, into multiple third polarized beams L3, which are S-polarized light. The multiple third polarized (S-polarized) beams L3 travel in the +Z direction.

[0047] The first polarization conversion element 20 is made of, for example, quartz or synthetic quartz and may be a half-wave plate. A half-wave plate has birefringence and changes the phase difference between two orthogonal components of an electromagnetic wave traveling in the thickness direction. By arranging the slow axis or fast axis of the half-wave plate so that it forms a 45° angle with the polarization direction of P-polarized light, the half-wave plate can convert P-polarized light to S-polarized light.

[0048] In this way, the first optical member 10 and the first polarization conversion element 20 can obtain a plurality of first polarized beams L1 and a plurality of third polarized beams L3 that are linearly polarized in a specific direction from a plurality of laser beams L that are, for example, unpolarized as a whole. At this stage, the plurality of first polarized (S-polarized) beams L1 are composed of a plurality of laser beams that have different peak wavelengths and are not coaxially coupled. The same is true for the plurality of third polarized (S-polarized) beams L3.

[0049] 1, the polarization surface 10R of the first optical member 10 may reflect the P-polarized component and transmit the S-polarized component of each laser beam L. In this case, the multiple second polarized (P-polarized) beams L2 reflected by the polarization surface 10R of the first optical member 10 travel in the −X direction, and the multiple first polarized (S-polarized) beams L1 transmitted through the polarization surface 10R of the first optical member 10 travel in the +Z direction. The first polarization conversion element 20 is disposed at a position where the multiple second polarized (P-polarized) beams L2 pass through, and converts the multiple second polarized (P-polarized) beams L2 into multiple third polarized beams L3.

[0050] The phase difference formed by the half-wave plate depends on the wavelength of the incident light. Therefore, when three second polarized beams L2 with peak wavelengths λ1, λ2, and λ3 pass through the half-wave plate, a phase difference of exactly half wavelength is not formed at all peak wavelengths, and a P-polarized component remains in the S-polarized light converted from P-polarized light. Therefore, a P-polarized component remains in the multiple third polarized beams L3 output from the first polarization conversion element 20, and strictly speaking, elliptically polarized light may be included.

[0051] However, if all of the multiple peak wavelengths λn are within a relatively narrow range, for example, a range of 50 nm or less (preferably 10 nm or less), the difference in phase difference (wavelength dispersion) due to the half-wave plate is sufficiently small. Therefore, the second polarized beam L2 may mainly contain an S-polarized component and partially contain a P-polarized component.

[0052] The second polarization conversion element 22 can also have a configuration similar to that of the first polarization conversion element 20.

[0053] <First and second mirrors> As shown in FIG. 1, the multiple first mirrors 30A are arranged so as to reflect the multiple first polarized beams L1 and direct them toward the first diffraction position P1. A first diffraction grating 40 functioning as a first diffraction element 40A is arranged at the first diffraction position P1. The multiple first polarized beams L1 reflected by the multiple first mirrors 30A travel parallel to the XZ plane and are incident on a predetermined area (first diffraction position P1) of the first diffraction element 40A. Similarly, the multiple second mirrors 30B are arranged so as to reflect the multiple third polarized beams L3 and direct them toward the second diffraction position P2. A second diffraction grating 40 functioning as a second diffraction element 40B is arranged at the second diffraction position P2. The multiple third polarized beams L3 reflected by the multiple second mirrors 30B travel parallel to the XZ plane and are incident on a predetermined area (second diffraction position P2) of the second diffraction element 40B.

[0054] The respective positions and angles of the multiple first mirrors 30A and multiple second mirrors 30B are determined so that a first wavelength combined beam CL1 generated by diffraction by the first diffraction element 40A at the first diffraction position P1 and a second wavelength combined beam CL2 generated by diffraction by the second diffraction element 40B at the second diffraction position P2 are orthogonal within the second optical member 12.

[0055] Reflection by the plurality of first mirrors 30A and the plurality of second mirrors 30B does not change the polarization direction of the plurality of first polarized beams L1 and the plurality of third polarized beams L3, respectively.

[0056] The first mirror 30A and the second mirror 30B may be formed, for example, by providing a dielectric multilayer film with low optical loss on heat-resistant glass. The dielectric multilayer film has a reflectance of nearly 100% in a wavelength range called the stop band. If all of the multiple peak wavelengths λn are included in the stop band, the multiple first mirrors 30A and the multiple second mirrors 30B may be formed from the same dielectric multilayer film. If optical loss is not a consideration, the multiple first mirrors 30A and the multiple second mirrors 30B may be formed from a metal material.

[0057] <Diffraction element> In this embodiment, the first diffraction element 40A and the second diffraction element 40B have the same structure. Specifically, the first diffraction element 40A and the second diffraction element 40B are each composed of a diffraction grating 40 having the same structure. The diffraction grating 40 is formed of, for example, quartz or synthetic quartz. Hereinafter, the diffraction grating 40 including the first diffraction element 40A may be referred to as the "first diffraction grating," and the diffraction grating 40 including the second diffraction element 40B may be referred to as the "second diffraction grating," to distinguish them from each other.

[0058] 3A is a perspective view that schematically illustrates how an incident light beam 14A with a peak wavelength λn is incident on a diffraction grating 40, is diffracted, and forms diffracted light beams 14B. The number of diffracted light beams 14B that can be formed is not limited to one. For simplicity, FIG. 3A illustrates only one of multiple diffracted light beams 14B. The incident light beam 14A represents a light beam contained in each of the multiple first polarized light beams L1 or a light beam contained in each of the multiple third polarized light beams L3.

[0059] The incident angle of incident light ray 14A is denoted by αn. The "n" in the incident angle αn is the same integer as the "n" in the peak wavelength λn. The incident angle αn is the angle formed between the normal direction H on the diffractive surface of diffraction grating 40 and incident light ray 14A of peak wavelength λn. A large number of diffraction grooves extending in the Y direction are provided on the surface of diffraction grating 40.

[0060] 3A depicts an imaginary plane 44 parallel to the XZ plane. This imaginary plane 44 is a plane that includes the incident light beam 14A and the diffracted light beam 14B and is perpendicular to the diffraction grooves. Diffraction is a phenomenon (dispersion) in which the angle between the incident light beam 14A and the diffracted light beam 14B in the imaginary plane 44 changes depending on the wavelength.

[0061] If the diffraction angle of the diffracted light beam 14B is β, the relationship of the following formula 1 holds. sin(αn) + sin(β) = N·m·λn ···(1) Here, N is the number of diffraction grooves per mm of the diffraction grating 40, and m is the diffraction order. N can be, for example, 1000 to 5000 grooves / mm.

[0062] For example, if the diffraction order m is 1, the diffraction angle β is 45.0 degrees, N=2500, and the wavelength λn is 450 nm, the incident angle αn is 24.7 degrees. When multiple laser beams with different peak wavelengths λn are incident on the same position on the diffraction grating 40, by appropriately selecting the wavelength λn and the incident angle αn, it is possible to diffract the multiple laser beams with different peak wavelengths λn in the direction of the same diffraction angle β.

[0063] As described above, in this embodiment, the relationship λ1<λ2<λ3 holds. When multiple laser beams L with peak wavelengths λ1, λ2, and λ3 are incident on the diffraction grating 40 and form diffracted light at the same diffraction angle β, the relationship α1<α2<α3 holds for the incident angle αn.

[0064] FIG. 3B is a cross-sectional view schematically illustrating the main diffracted beams formed when a light beam I is incident on a transmission-type diffraction grating 40. FIG. 3B illustrates the reflected zeroth-order diffracted beam R-0, the reflected first-order diffracted beam R-1, the transmitted zeroth-order diffracted beam T-0, and the transmitted first-order diffracted beam T-1 formed by the diffraction grating 40. Even though the diffraction grating 40 is a transmission-type diffraction grating, the diffraction grating 40 used in this embodiment is configured to selectively generate a strong reflected first-order diffracted beam R-1. Therefore, the reflected zeroth-order diffracted beam R-0, the transmitted zeroth-order diffracted beam T-0, and the transmitted first-order diffracted beam T-1 generated by the transmission-type diffraction grating 40 are negligible. As a result, most of the laser beam incident on the diffraction grating is not absorbed by the material constituting the diffraction grating 40, reducing light loss. Unlike transmission-type diffraction gratings, reflection-type diffraction gratings include reflective components such as dielectric multilayer films or mirrors, and light absorption by these components cannot be ignored. Therefore, with a reflective diffraction grating, if the intensity of the incident laser beam increases, heat generated by light absorption may degrade the performance of the diffraction grating. The substrate of the diffraction grating 40 may be formed from a material with low absorption at the peak wavelength of the laser beam, such as quartz or synthetic quartz. The cross-sectional shape of the grating may be, for example, rectangular or trapezoidal.

[0065] A light absorbing member may be provided on the inner surface of the housing that houses the components of the wavelength beam combining device 100. The light absorbing member absorbs diffracted light beams other than the reflected first-order diffracted light beam R-1, thereby reducing the occurrence of stray light.

[0066] As described above, by appropriately selecting the wavelength λn and the incident angle αn, multiple first polarized beams L1 with different peak wavelengths λn can be diffracted in the direction of the same diffraction angle β. The same is true for multiple third polarized beams L3 with different peak wavelengths λn.

[0067] In this embodiment, an S-polarized polarized beam L1 or an S-polarized polarized beam L3 is incident on the diffraction grating 40. If the diffraction grating 40 has polarization dependency, when an unpolarized laser beam is incident, the diffraction efficiency will decrease depending on the polarization component. In a diffraction grating 40 having multiple diffraction grooves parallel to the Y direction, which is the first polarization direction, the diffraction efficiency of S-polarized light is higher than the diffraction efficiency of P-polarized light. Therefore, the diffraction grating 40 can effectively diffract the S-polarized polarized beams L1 and L3.

[0068] When the laser beam L has a spectral width Δλn approximately centered at the peak wavelength λn, the smaller the spectral width Δλn, the better. If the spectral width Δλn is wide, the diffraction angle β will have a large width, which will impart a width to the wavelength-combined beams CL1 and CL2 in the propagation direction. The spectral width Δλn is set to, for example, 0.3 nm or less. By combining multiple laser beams L with narrow spectral widths Δλn, wavelength-combined beams CL1 and CL2 containing multiple peak wavelengths in a predetermined wavelength range can be formed, thereby effectively increasing their output and optical density.

[0069] In the example of Fig. 1, diffractive element 40A or 40B, which is made up of a single diffraction grating 40, is placed on the same optical path. Because diffraction by diffraction grating 40 generates unwanted diffracted light rays, placing one diffraction grating on the same optical path can reduce optical loss compared to placing two diffraction gratings on the same optical path.

[0070] In the example of FIG. 1, the first diffractive element 40A is positioned to emit the first-wavelength combined beam CL1 in the −X direction from the first diffraction position P1. In contrast, the second diffractive element 40B is positioned to emit the second-wavelength combined beam CL2 in the +Z direction from the second diffraction position P2. More specifically, the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 are on the same plane parallel to the XZ plane and are orthogonal to each other. The positions and orientations of the first diffractive element 40A and the second diffractive element 40B are determined so that the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 are incident at an angle of 45° with respect to the polarization plane 12R of the second optical member 12 (polarizing beam splitter BS).

[0071] In this embodiment, the first diffractive element 40A and the second diffractive element 40B are arranged to orthogonally intersect the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2, and cause the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 to be incident on the second optical member 12 from directions orthogonal to each other.

[0072] <Second polarization conversion element> 1, the second polarization conversion element 22 converts the second-wavelength combined beam CL2, which is S-polarized, into P-polarized light. As a result, the polarization direction of the first-wavelength combined beam CL1 and the polarization direction of the second-wavelength combined beam CL2 are orthogonal to each other. The configuration of the second polarization conversion element 22 can be similar to the configuration of the first polarization conversion element 20.

[0073] <Second optical member> 1, the second optical member 12 is composed of a polarizing beam splitter BS having a polarization plane 12R. Similar to the polarization plane 10R, this polarization plane 12R reflects S-polarized light and transmits P-polarized light. The second optical member 12 performs polarization synthesis of the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2. The second optical member 12 coaxially combines the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2, and outputs the combined beam in the +Z direction as a third-wavelength combined beam CL3.

[0074] The polarization plane 12R of the second optical member 12 may transmit S-polarized light and reflect P-polarized light. In this case, the second polarization conversion element 22 on the optical path of the second-wavelength combined beam CL2 may be moved onto the optical path of the first-wavelength combined beam CL1. If the position of the second polarization conversion element 22 is not changed, the third-wavelength combined beam CL3 emitted from the second optical member 12 travels in the −X direction, and therefore a condenser lens 50 and an optical fiber 60 may be disposed on the optical path of the third-wavelength combined beam CL3.

[0075] <Condenser lenses and optical fibers> The condenser lens 50 is disposed at a position where it receives the third-wavelength combined beam CL3, and condenses the third-wavelength combined beam CL3 before inputting it into the optical fiber 60. The optical axis of the condenser lens 50 is parallel to the traveling direction of the third-wavelength combined beam CL3. The focal point of the condenser lens 50 is located at the incident end surface of the optical fiber 60. The condenser lens 50 may be a single lens or a combination of multiple lenses. The condenser lens 50 is formed of, for example, quartz or synthetic quartz.

[0076] The optical fiber 60 emits the third-wavelength combined beam CL3 incident on its incident end face from its output end face. The optical fiber 60 has an arbitrary length and is bendable, so the third-wavelength combined beam CL3 can be emitted in an arbitrary direction from the output end face of the optical fiber 60.

[0077] <Modification of the First Embodiment> FIG. 4 shows the configuration of a wavelength beam combining device 110, which is a modified example of the embodiment shown in FIG. 1. The difference between the configuration of the wavelength beam combining device 110 shown in FIG. 4 and the configuration of the wavelength beam combining device 100 shown in FIG. 1 is the arrangement of the laser beams L with peak wavelengths λ1, λ2, and λ3 (λ1<λ2<λ3). In the wavelength beam combining device 100 shown in FIG. 1, the laser beam L with the shortest peak wavelength λ1 is located on the upper side (+X direction) of the figure, and the laser beam L with the longest peak wavelength λ3 is located on the lower side (-X direction) of the figure. In contrast, in the wavelength beam combining device 110 shown in FIG. 4, the laser beam L with the longest peak wavelength λ3 is located on the upper side (+X direction) of the figure, and the laser beam L with the shortest peak wavelength λ1 is located on the lower side (-X direction) of the figure.

[0078] Depending on the difference in the arrangement of the laser beams L, the arrangement of the multiple first mirrors 30A and the arrangement of the multiple second mirrors 30B are arranged so that the angle of incidence αn when the first polarized beam L1 is incident on the first diffraction element 40A and the angle of incidence αn when the third polarized beam L3 is incident on the second diffraction element 40B satisfy α1<α2<α3.

[0079] According to the configuration of Figure 4, it is possible to make the optical path length difference of the optical paths of the first polarized beam L1 and the third polarized beam L3 approximately the same, and it is possible to make the beam diameters at the first diffraction position P1 and the second diffraction position P2 approximately the same, thereby making it possible to improve the coupling efficiency to the optical fiber 60.

[0080] 1 and 4, the two diffraction gratings 40 are arranged so that the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 are orthogonal to each other. The polarization plane 12R of the polarizing beam splitter BS in the second optical member 12 is located at the position where the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 are orthogonal to each other. In this manner, the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 are incident on the second optical member 12 from directions orthogonal to each other to perform polarization combining. However, the configuration for performing polarization combining of the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 is not limited to the examples in FIGS. 1 and 4.

[0081] <Embodiment 2> 5 shows a configuration example of a wavelength beam combining device 120 according to another embodiment of the present disclosure. In the wavelength beam combining device 120, two diffraction gratings 40 are arranged to make the first wavelength combined beam CL1 and the second wavelength combined beam CL2 parallel, and the first wavelength combined beam CL1 and the second wavelength combined beam CL2 are incident on the second optical member 12 from the same direction.

[0082] The configuration of the wavelength beam combining device 120 in Fig. 5 will be described below, with redundant explanations of components common to those of the wavelength beam combining device 100 in Fig. 1 being omitted.

[0083] Similar to the wavelength beam combining device 100 of FIG. 1, the wavelength beam combining device 120 of FIG. 5 includes a first optical member 10 and a second optical member 12 that separate and / or combine light, a first polarization conversion element 20 and a second polarization conversion element 22 that change the polarization state of the incident light and output the light, a plurality of first mirrors 30A and a plurality of second mirrors 30B that change the direction of travel of the incident light and reflect it, and a first diffraction element 40A and a second diffraction element 40B that each function as a diffraction grating 40.

[0084] The first optical member 10 has a reflecting surface 10M that reflects one of the multiple first polarized beams L1 and multiple second polarized beams L2 split by the first polarizing beam splitter BS. This reflecting surface 10M parallels the traveling direction of the multiple first polarized beams L1 and the multiple second polarized beams L2. In the example of FIG. 5, the reflecting surface 10M is part of an optical component integrated with the polarization plane 10R of the polarizing beam splitter BS and is parallel to the polarization plane 10R. Specifically, the polarization plane 10R is located on one slope of a prism member with a parallelogram cross section, and the reflecting surface 10M is located on the other slope. This eliminates the need for alignment to parallelize the first polarized beam L1 with respect to the multiple third polarized beams L3 obtained by converting the multiple second polarized beams L2 transmitted through the polarization plane 10R. However, the configuration of the first optical member 10 is not limited to this example. The reflecting surface 10M may be a separate optical component separated from the polarizing beam splitter BS. Furthermore, the reflecting surface 10M does not necessarily have to be parallel to the polarizing surface 10R.

[0085] In the wavelength beam combining device 120 of FIG. 5, the multiple first polarized beams L1 and the multiple third polarized beams L3 emitted from the first optical member 10 each travel in the +X direction and are reflected by the multiple first mirrors 30A and the multiple second mirrors 30B. The positions and orientations of the multiple first mirrors 30A are determined so as to direct the multiple first polarized beams L1 toward the first diffraction position P1. Similarly, the positions and orientations of the multiple second mirrors 30B are determined so as to direct the multiple third polarized beams L3 toward the second diffraction position P2. The first diffraction element 40A and the second diffraction element 40B are arranged in the same orientation. As a result, the first wavelength combined beam CL1 and the second wavelength combined beam CL2 travel parallel to each other in the same direction (the −X direction in the example of FIG. 5) from the first diffraction position P1 and the second diffraction position P2, respectively.

[0086] Note that the traveling direction of the first-wavelength combined beam CL1 from the first diffraction position P1 and the traveling direction of the second-wavelength combined beam CL2 from the second diffraction position P2 do not necessarily have to be parallel to the −X direction as long as they are parallel to each other. By changing the positions and orientations of the multiple first mirrors 30A and the first diffraction element 40A from the illustrated example and similarly changing the positions and orientations of the multiple second mirrors 30B and the second diffraction element 40B, it is possible to tilt the traveling direction of the first-wavelength combined beam CL1 and the traveling direction of the second-wavelength combined beam CL2 from the second diffraction position P2 from the X direction while maintaining them parallel to each other.

[0087] 5, the second optical member 12, like the first optical member 10, has a polarization plane 12R that transmits P-polarized light and reflects S-polarized light, and a reflection plane 12M parallel to the polarization plane 12R. The polarization direction of the second-wavelength combined beam CL2 emitted from the second diffraction position P2 is converted from the Y direction to the Z direction by the second polarization conversion element 22 (S-polarized light → P-polarized light). The reflection plane 12M reflects the second-wavelength combined beam CL2, whose polarization direction has been converted, in the +Z direction. The second-wavelength combined beam CL2 passes through the polarization plane 12R that transmits P-polarized light. Meanwhile, the first-wavelength combined beam CL1 is reflected by the polarization plane 12R, and the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 are coaxially combined to form a third-wavelength combined beam. The third-wavelength combined beam CL3 is collected by the collecting lens 50 and optically coupled to the optical fiber 60.

[0088] The configurations of the first optical member 10 and the second optical member 12 are not limited to the example in Fig. 5. The first optical member 10 and the second optical member 12 may have different configurations.

[0089] In this embodiment, the first diffraction element 40A and the second diffraction element 40B are included in separate diffraction gratings 40, but two different regions of the same diffraction grating 40 may function as the first diffraction element 40A and the second diffraction element 40B, respectively.

[0090] In this embodiment, multiple laser beams L can be incident parallel to the first optical member 10, which makes it possible to efficiently perform polarization separation of the laser beams L. Furthermore, since a single diffraction grating is placed on the optical path of each of the polarized beams (L1, L3), it is possible to reduce optical loss due to diffraction.

[0091] <Embodiment 3> 6 shows a configuration example of a wavelength beam combining device 130 according to another embodiment of the present disclosure. In this wavelength beam combining device 130, two diffraction gratings 40 are arranged such that the first wavelength combined beam CL1 and the second wavelength combined beam CL2 are parallel and face each other (arranged anti-parallel), and the first wavelength combined beam CL1 and the second wavelength combined beam CL2 are incident on the second optical member 12 from opposite directions.

[0092] 6 does not have a reflecting surface 10M. In the wavelength beam combining device 130, the positions and orientations of the multiple first mirrors 30A and the multiple second mirrors 30B are adjusted to widen the distance between the first diffraction position P1 and the second diffraction position P2, and the second optical member 12 is disposed between the first diffraction position P1 and the second diffraction position P2.

[0093] The configuration of the second optical member 12 in the wavelength beam combining device 130 is different from the configuration of the second optical member 12 in the wavelength beam combining device 120 in that the polarization plane 12R is perpendicular to the reflection surface 12M. In the wavelength beam combining device 130, the first wavelength combined beam CL1 and the second wavelength combined beam CL2 are incident on the second optical member 12 from the same direction so as to be parallel and face each other, and therefore the polarization plane 12R and the reflection surface 12M are arranged parallel to each other. The second optical member 12 can be fabricated by combining a cube-shaped polarizing beam splitter BS and a prism whose cross section is a right-angled isosceles triangle with their orientations changed.

[0094] In this embodiment, multiple laser beams L can be incident parallel to the first optical member 10, which makes it possible to efficiently perform polarization separation of the laser beams L. Furthermore, since a single diffraction grating is placed on the optical path of each of the polarized beams (L1, L3), it is possible to reduce optical loss due to diffraction.

[0095] In each of the above embodiments, the first optical member 10 includes a polarizing beam splitter BS (first polarizing beam splitter) that splits the multiple laser beams L into multiple first polarized beams L1 and multiple second polarized beams L2, and the second optical member 12 includes a polarizing beam splitter BS (second polarizing beam splitter) that combines the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2. However, as described above, the second optical member 12 does not need to include the polarizing beam splitter BS.

[0096] <Embodiment 4> 7 shows an exemplary configuration of a wavelength beam combining device 140 according to another embodiment of the present disclosure. The wavelength beam combining device 140 includes a single diffraction grating 42 including a first diffractive element 40A and a second diffractive element 40B. The diffraction grating 42 emits the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 in the same direction. The second optical member in this embodiment includes a lens 50 that receives and focuses the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2 emitted from the diffraction grating 42.

[0097] The first optical member 10 includes a polarizing beam splitter BS that splits the multiple laser beams L into multiple first polarized beams L1 and multiple second polarized beams L2. The first optical member 10 also has a reflecting surface 10M that reflects one of the multiple first polarized beams L1 and the multiple second polarized beams L2 split by the polarizing beam splitter BS. The reflecting surface 10M makes the traveling direction of the multiple first polarized beams L1 parallel to the traveling direction of the multiple second polarized beams L2.

[0098] The wavelength beam combining device 140 further includes a third optical member 18 that shifts the positions of the multiple first polarized beams L1 reflected by the reflecting surface 10M of the first optical member 10 in the Y direction. The third optical member 18 is, for example, a rhomboid prism. The function of the third optical member 18 will be described below.

[0099] FIG. 8 is a schematic diagram illustrating the function of the third optical member 18. The right side of FIG. 8 schematically illustrates the optical path of the laser beam L having a peak wavelength λ3 as viewed from the -Z direction. More specifically, the optical path of the first polarized beam L1 separated from the laser beam L having a peak wavelength λ3 by the first optical member 10 is shifted in the +Y direction by the third optical member 18. In the example of FIG. 8, the third optical member 18 is a rhomboid prism having a pair of parallel reflecting surfaces R1 and R2 at its end faces. A rhomboid prism has a prism shape in which the cross section parallel to the XY plane is a parallelogram. The third optical member 18 may also be two mirrors with parallel reflecting surfaces. On the other hand, the left side of FIG. 8 illustrates that the second polarized beam L2 separated from the laser beam L having a peak wavelength λ3 by the first optical member 10 and the third polarized beam L3 passing through the first polarization conversion element 20 travel in the +X direction without being shifted by the third optical member 18. Such a function of the third optical member 18 makes it possible to shift the first polarized beam L1 in the Y direction relative to the third polarized beam L3.

[0100] 7, the optical path of the first polarized beam L1 reflected by the multiple first mirrors 30A and the optical path of the third polarized beam L3 reflected by the multiple second mirrors 30B appear to overlap. However, in reality, the position of the optical path of the first polarized beam L1 reflected by the multiple first mirrors 30A is shifted in the +Y direction relative to the position of the optical path of the third polarized beam L3 reflected by the multiple second mirrors 30B.

[0101] The shift amount in the Y direction by the third optical member 18 is determined to be an amount that prevents the first mirrors 30A from interfering with the progression of the third polarized beam L3. In other words, this shift amount is larger than the size in the Y direction of each of the first mirrors 30A (for example, 5 mm to 20 mm).

[0102] 8, the reflecting surface R1 of the third optical member 18 reflects the first polarized beam L1 in the +Y direction, but the reflection direction of the first polarized beam L1 by the reflecting surface R1 may be rotated from the +Y direction by rotating the orientation of the reflecting surface R1 of the third optical member 18. The important point is to widen the distance in the Y direction between the optical path of the first polarized beam L1 and the third polarized beam L3. The multiple first mirrors 30A and multiple second mirrors 30B in FIG. 7 are arranged so that the first diffraction position P1 and the second diffraction position P2 are aligned in a direction parallel to the diffraction grooves of the diffraction grating 42.

[0103] The upper part of FIG. 8 schematically shows the positions of the first diffraction element 40A and the second diffraction element 40B on the diffraction grating 42. The diffraction grating 42 has diffraction grooves extending in the Y direction. As shown in FIG. 8, the first diffraction position P1 is located on the first diffraction element 40A, and the second diffraction position P2 is located on the second diffraction element 40B. According to this embodiment, different regions of a single diffraction grating 42 can be used as the first diffraction element 40A and the second diffraction element 40B. This allows the number of diffraction gratings to be reduced.

[0104] According to this embodiment, the first wavelength combined beam CL1 emitted from the first diffraction position P1 and the second wavelength combined beam CL2 emitted from the second diffraction position P2 are not strictly coaxial. Therefore, the first wavelength combined beam CL1 and the second wavelength combined beam CL2 are spatially combined by the condenser lens 50 of the second optical member 12 and enter the optical fiber 60. From the viewpoint of increasing the coupling efficiency of light to the optical fiber 60, it is preferable that the center-to-center distance between the first diffraction position P1 and the second diffraction position P2 on the diffraction grating 42 is short.

[0105] In this embodiment, the third optical element 18 shifts the optical path of the first polarized beam L1 in the Y direction, but the same effect can be achieved by shifting the optical path of the second polarized beam L2 or the third polarized beam L3 in the Y direction.

[0106] In this embodiment as well, multiple laser beams L can be incident parallel to the first optical member 10, thereby enabling efficient polarization separation of the laser beams L. Furthermore, since a single diffraction grating 42 is placed on the optical path of the polarized beams (L1, L3), optical loss due to diffraction can be reduced.

[0107] In this embodiment, the laser beam incident on the optical fiber 60 is not a polarization-combined beam of the first-wavelength combined beam CL1 and the second-wavelength combined beam CL2. Therefore, the laser beam incident on the optical fiber 60 is linearly polarized in a specific direction (Y direction). However, the polarization state of the laser beam incident on the optical fiber 60 may change during propagation through the optical fiber 60. Therefore, if the optical fiber 60 is sufficiently long, the polarization of the laser beam optically coupled to the input end face may be broken, and the laser beam may be in, for example, an unpolarized state at the output end face. This also applies to the embodiments described below.

[0108] <Embodiment 5> 9 shows a configuration example of a wavelength beam combining device 150 according to another embodiment of the present disclosure. Unlike the wavelength beam combining device 140 of FIG. 7, this wavelength beam combining device 150 does not include a third optical member 18 that shifts the optical path.

[0109] The right side of Fig. 10 schematically shows that the first polarized beam L1, which is separated by the first optical member 10 from the laser beam L having a peak wavelength λ3 as viewed from the -Z direction, travels in the +X direction after being reflected by the reflecting surface 10M. On the other hand, the left side of Fig. 10 schematically shows that the second polarized beam L2, which is separated by the first optical member 10 from the laser beam L having a peak wavelength λ3, and the third polarized beam L3, which has passed through the first polarization conversion element 20, travel in the +X direction.

[0110] 9, in this embodiment, the multiple first mirrors 30A are arranged so as not to interfere with the third polarized beam L3 reflected by the multiple second mirrors 30B. Furthermore, the multiple first mirrors 30A and the multiple second mirrors 30B are arranged so that the first diffraction position P1 and the second diffraction position P2 are aligned in a direction crossing the diffraction grooves of the diffraction grating 42.

[0111] The upper part of Fig. 10 schematically shows the positions of the first diffractive element 40A and the second diffractive element 40B on the diffraction grating 42. As in the previous embodiment, the diffraction grating 42 has diffraction grooves extending in the Y direction. As shown in Fig. 10, the first diffraction position P1 is on the first diffractive element 40A, and the second diffraction position P2 is on the second diffractive element 40B. The first diffractive element 40A and the second diffractive element 40B may overlap on the diffraction grating 42.

[0112] This embodiment also makes it possible to use different regions of a single diffraction grating 42 as the first diffraction element 40A and the second diffraction element 40B, thereby reducing the number of diffraction gratings.

[0113] In this embodiment, the first wavelength combined beam CL1 emitted from the first diffraction position P1 and the second wavelength combined beam CL2 emitted from the second diffraction position P2 are not strictly coaxial. Therefore, the first wavelength combined beam CL1 and the second wavelength combined beam CL2 are spatially combined by the condenser lens 50 of the second optical member 12 and enter the optical fiber 60. From the viewpoint of increasing the coupling efficiency of light to the optical fiber 60, it is preferable that the center-to-center distance between the first diffraction position P1 and the second diffraction position P2 on the diffraction grating 42 is short.

[0114] 9, there may be a significant difference between the angle at which the multiple first polarized beams L1, traveling from each of the multiple first mirrors 30A toward the first diffraction position P1, enter the diffraction grating 42 and the angle at which the multiple third polarized beams L3, traveling from each of the multiple second mirrors 30B toward the second diffraction position P2, enter the diffraction grating 42. By adjusting the positions and orientations of the multiple first mirrors 30A and the multiple second mirrors 30B, it is also possible to make a pair of beams having the same wavelength, the first polarized beams L1 and the third polarized beams L3, enter the diffraction grating 42 in parallel at the same angle. Meanwhile, it is preferable to minimize the difference between the diffraction angle of the first-wavelength combined beam CL1 traveling from the first diffraction position P1 toward the condenser lens 50 and the diffraction angle of the second-wavelength combined beam CL2 traveling from the second diffraction position P2 toward the condenser lens 50. Because the angle of incidence (αn) and the diffraction angle (β) satisfy the relationship of Equation (1), the first diffraction position P1 and the second diffraction position P2 cannot be made to coincide with each other. By increasing the distance from the multiple first mirrors 30A and multiple second mirrors 30B to the diffraction grating 42, it is possible to reduce the difference in the incident angle (αn) and shorten the center-to-center distance between the first diffraction position P1 and the second diffraction position P2.

[0115] In this embodiment as well, multiple laser beams L can be incident parallel to the first optical member 10, which makes it possible to efficiently perform polarization separation of the laser beams L. Furthermore, since a single diffraction grating is placed on the optical path of the polarized beams (L1, L3), it is possible to reduce optical loss due to diffraction.

[0116] [Direct diode laser device] Next, an example configuration of a DDL device according to an embodiment of the present disclosure will be described with reference to Fig. 11. Fig. 11 is a diagram schematically illustrating the configuration of a DDL device according to an exemplary embodiment of the present disclosure. The DDL device 1000 shown in Fig. 11 includes the wavelength beam combining device 100 shown in Fig. 1, a plurality of semiconductor laser devices 72 each emitting laser light corresponding to one of a plurality of laser beams L, and an optical fiber array device 70 configured to form the one of the plurality of laser beams L from the laser light emitted from each semiconductor laser device 72.

[0117] 11, the number of semiconductor laser devices 72 is three, but is not limited to this example. The number of semiconductor laser devices 72 is determined depending on the required optical output or irradiance. The wavelength of the laser light emitted from the semiconductor laser devices 72 can also be selected depending on the material to be processed.

[0118] The laser light emitted from each semiconductor laser device 72 is optically coupled to a corresponding optical fiber 74 of the optical fiber array device 70. The multiple semiconductor laser devices 72 are configured to oscillate at different peak wavelengths. Even if the laser light emitted from each semiconductor laser device 72 is linearly polarized, if the optical fiber 74 is not a polarization-maintaining fiber, the polarization state of the laser light changes while passing through the optical fiber 74. Therefore, the multiple laser beams L formed by the optical fiber array device 70 are unpolarized.

[0119] Examples of the semiconductor laser device 72 include an external cavity laser (ECL) device, a distributed feedback (DFB) laser device, and a distributed Bragg reflector (DBR) laser device.

[0120] The optical fiber array device 70 allows the optical fibers 74 to be aligned, making it easy to adjust the emission angle of the laser beam L. As a result, it becomes easy to emit multiple laser beams L in parallel with high precision from the optical fiber array device 70. The optical fibers extending from the semiconductor laser device 72 can also be fusion-spliced ​​to the optical fibers 74 of the optical fiber array device 70. The optical fiber array device 70 is equipped with a lens system that collimates the laser light emitted from the tip of each optical fiber 74.

[0121] In the DDL device 1000 according to this embodiment, even if the polarization state of the laser light emitted from the plurality of semiconductor laser devices 72 is made unpolarized by the optical fiber array device 70, the wavelength beam combining device 100 can form a wavelength combined beam CL3 from the plurality of unpolarized laser beams L.

[0122] The DDL device 1000 may include other wavelength beam combiners 110, 120, 130, 140, and 150 instead of the wavelength beam combiner 100.

[0123] [Laser processing machine] Next, an example configuration of a laser processing machine according to an embodiment of the present disclosure will be described with reference to Fig. 12. Fig. 12 is a diagram showing the configuration of a laser processing machine according to an exemplary embodiment of the present invention. A laser processing machine 2000 shown in Fig. 12 includes a light source device 1100, which is the DDL device 1000 shown in Fig. 11, an optical transmission fiber 90 extending from the light source device 1100 and coupled to a wavelength-combined beam CL3 emitted from the light source device 1100, and a processing head 1200 connected to the optical transmission fiber 90. The processing head 1200 irradiates an object 1300 with the wavelength-combined beam CL3 emitted from the optical transmission fiber 90.

[0124] 12, the number of light source devices 1100 is one, but is not limited to this example. The processing head 1200 may be connected to a plurality of light source devices 1100 via optical transmission fibers 90.

[0125] In the laser processing machine 2000 according to this embodiment, a high-power laser beam is generated by wavelength beam combining and is efficiently coupled to an optical fiber, making it possible to obtain a high-power density laser beam with excellent beam quality and high energy conversion efficiency.

[0126] The laser beam emitted from the processing head 1200 may include a laser beam other than the laser beam emitted from the semiconductor laser device 72 and combined as shown in Fig. 11. For example, the peak wavelength of the laser beam emitted from the semiconductor laser device 72 and combined as shown in Fig. 11 is in the wavelength range of 430 nm to 480 nm, but a laser beam having a peak wavelength of, for example, near-infrared may be superimposed. Depending on the material to be processed, a laser beam having a wavelength with a high light absorption rate of the material may be superimposed as appropriate.

[0127] The present disclosure includes a wavelength-combined beam device, a direct diode laser device, and a laser processing machine as described in the following items. [Item 1] A wavelength beam combining device that combines a plurality of laser beams having different peak wavelengths, a first optical member that separates the plurality of laser beams into a plurality of first polarized beams that are linearly polarized in a first polarization direction and a plurality of second polarized beams that are linearly polarized in a second polarization direction that is orthogonal to the first polarization direction; a first polarization conversion element that converts the plurality of second polarized beams into a plurality of third polarized beams that are linearly polarized in the first polarization direction; a plurality of first mirrors that reflect and direct each of the plurality of first polarized beams toward a first diffraction position; a plurality of second mirrors that reflect and direct each of the plurality of third polarized beams to a second diffraction position; a first diffractive element that receives the first polarized beams reflected by the first mirrors at the first diffraction position and diffracts the first polarized beams to form a first wavelength combined beam in which the first polarized beams are coaxially superimposed; a second diffraction element that receives the third polarized beams reflected by the second mirrors at the second diffraction position and diffracts the third polarized beams to form a second wavelength combined beam in which the third polarized beams are coaxially superimposed; a second optical member onto which the first wavelength combined beam and the second wavelength combined beam are incident; 1. A wavelength beam combining device comprising: [Item 2] a first diffraction grating including the first diffractive element; a second diffraction grating including the second diffraction element; a second polarization conversion element that changes the polarization state of at least one of the first wavelength combined beam and the second wavelength combined beam to make the polarization directions of the first wavelength combined beam and the second wavelength combined beam orthogonal to each other; Equipped with Item 1. The wavelength beam combining device according to item 1, wherein the second optical member forms and emits a third wavelength combined beam by coaxially superimposing the first wavelength combined beam and the second wavelength combined beam. [Item 3] Item 3. The wavelength beam combining device according to item 2, wherein each of the first diffraction grating and the second diffraction grating has diffraction grooves extending in the first polarization direction. [Item 4] the first optical member includes a first polarizing beam splitter that splits the plurality of laser beams into the plurality of first polarized beams and the plurality of second polarized beams; 4. The wavelength beam combining device according to any one of items 1 to 3, wherein the second optical element includes a second polarizing beam splitter that combines the first wavelength combined beam and the second wavelength combined beam. [Item 5] 4. The wavelength beam combining device according to any one of items 1 to 3, wherein the first diffraction grating and the second diffraction grating are arranged so that the first wavelength combined beam and the second wavelength combined beam are orthogonal to each other, and the first wavelength combined beam and the second wavelength combined beam are incident on the second optical member from directions orthogonal to each other. [Item 6] Item 3. The wavelength beam combining device of item 2, comprising a lens for focusing the third wavelength combined beam. [Item 7] Item 5. The wavelength beam combining device according to item 4, wherein the first optical element has a reflective surface that reflects one of the plurality of first polarized beams and the plurality of second polarized beams separated by the first polarizing beam splitter, and that makes the traveling direction of the plurality of first polarized beams parallel to the traveling direction of the plurality of second polarized beams. [Item 8] Item 8. The wavelength beam combining device according to item 7, wherein the first diffraction grating and the second diffraction grating are arranged to collimate the first wavelength combined beam and the second wavelength combined beam, and cause the first wavelength combined beam and the second wavelength combined beam to be incident on the second optical element from the same direction. [Item 9] Item 8. The wavelength beam combining device according to item 7, wherein the first diffraction grating and the second diffraction grating are arranged to make the first wavelength combined beam and the second wavelength combined beam anti-parallel to each other, and the first wavelength combined beam and the second wavelength combined beam are incident on the second optical member from directions opposite to each other. [Item 10] a single diffraction grating including the first diffractive element and the second diffractive element; the diffraction grating emits the first-wavelength combined beam and the second-wavelength combined beam in the same direction; Item 2. The wavelength beam combining device according to item 1, wherein the second optical member includes a lens that receives and focuses the first wavelength combined beam and the second wavelength combined beam emitted from the diffraction grating. [Item 11] the first optical member includes a polarizing beam splitter that splits the plurality of laser beams into the plurality of first polarized beams and the plurality of second polarized beams; and Item 11. The wavelength beam combining device according to item 10, wherein the first optical element has a reflective surface that reflects one of the plurality of first polarized beams and the plurality of second polarized beams separated by the polarizing beam splitter, and that makes the traveling direction of the plurality of first polarized beams parallel to the traveling direction of the plurality of second polarized beams. [Item 12] Item 12. The wavelength beam combining device according to item 11, wherein the diffraction grating has diffraction grooves extending in the first polarization direction. [Item 13] a third optical member (e.g., a rhomboid prism) that shifts the positions of the first polarized beams reflected by the reflecting surface of the first optical member in the first polarization direction; Item 13. The wavelength beam combining device according to item 12, wherein the plurality of first mirrors and the plurality of second mirrors are arranged so that the first diffraction positions and the second diffraction positions are aligned in a direction parallel to the diffraction grooves of the diffraction grating. [Item 14] Item 13. The wavelength beam combining device according to item 12, wherein the plurality of first mirrors and the plurality of second mirrors are arranged so that the first diffraction positions and the second diffraction positions are aligned in a direction crossing the diffraction grooves of the diffraction grating. [Item 15] A wavelength beam combining device according to any one of items 1 to 14, a laser light source that emits a plurality of laser beams in parallel; A direct diode laser device comprising: [Item 16] Item 16. The direct diode laser device according to item 15, wherein the laser light source comprises a plurality of semiconductor laser elements and a plurality of optical fibers respectively coupled to the plurality of semiconductor laser elements. [Item 17] At least one direct diode laser device according to item 15 or 16, an optical transmission fiber coupled to the laser beam emitted from the at least one direct diode laser device; a processing head connected to the optical transmission fiber; A laser processing machine comprising: [Industrial Applicability]

[0128] The wavelength beam combining device, direct diode laser device, and laser processing machine disclosed herein can be widely used in applications requiring high-output, high-power density laser light with high beam quality, such as cutting, drilling, localized heat treatment, surface treatment, metal welding, and 3D printing of various materials. [Explanation of symbols]

[0129] 10: First optical member 10M: Reflecting surface 10R: Polarizing surface 12: Second optical member 12M: Reflecting surface 12R: Polarizing surface 20: First polarization conversion element 30A: First mirror 30B: Second mirror 40: Diffraction grating 40A: First diffractive element 40B: Second diffractive element 42: Diffraction grating 50: Condenser lens 60: Optical fiber 70: Optical fiber array device 72: Semiconductor laser device 74: Optical fiber 90: Optical transmission fiber 100, 110, 120, 130, 140, 150: Wavelength beam combining device 1000: DDL device 1100: Light source device 1200: Processing head 1300: Object 2000: Laser processing machine BS: Polarizing beam splitter CL1: First wavelength combined beam CL2: Second wavelength combined beam CL3: Third wavelength combined beam L: Laser beam L1: First polarized beam L2: Second polarized beam L3: Third polarized beam P1: First diffraction position P2: Second diffraction position

Claims

1. A wavelength beam combining device that combines a plurality of laser beams having different peak wavelengths, a first optical member that separates the plurality of laser beams into a plurality of first polarized beams that are linearly polarized in a first polarization direction and a plurality of second polarized beams that are linearly polarized in a second polarization direction that is orthogonal to the first polarization direction; a first polarization conversion element that converts the plurality of second polarized beams into a plurality of third polarized beams that are linearly polarized in the first polarization direction; a plurality of first mirrors that reflect and direct each of the plurality of first polarized beams toward a first diffraction position; a plurality of second mirrors that reflect and direct each of the plurality of third polarized beams toward a second diffraction position; a first diffractive element that receives the first polarized beams reflected by the first mirrors at the first diffraction position and diffracts the first polarized beams to form a first wavelength combined beam in which the first polarized beams are coaxially superimposed; a second diffraction element that receives the third polarized beams reflected by the second mirrors at the second diffraction position and diffracts the third polarized beams to form a second wavelength combined beam in which the third polarized beams are coaxially superimposed; a second optical member onto which the first wavelength combined beam and the second wavelength combined beam are incident; 1. A wavelength beam combining device comprising:

2. a first diffraction grating including the first diffractive element; a second diffraction grating including the second diffraction element; a second polarization conversion element that changes the polarization state of at least one of the first wavelength combined beam and the second wavelength combined beam to make the polarization directions of the first wavelength combined beam and the second wavelength combined beam orthogonal to each other; Equipped with The wavelength beam combining device according to claim 1 , wherein the second optical member forms and emits a third wavelength combined beam by coaxially superimposing the first wavelength combined beam and the second wavelength combined beam.

3. 3. The wavelength beam combining device of claim 2, wherein the first diffraction grating and the second diffraction grating each have diffraction grooves extending in the first polarization direction.

4. the first optical member includes a first polarizing beam splitter that splits the plurality of laser beams into the plurality of first polarized beams and the plurality of second polarized beams; 4. The wavelength beam combining device of claim 3, wherein the second optical member includes a second polarizing beam splitter that combines the first wavelength combined beam and the second wavelength combined beam.

5. 5. The wavelength beam combining device of claim 4, wherein the first diffraction grating and the second diffraction grating are arranged to orthogonally intersect the first wavelength combined beam and the second wavelength combined beam, and the first wavelength combined beam and the second wavelength combined beam are incident on the second optical member from directions orthogonal to each other.

6. 3. The wavelength beam combining device of claim 2, further comprising a lens for focusing the third wavelength combined beam.

7. 5. The wavelength beam combining device of claim 4, wherein the first optical element has a reflective surface that reflects one of the plurality of first polarized beams and the plurality of second polarized beams separated by the first polarizing beam splitter, and that makes the propagation direction of the plurality of first polarized beams parallel to the propagation direction of the plurality of second polarized beams.

8. 8. The wavelength beam combining device of claim 7, wherein the first diffraction grating and the second diffraction grating are arranged to collimate the first wavelength combined beam and the second wavelength combined beam, and cause the first wavelength combined beam and the second wavelength combined beam to be incident on the second optical element from the same direction.

9. 8. The wavelength beam combining device of claim 7, wherein the first diffraction grating and the second diffraction grating are arranged to make the first wavelength combined beam and the second wavelength combined beam anti-parallel to each other, and cause the first wavelength combined beam and the second wavelength combined beam to be incident on the second optical member from directions opposite to each other.

10. a single diffraction grating including the first diffractive element and the second diffractive element; the diffraction grating emits the first-wavelength combined beam and the second-wavelength combined beam in the same direction; The wavelength beam combining device according to claim 1 , wherein the second optical member includes a lens that receives and focuses the first wavelength combined beam and the second wavelength combined beam output from the diffraction grating.

11. the first optical member includes a polarizing beam splitter that splits the plurality of laser beams into the plurality of first polarized beams and the plurality of second polarized beams; and The wavelength beam combining device of claim 10, wherein the first optical element has a reflective surface that reflects one of the plurality of first polarized beams and the plurality of second polarized beams separated by the polarizing beam splitter, and that makes the propagation direction of the plurality of first polarized beams parallel to the propagation direction of the plurality of second polarized beams.

12. 12. The wavelength beam combining device of claim 11, wherein the diffraction grating has diffraction grooves extending in the first polarization direction.

13. a third optical member that shifts positions of the plurality of first polarized beams reflected by the reflective surface of the first optical member in the first polarization direction, 13. The wavelength beam combining device of claim 12, wherein the plurality of first mirrors and the plurality of second mirrors are arranged so that the first diffraction positions and the second diffraction positions are aligned in a direction parallel to the diffraction grooves of the diffraction grating.

14. 13. The wavelength beam combining device of claim 12, wherein the plurality of first mirrors and the plurality of second mirrors are arranged so that the first diffraction positions and the second diffraction positions are aligned in a direction crossing the diffraction grooves of the diffraction grating.

15. A wavelength beam combining device according to any one of claims 1 to 14; a laser light source that emits a plurality of laser beams in parallel; A direct diode laser device comprising:

16. 16. The direct diode laser device according to claim 15, wherein the laser light source comprises a plurality of semiconductor laser elements and a plurality of optical fibers coupled to the plurality of semiconductor laser elements, respectively.

17. At least one direct diode laser device according to claim 15; an optical transmission fiber coupled to the laser beam emitted from the at least one direct diode laser device; a processing head connected to the optical transmission fiber; A laser processing machine comprising:

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