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

Abstract

It is desirable to reduce optical loss in a wavelength beam combining device.SOLUTION: A wavelength beam combining device that combines a plurality of laser beams having different peak wavelengths, the wavelength beam combining device including a diffraction grating that diffracts a plurality of first polarized beams linearly polarized in a first polarization direction and a plurality of second polarized beams linearly polarized in the first polarization direction, the first polarized beams and the second polarized beams being obtained from the plurality of laser beams, the plurality of first polarized beams and the plurality of second polarized beams are incident on an irradiation region of the diffraction grating so as to be mirror-symmetric with respect to a reference plane that includes a normal to the irradiation region and that is parallel to the first polarization direction, and the diffraction grating has a structure that is mirror-symmetric with respect to the reference plane in the irradiation region and superimposes the plurality of first polarized beams and the plurality of second polarized beams incident on the irradiation region in a direction parallel to the normal to form a wavelength-combined beam.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 process a wide variety of materials, including cutting, drilling, and marking, as well as to weld metal materials. Some of the carbon dioxide gas lasers and YAG solid-state lasers that have traditionally been used for such laser processing are being replaced by fiber lasers with high energy conversion efficiency. Laser diodes (hereafter simply referred to as LDs) are used as pump light sources for fiber laser devices. 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 describes a polarization splitting / combining device that aligns the polarization directions of light having mixed polarization directions and extracts the same. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent No. 6,192,062 [Patent Document 2] Japanese Patent Application Publication No. 08-152580 Summary of the Invention [Problem to be solved by the invention]

[0006] In a wavelength beam combiner that combines a plurality of laser beams having different peak wavelengths, it is desired to reduce optical loss within the device. [Means for solving the problem]

[0007] The wavelength beam combining device of the present disclosure is a wavelength beam combining device that combines multiple laser beams having different peak wavelengths, and in one embodiment, includes a diffraction grating that diffracts multiple first polarized beams linearly polarized in a first polarization direction obtained from the multiple laser beams and multiple second polarized beams linearly polarized in the first polarization direction, wherein the multiple first polarized beams and the multiple second polarized beams are incident on an irradiation area of ​​the diffraction grating in a mirror-symmetric manner with respect to a reference plane that is parallel to the first polarization direction and includes a normal to the irradiation area, and the diffraction grating has a structure that is mirror-symmetric with respect to the reference plane in the irradiation area, and the multiple first polarized beams and the multiple second polarized beams that are incident on the irradiation area are superimposed in a direction parallel to the normal to form a wavelength combined beam.

[0008] In one embodiment, a direct diode laser device according to the present disclosure includes the wavelength beam combining device described above and a plurality of semiconductor laser devices, each of which emits a laser beam corresponding to one of the plurality of laser beams.

[0009] In one embodiment, the laser processing machine of the present disclosure includes at least one direct diode laser device described above, an optical transmission fiber coupled to the wavelength-combined 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 embodiments of the present disclosure, optical losses within a wavelength beam combining device can be reduced. [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 diagram schematically illustrating an example of the configuration of a diffraction grating. [Figure 3] FIG. 3 is a diagram showing a schematic configuration of a modified example of the wavelength beam combining device. [Figure 4A] FIG. 4A is a side view schematically showing the configuration of a modified diffraction grating. [Figure 4B] FIG. 4B is another side view schematically showing the configuration of a modified diffraction grating. [Figure 4C] FIG. 4C is a top view schematically showing the configuration of a modified diffraction grating. [Figure 5] FIG. 5 is a diagram schematically showing the configuration of another modified diffraction grating. [Figure 6] FIG. 6 is a diagram schematically illustrating the configuration of a DDL device according to an exemplary embodiment of the present disclosure. [Figure 7] FIG. 7 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] First, with reference to FIG. 1, an exemplary configuration of a wavelength beam combining device according to an embodiment of the present disclosure will be described. FIG. 1 is a diagram schematically illustrating the configuration of a wavelength beam combining device according to an exemplary embodiment of the present disclosure. The wavelength beam combining device 100 illustrated in FIG. 1 combines multiple laser beams L having different peak wavelengths. The wavelength beam combining device 100 includes an optical element 10, a polarization conversion element 20, multiple first light reflecting members 30a, multiple second light reflecting members 30b, and a diffraction grating 40. The wavelength beam combining device 100 may further include a condenser lens 50 and an optical fiber 60. The optical element 10 in this embodiment is a polarizing beam splitter. Therefore, hereinafter, the optical element 10 will also be referred to as a polarizing beam splitter BS.

[0016] For reference, the accompanying drawings including FIG. 1 schematically show 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 when in use, and the orientation of the wavelength beam combining device 100 is arbitrary.

[0017] As will be explained in detail later, the wavelength beam combining device 100 according to this embodiment uses the polarizing beam splitter BS, the polarization conversion element 20, the plurality of first light reflecting members 30a, and the plurality of second light reflecting members 30b to obtain the following plurality of first polarized beams L1 and the plurality of second polarized beams L2, which are linearly polarized in the same specific direction, from the plurality of laser beams L. The plurality of first polarized beams L1 and the plurality of second polarized beams L2 are incident on the irradiation area A of the diffraction grating 40 in mirror symmetry with respect to the reference plane P. The reference plane P includes the normal to the irradiation area A and is parallel to the polarization directions of the first polarized beams L1 and the second polarized beams L2. The diffraction grating 40 coaxially superimposes the plurality of first polarized beams L1 and the plurality of second polarized beams L2 incident on the irradiation area A in a direction parallel to the normal to the irradiation area A to form a wavelength combined beam CL with high power and optical density.

[0018] If the polarization directions of the first polarized beam L1 and the second polarized beam L2 are different, one polarization direction must be converted by another polarization conversion element so that it is perpendicular to the other polarization direction, and then the first polarized beam L1 and the second polarized beam L2, whose polarization directions are perpendicular to each other, must be combined by another polarizing beam splitter.

[0019] In the wavelength beam combiner 100, the polarization directions of the first polarized beam L1 and the second polarized beam L2 are the same when forming the wavelength combined beam CL, so there is no need for the above-mentioned polarization combining. Therefore, there is no optical loss due to other polarization conversion elements, other polarization beam splitters, or other optical components for polarization combining. This makes it possible to reduce optical loss within the wavelength beam combiner 100.

[0020] The laser beam L and the components of the wavelength beam combining device 100 are described in detail below.

[0021] <Laser beam L> The peak wavelengths of the multiple laser beams L are different from one another and may be included in the following predetermined wavelength range, 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. The wavelength width of the predetermined wavelength range may be, for example, 50 nm or less. If the absolute value of the difference between the maximum and minimum peak wavelengths is, for example, 50 nm or less, optical components with wavelength-dependent optical properties, such as the polarizing beam splitter BS, polarization conversion element 20, and condenser lens 50, can be used for multiple light beams having different peak wavelengths, regardless of the wavelength. When 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.

[0022] FIG. 1 illustrates three laser beams L with different peak wavelengths λ1, λ2, and λ3. The number of laser beams L is not limited to this example, and may be two, four, or more. The greater the number of laser beams L, such as ten or more, the higher the output and optical density of the wavelength-combined beam CL obtained by combining multiple laser beams L. Narrowing the intervals between the peak wavelengths of the multiple laser beams L allows the number of laser beams L within a given wavelength range to be increased.

[0023] 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.

[0024] 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 2 The diameter of the light beam can be, for example, 1 mm to 30 mm.

[0025] In the present 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 traveling direction of a collimated light beam such as the laser beam L. These straight lines may be considered to represent light rays passing through the centers of the respective light beams.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] <Optical member 10 (polarizing beam splitter BS)> The polarizing beam splitter BS used as the optical element 10 has a polarization surface 12 that separates each incident laser beam L into light beams with different polarization states. The transmittance and reflectance of the polarization surface 12 vary depending on the polarization state of the laser beam L. The polarization surface 12 of the polarizing beam splitter BS selectively reflects a polarized component that is linearly polarized in a predetermined direction and transmits a polarized component that is linearly polarized in a direction perpendicular to the predetermined direction. The polarization surface 12 is provided with, for example, a dielectric multilayer film that has polarization dependency.

[0030] In the example shown in FIG. 1, the polarization plane 12 of the polarizing beam splitter BS is perpendicular to the XZ plane, and the normal to the polarization plane 12 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.

[0031] In the accompanying drawings, 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.

[0032] As shown in Figure 1, the polarization surface 12 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 surface 12 of the polarizing beam splitter BS splits each of the multiple laser beams L into multiple first polarized beams L1 that are S-polarized and multiple third polarized beams L3 that are P-polarized. In this way, each laser beam L is split into a corresponding first polarized beam L1 and third polarized beam L3.

[0033] When multiple laser beams L traveling in the +Z direction are incident on polarization plane 12 of polarizing beam splitter BS, multiple first polarized (S-polarized) beams L1 reflected by polarization plane 12 travel in the -X direction, and multiple third polarized (P-polarized) beams L3 transmitted through polarization plane 12 travel in the +Z direction. The traveling directions of these first polarized (S-polarized) beam L1 and third polarized (P-polarized) beam L3 may be changed by an optical member such as a mirror, for example.

[0034] Each laser beam L may be incident on the polarization plane 12 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 third polarized beam L3. In the wavelength beam combining device 100, multiple laser beams L may be incident on the polarizing beam splitter BS in a parallel state. In this case, by setting the incident angle of each laser beam L with respect to the polarization plane 12 to 45°, it is possible to avoid light loss due to low separation efficiency of the polarized beams.

[0035] 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 third polarized (P-polarized) beam L3. 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 third polarized (P-polarized) beam L3. 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 third polarized (P-polarized) beam L3. 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."

[0036] 1, the polarizing beam splitter BS is a cube-type polarizing beam splitter, but is not limited to this example. The polarizing beam splitter BS may be a plate-type or other type of polarizing beam splitter.

[0037] <Polarization conversion element 20> 1, the polarization conversion element 20 converts the multiple third polarized beams L3, which are P-polarized light, into multiple second polarized beams L2, which are S-polarized light. The multiple second polarized (S-polarized) beams L2 travel in the +Z direction.

[0038] The polarization conversion element 20 may be, for example, 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.

[0039] In this way, the polarizing beam splitter BS and the polarization conversion element 20 can obtain a plurality of first polarized beams L1 and a plurality of second polarized beams L2 that are linearly polarized in a specific direction from, for example, a plurality of laser beams L that are generally unpolarized. 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 second polarized (S-polarized) beams L2.

[0040] 1, polarization surface 12 of polarizing beam splitter BS may reflect the P-polarized component of each laser beam L and transmit the S-polarized component. In this case, the multiple third polarized (P-polarized) beams L3 reflected by polarization surface 12 of polarizing beam splitter BS travel in the −X direction, and the multiple first polarized (S-polarized) beams L1 transmitted through polarization surface 12 of polarizing beam splitter BS travel in the +Z direction. Polarization conversion element 20 is disposed at a position where the multiple third polarized (P-polarized) beams L3 pass through, and converts the multiple third polarized (P-polarized) beams L3 into multiple second polarized (S-polarized) beams L2.

[0041] The phase difference formed by the half-wave plate depends on the wavelength of the incident light. Therefore, when three third polarized beams L3 with peak wavelengths of 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 second polarized beams L2 output from the polarization conversion element 20, and strictly speaking, elliptically polarized light may be included.

[0042] However, if all of the peak wavelengths λn are within a relatively narrow range, for example, 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.

[0043] <First Light Reflecting Member 30a and Second Light Reflecting Member 30b> As shown in FIG. 1, the multiple first light reflecting members 30a each reflect the multiple first polarized beams L1 and make them incident on a predetermined irradiation area A on the diffraction grating 40. The multiple first light reflecting members 30a correspond one-to-one to the multiple first polarized beams L1. The irradiation area A is a part of the area on the diffraction grating 40 where the grating structure is provided, and is located, for example, at the center of the surface of the diffraction grating 40. By adjusting the position and orientation of each of the multiple first light reflecting members 30a, the multiple first polarized beams L1 can be directed to the same position on the diffraction grating 40, i.e., the irradiation area A.

[0044] Similarly, the second light reflecting members 30b each reflect the second polarized beams L2 and cause them to be incident on a predetermined irradiation area A on the diffraction grating 40. The second light reflecting members 30b correspond one-to-one to the second polarized beams L2. By adjusting the position and orientation of each of the second light reflecting members 30b, the second polarized beams L2 can be directed toward the irradiation area A on the diffraction grating 40.

[0045] The plurality of first polarized beams L1 and the plurality of second polarized beams L2 reflected as described above travel parallel to the XZ plane and are incident on the illumination area A in mirror symmetry with respect to the reference plane P.

[0046] The first light reflecting member 30a and the second light reflecting member 30b may be formed, for example, from a dielectric multilayer film with low optical loss. A dielectric multilayer film has nearly 100% reflectance in a wavelength range called the stop band. As long as all of the peak wavelengths λn are included in the stop band, the first light reflecting members 30a and the second light reflecting members 30b may be formed from the same dielectric multilayer film. If optical loss is not a consideration, the first light reflecting members 30a and the second light reflecting members 30b may be formed from a metal material. The light reflecting surfaces of the light reflecting members 30a and 30b may, for example, include a circle with a diameter of 1 mm and be included in a circle with a diameter of 30 mm.

[0047] <Diffraction Grating 40> 1, the diffraction grating 40 diffracts a plurality of first polarized beams L1 and a plurality of second polarized beams L2 that are incident on the illumination area A in mirror symmetry with respect to the reference plane P. As a result, the diffraction grating 40 forms a wavelength-combined beam CL by coaxially superimposing the plurality of first polarized beams L1 and the plurality of second polarized beams L2 in a direction parallel to the normal to the illumination area A. The wavelength-combined beam CL is S-polarized, just like the first polarized beam L1 and the second polarized beam L2.

[0048] Due to misalignment occurring at the time of incidence, the multiple first polarized beams L1 and the multiple second polarized beams L2 may not be strictly mirror symmetric with respect to the reference plane P. Even in this case, the misalignment occurring at the time of incidence is permissible as long as the following first and second spots partially overlap. The first spot is a spot formed by the multiple first polarized beams L1 in the region of the diffraction grating 40 where the grating structure is provided. The second spot is a spot formed by the multiple second polarized beams L2 in the region of the diffraction grating 40 where the grating structure is provided. The first spot has a maximum intensity of 1 / e 2 The second spot is an area having an intensity 1 / e times or more of the maximum intensity of the second polarized beams L2. 2 The region where the grating structure of the diffraction grating 40 is provided may, for example, include a circle with a diameter of 1 mm and may be included in a circle with a diameter of 30 mm. The diameter of each of the first and second spots may, for example, be 1 mm or more and 30 mm or less.

[0049] Fig. 2 is a diagram schematically illustrating an example configuration of the diffraction grating 40. Fig. 2 also illustrates how the multiple first polarized beams L1 and the multiple second polarized beams L2 are diffracted. The diffraction grating 40 is a reflective diffraction grating.

[0050] As shown in FIG. 2, the diffraction grating 40 includes a diffraction section 40a having multiple diffraction grooves parallel to the Y direction, which is the first polarization direction, a dielectric multilayer film 40b supporting the diffraction section 40a, and a substrate 40c supporting the dielectric multilayer film 40b. The dielectric multilayer film 40b reflects the light beam passing through the diffraction section 40a, so that the diffraction grating 40 generates reflected diffracted light but does not generate transmitted diffracted light. The diffraction section 40a and the substrate 40c may be made of a light-transmitting material such as glass. The multiple diffraction grooves may be filled with another material, however, the refractive index of the other material may differ from that of the diffraction section 40a.

[0051] As shown in FIG. 2, the diffraction grating 40 has a mirror-symmetric structure with respect to the reference plane P in the irradiation area A. The diffraction grating 40 may be, for example, a so-called lamina-type diffraction grating, in which a plurality of rectangular grooves are formed on a flat surface. Because the diffraction grating 40 has such a mirror-symmetric structure, the diffraction efficiency of the plurality of first polarized beams L1 and the diffraction efficiency of the plurality of second polarized beams L2 are the same. Therefore, the diffraction efficiencies of both beams can be designed to be equally high. Even if the diffraction grating 40 does not have a strictly mirror-symmetric structure, it is acceptable as long as the absolute value of the difference in diffraction efficiency between the first and second polarized beams L1 and L2 is 5% or less.

[0052] Diffraction grating 40 diffracts the light beam that travels parallel to the XZ plane and enters illumination area A in a direction parallel to the XZ plane. Taking the normal to illumination area A as a reference, the incident angle of the light beam having a peak wavelength λn is αn and the diffraction angle is β, and the following equation (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 lines / mm or more and 5000 lines / mm or less.

[0053] In the example shown in Figure 2, the first-order diffracted light of the light beam incident on irradiation area A is reflected and diffracted in a direction parallel to the normal to irradiation area A, so m = 1 and β = 0°. The longer the peak wavelength λn, the larger the angle of incidence αn, so the relationship α1 < α2 < α3 holds, as shown in Figure 2. For example, when the grating pitch is 600 nm, N = 1667, and λ1 = 460 nm, λ2 = 465 nm, and λ3 = 470 nm, the relationships α1 = 50.05°, α2 = 50.80°, and α3 = 51.56°.

[0054] 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 same direction at the same diffraction angle β = 0°. The same is true for multiple second polarized beams L2 with different peak wavelengths λn. As a result, as shown in Figure 2, the multiple first polarized beams L1 and multiple second polarized beams L2 are coaxially superimposed as reflected diffracted light in a direction parallel to the normal to the irradiation area A, forming a wavelength-combined beam CL with high power and optical density.

[0055] In forming the wavelength combined beam CL, there is no need to polarization combine the first polarized beam L1 and the second polarized beam L2, so there is no light loss due to optical components for polarization combination, such as other polarization conversion elements and other polarizing beam splitters. As a result, it is possible to reduce light loss within the wavelength beam combiner 100. Because there are no optical components for polarization combination, the number of components in the wavelength beam combiner 100 can be reduced, and the configuration of the wavelength beam combiner 100 can be simplified.

[0056] A first polarized beam L1 and a second polarized beam L2, which are S-polarized light, are incident on an irradiation area A of 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 first polarized beam L1 and the second polarized beam L2, which are S-polarized light.

[0057] The diffraction grating 40 may generate zeroth-order reflective diffracted light, which is specularly reflected light, for at least one of the multiple first polarized beams L1. This zeroth-order reflective diffracted light travels along the optical path of the corresponding second polarized beam L2 in the opposite direction to the traveling direction of the second polarized beam L2 and may reach the output position of the laser beam L or its vicinity. When the laser beam L is output from an optical fiber, this zeroth-order reflective diffracted light may enter a portion of the optical fiber other than the core and damage the optical fiber. Similarly, the diffraction grating 40 may generate zeroth-order reflective diffracted light for at least one of the multiple second polarized beams L2, causing a similar phenomenon. When each first polarized beam L1 is incident on the irradiation area A at an incident angle of 0° to 44° or 46° to 90°, and each second polarized beam L2 is incident on the irradiation area A at an incident angle of 0° to 44° or 46° to 90°, the generation of the zeroth-order reflective diffracted light can be reduced.

[0058] The diffraction grating 40 can be designed to most easily produce the reflected diffracted light that forms the wavelength combined beam CL, but other reflected diffracted light may also be produced by the diffraction grating 40. The wavelength beam combining device 100 may include, inside a housing that houses its components, a light absorbing member that absorbs reflected diffracted light other than the reflected diffracted light that forms the wavelength combined beam CL to prevent the other reflected diffracted light from becoming stray light.

[0059] In the example shown in Fig. 2, the reflective diffraction grating 40 includes a dielectric multilayer film 40b, but is not limited to this example. The reflective diffraction grating 40 may include a metal film provided on the surface of the multiple diffraction grooves of the diffractive section 40a, rather than the dielectric multilayer film 40b. A metal film can also reflect a light beam. The substrate 40c may be omitted.

[0060] When the laser beam L has a spectral width Δλn approximately centered on 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 give a width to the wavelength-combined beam CL 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, a wavelength-combined beam CL containing multiple peak wavelengths in a predetermined wavelength range can be formed, and its output and optical density can be effectively increased.

[0061] <Condenser lens 50 and optical fiber 60> As shown in FIG. 1 , the condenser lens 50 is disposed at a position where it receives the wavelength-combined beam CL, and condenses the wavelength-combined beam CL and inputs it into the optical fiber 60. The condenser lens 50 and the optical fiber 60 are located on the side of the diffraction grating 40 where the first polarized beam L1 and the second polarized beam L2 are incident. When viewed from the Y direction parallel to the first polarization direction, the condenser lens 50 and the optical fiber 60 are surrounded by the optical paths of the first polarized beam L1 and the second polarized beam L2 and are located inside these optical paths. This helps to reduce the size of the wavelength beam combining device 100 in two-dimensional directions parallel to the XZ plane.

[0062] The optical axis of the condenser lens 50 is parallel to the traveling direction of the wavelength-combined beam CL. The focal point of the condenser lens 50 is located at the incident end face 62 of the optical fiber 60. The condenser lens 50 may be a single lens or a combination of multiple lenses.

[0063] The optical fiber 60 emits the wavelength-combined beam CL incident on the incident end face 62 from the exit end face 64. The polarization state of the wavelength-combined beam CL may change during its passage through the optical fiber 60. Therefore, even if the wavelength-combined beam CL is S-polarized at the incident end face 62, it may be unpolarized at the exit end face 64, for example. The optical fiber 60 can have any length and be bent, so the wavelength-combined beam CL can be emitted in any direction from the exit end face 64 of the optical fiber 60, enabling the wavelength-combined beam CL to be extracted outside the wavelength beam combiner 100. When the optical fiber 60 extends so as to cross over or pass under the optical path of the first polarized beam L1 or the second polarized beam L2, the optical fiber 60 has a portion that overlaps with the optical path of the first polarized beam L1 or the second polarized beam L2 when viewed from the Y direction parallel to the first polarization direction. This contributes to the miniaturization of the wavelength beam combiner 100 in the Y direction.

[0064] As described above, in the wavelength beam combining device 100 according to this embodiment, the multiple first polarized beams L1 and the multiple second polarized beams L2, which are linearly polarized in the same specific direction and obtained from the multiple laser beams L, are incident on the irradiation area A of the diffraction grating 40 in mirror symmetry with respect to the reference plane P. As a result, the multiple first polarized beams L1 and the multiple second polarized beams L2 can be coaxially combined in a direction parallel to the normal to the irradiation area A as a wavelength combined beam CL having high output and optical density without polarization combining.

[0065] In the wavelength beam combiner 100, there is no need to polarization combine the first polarized beam L1 and the second polarized beam L2, so no optical loss occurs due to the optical components for polarization combining. Therefore, it is possible to reduce optical loss within the wavelength beam combiner 100. However, since the coaxially superimposed wavelength combined beam CL has a single polarization direction, it is possible to increase the optical output and brightness by polarization combining with another wavelength combined beam having a single polarization direction perpendicular to the polarization direction.

[0066] In the wavelength beam combining device 100 according to this embodiment, optical components other than the polarizing beam splitter BS and the polarization conversion element 20 may be used as long as a plurality of first polarized beams L1 and a plurality of second polarized beams L2 that are linearly polarized in the same specific direction can be obtained from a plurality of laser beams L. Optical components other than the plurality of first light reflecting members 30a and the plurality of second light reflecting members 30b may be used as long as the plurality of first polarized beams L1 and the plurality of second polarized beams L2 can be incident on the irradiation area A of the diffraction grating 40 in mirror symmetry with respect to the reference plane P. Optical components other than the condenser lens 50 and the optical fiber 60 may be used as long as the wavelength combined beam CL can be extracted outside the wavelength beam combining device 100.

[0067] [Modification of Wavelength Beam Combining Device 100] Next, a modified example of the wavelength beam combining device 100 will be described with reference to Fig. 3. Fig. 3 is a diagram schematically showing the configuration of a modified example of the wavelength beam combining device 100. The wavelength beam combining device 110 shown in Fig. 3 differs from the wavelength beam combining device 100 shown in Fig. 1 in the arrangement of the laser beams L with peak wavelengths λ1, λ2, and λ3 (λ1<λ2<λ3) and the arrangement of the multiple first light reflecting members 30a and the multiple second light reflecting members 30b.

[0068] In the wavelength beam combining device 100 shown in Fig. 1, the laser beam L having the shortest peak wavelength λ1 is located on the lower side (-X direction) of the diagram, and the laser beam L having the longest peak wavelength λ3 is located on the upper side (+X direction) of the diagram. In contrast, in the wavelength beam combining device 110 shown in Fig. 3, the laser beam L having the longest peak wavelength λ3 is located on the lower side (-X direction) of the diagram, and the laser beam L having the shortest peak wavelength λ1 is located on the upper side (+X direction) of the diagram.

[0069] The arrangement of the plurality of first light reflecting members 30a and the plurality of second light reflecting members 30b also differs depending on the arrangement of the plurality of laser beams L. As a result, the relationship α1<α2<α3 holds for the angle of incidence αn when the plurality of first polarized beams L1 are incident on the irradiation area A of the diffraction grating 40 and the angle of incidence αn when the plurality of second polarized beams L2 are incident on the irradiation area A of the diffraction grating 40.

[0070] Therefore, similar to the wavelength beam combining device 100, the wavelength beam combining device 110 can also coaxially combine a plurality of first polarized beams L1 and a plurality of second polarized beams L2 into a wavelength combined beam CL.

[0071] Furthermore, the wavelength beam combining device 110 can uniformly adjust the optical path lengths of the polarized beams having wavelengths λ1, λ2, and λ3. This makes it possible to uniformly adjust the spot diameters of the polarized beams in the irradiation area A, thereby improving the efficiency with which the polarized beams are coupled into the optical fiber 60 by the condenser lens 50.

[0072] [Modification of Diffraction Grating 40] 2, an irradiation area A on the diffraction grating 40 is irradiated with the first polarized beam L1 and the second polarized beam L2. In this case, the first polarized beam L1 and the second polarized beam L2 are incident on the same portion of the dielectric multilayer film 40b located directly below the irradiation area A, which may result in localized heating of this portion and damage to the diffraction grating 40. The dielectric multilayer film 40b is made of a light-transmitting material that does not easily absorb light, but when the first polarized beam L1 and the second polarized beam L2 are incident on the same portion of the dielectric multilayer film 40b, this portion may be locally heated.

[0073] 4A to 4C, a reflective diffraction grating that is less susceptible to the above damage will be described below as a modification of diffraction grating 40. The reflective diffraction grating in this modification has a cooling structure.

[0074] 4A to 4C are a side view, another side view, and a top view, respectively, that schematically show the configuration of a modified example of diffraction grating 40. The hatched circle in FIG. 4C represents irradiation area A. Diffraction grating 40-1 shown in FIGS. 4A to 4C differs from diffraction grating 40 shown in FIG. 2 in that substrate 40c has one or more cooling paths 40c1 for flowing cooling water as a cooling structure.

[0075] The above-described cooling structure allows heat generated in the portion of the dielectric multilayer film 40b where the first polarized beam L1 and the second polarized beam L2 are concentrated to be released to the outside of the diffraction grating 40 via the cooling path 40c1, thereby making it possible to cool the heated portion.

[0076] 4A to 4C, when viewed from a direction parallel to the normal to the irradiation area A, the irradiation area A is located between two cooling paths 40c1. The two cooling paths 40c1 extend in a direction parallel to the irradiation area A and perpendicular to the direction in which the diffraction grooves extend. The two cooling paths 40c1 are located in mirror symmetry with respect to a plane perpendicular to the irradiation area A and dividing the irradiation area A into two equal parts. This configuration makes it easier to uniformly cool the portion of the dielectric multilayer film 40b where the first polarized beam L1 and the second polarized beam L2 are concentrated.

[0077] 4A to 4C, the number of cooling paths 40c1 may be one, or three or more. There are no restrictions on the positional relationship between irradiation area A and cooling path 40c1 when viewed from a direction parallel to the normal to irradiation area A, but it is preferable to arrange cooling path 40c1 so that it does not overlap irradiation area A when viewed from a direction parallel to the normal to irradiation area A. This is because it reduces the possibility of heat generated in the area where the first polarized beam L1 and the second polarized beam L2 are concentrated being excessively transmitted to cooling path 40c1 and damaging cooling path 40c1.

[0078] If the diffraction grating 40-1 does not include the dielectric multilayer film 40b but includes a metal film provided on the surface of the diffraction grooves of the diffractive section 40a, the metal film is more likely to be damaged by heating caused by irradiation with the first polarized beam L1 and the second polarized beam L2 than the dielectric multilayer film 40b. Therefore, in this case, providing the cooling structure described above is more effective.

[0079] Next, referring to FIG. 5, a transmission-type diffraction grating will be described as another variation of the diffraction grating 40. FIG. 5 is a diagram schematically illustrating the configuration of another variation of the diffraction grating 40. FIG. 5 also illustrates a condenser lens 50 and an optical fiber 60. The diffraction grating 40-2 shown in FIG. 5 is a transmission-type diffraction grating having a plurality of grooves parallel to the Y direction, and has a mirror-symmetric structure with respect to the reference plane P in the irradiation area A. The diffraction grating 40-2 coaxially superimposes a plurality of first polarized beams L1 and a plurality of second polarized beams L2 as transmitted diffracted light in a direction parallel to the normal to the irradiation area A to form a wavelength-combined beam CL.

[0080] The condenser lens 50 is disposed at a position where it receives the wavelength-combined beam CL, and condenses the wavelength-combined beam CL and inputs it into the optical fiber 60. Therefore, the condenser lens 50 and the optical fiber 60 are located on the opposite side of the diffraction grating 40-2 from the side onto which the first polarized beam L1 and the second polarized beam L2 are incident.

[0081] The diffraction grating 40-2 can be designed to most easily produce the transmitted diffracted light that forms the wavelength combined beam CL, but the diffraction grating 40-2 may also produce other transmitted diffracted light and may also produce reflected diffracted light. The wavelength beam combining device 100 may include, inside a housing that houses its components, a light absorbing member that absorbs diffracted light other than the transmitted diffracted light that forms the wavelength combined beam CL to prevent the diffracted light from becoming stray light.

[0082] Alternatively, the diffraction grating 40-2 may coaxially superimpose the multiple first polarized beams L1 and the multiple second polarized beams L2 as reflected diffracted light rather than transmitted diffracted light to form the wavelength combined beam CL. In this case, the diffraction grating 40-2 can be designed to most easily produce the reflected diffracted light that forms the wavelength combined beam CL, but the diffraction grating 40-2 may also produce other reflected diffracted light and may also produce transmitted diffracted light. The wavelength beam combining device 100 may include a light absorbing member inside a housing that houses its components to absorb diffracted light other than the reflected diffracted light that forms the wavelength combined beam CL so that it does not become stray light.

[0083] When the diffraction grating 40-2 is used to form the wavelength-combined beam CL using transmitted diffracted light or reflected diffracted light, the diffraction grating 40-2 may be arranged upside down so that the multiple diffraction grooves face toward the focusing lens 50, unlike the example shown in Figure 5.

[0084] [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. 6. FIG. 6 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. 6 includes the wavelength beam combining device 100 shown in FIG. 1 and a plurality of semiconductor laser devices 72, each of which emits laser light corresponding to one of a plurality of laser beams L. The DDL device 1000 further includes an optical fiber array device 70 configured to form one of the plurality of laser beams L from the laser light emitted from each semiconductor laser device 72. The wavelength beam combining device 110 shown in FIG. 3 may be used instead of the wavelength beam combining device 100 shown in FIG. 1.

[0085] 6, 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] In the DDL device 1000 according to this embodiment, even if the polarization state of the laser light emitted from the multiple 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 CL from the multiple unpolarized laser beams L.

[0090] [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. 7. FIG. 7 is a diagram showing the configuration of a laser processing machine according to an exemplary embodiment of the present invention. The laser processing machine 2000 shown in FIG. 7 includes a light source device 1100, an optical transmission fiber 80 extending from the light source device 1100 and coupled to the wavelength-combined beam CL emitted from the light source device 1100, and a processing head 1200 connected to the optical transmission fiber 80. The processing head 1200 irradiates an object 1300 with the wavelength-combined beam CL emitted from the optical transmission fiber 80. The light source device 1100 is the DDL device 1000 shown in FIG. 6.

[0091] 7, 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 the optical transmission fiber 80.

[0092] 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-light-density laser beam with excellent beam quality and high energy conversion efficiency.

[0093] 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. 6. For example, the peak wavelength of the laser beam emitted from the semiconductor laser device 72 and combined as a wavelength is in the wavelength range of 430 nm to 480 nm, but in addition to that, for example, a laser beam having a peak wavelength in the near-infrared region 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.

[0094] 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.

[0095] [Item 1] A wavelength beam combining device that combines a plurality of laser beams having different peak wavelengths, a diffraction grating that diffracts a plurality of first polarized beams linearly polarized in a first polarization direction obtained from the plurality of laser beams and a plurality of second polarized beams linearly polarized in the first polarization direction, the plurality of first polarized beams and the plurality of second polarized beams are incident on an irradiation area of ​​the diffraction grating in a mirror symmetry manner with respect to a reference plane that includes a normal to the irradiation area and is parallel to the first polarization direction, The diffraction grating has a structure that is mirror-symmetric with respect to the reference plane in the irradiation area, and forms a wavelength-combined beam by superimposing the multiple first polarized beams and the multiple second polarized beams that are incident on the irradiation area in a direction parallel to the normal.

[0096] [Item 2] an optical member that separates the plurality of laser beams into the plurality of first polarized beams that are linearly polarized in the first polarization direction and a plurality of third polarized beams that are linearly polarized in a second polarization direction orthogonal to the first polarization direction; a polarization conversion element that converts the plurality of third polarized beams into the plurality of second polarized beams that are linearly polarized in the first polarization direction; Item 1. A wavelength beam combining device according to item 1, comprising:

[0097] [Item 3] a plurality of first light reflecting members that reflect the plurality of first polarized beams and cause them to be incident on the irradiation area of ​​the diffraction grating; a plurality of second light reflecting members that reflect the plurality of second polarized beams, respectively, to make them incident on the irradiation area of ​​the diffraction grating; Item 3. The wavelength beam combining device according to item 1 or 2, further comprising:

[0098] [Item 4] 4. The wavelength beam combining device according to any one of items 1 to 3, wherein the diffraction grating is a lamina type diffraction grating.

[0099] [Item 5] 5. The wavelength beam combining device according to any one of items 1 to 4, wherein the diffraction grating has a plurality of diffraction grooves parallel to the first polarization direction.

[0100] [Item 6] each of the plurality of first polarized beams is incident on the illumination area at an incident angle of 0° or more and 44° or less, or 46° or more and 90° or less; 6. The wavelength beam combining device of any one of items 1 to 5, wherein each of the plurality of second polarized beams is incident on the illumination area at an incident angle of 0° to 44° or 46° to 90°.

[0101] [Item 7] the optical member has a polarization surface that separates the plurality of laser beams into the plurality of first polarized beams and the plurality of third polarized beams; 7. The wavelength beam combining device according to claim 2, wherein each of the plurality of laser beams is incident on the polarization plane at an incident angle of 40° or more and 50° or less.

[0102] [Item 8] 8. The wavelength beam combining device according to any one of items 1 to 7, wherein the diffraction grating is a reflective diffraction grating and has a cooling structure.

[0103] [Item 9] the cooling structure is one or more cooling paths; Item 9. The wavelength beam combining device of item 8, wherein the one or more cooling paths do not overlap the illumination area when viewed in a direction parallel to the normal to the illumination area.

[0104] [Item 10] 10. The wavelength beam combining device according to any one of items 1 to 9, wherein each of the plurality of laser beams is emitted from a semiconductor laser device via an optical fiber.

[0105] [Item 11] Further comprising a condenser lens and an optical fiber; 11. The wavelength beam combining device according to any one of items 1 to 10, wherein the focusing lens focuses the wavelength combined beam and inputs it into the optical fiber.

[0106] [Item 12] Item 12. The wavelength beam combining device of item 11, wherein, when viewed in a direction parallel to the first polarization direction, the focusing lens and the optical fiber are surrounded by the optical paths of the plurality of first polarized beams and the optical paths of the plurality of second polarized beams.

[0107] [Item 13] Item 12. The wavelength beam combining device of item 11, wherein, when viewed in a direction parallel to the first polarization direction, the optical fiber has a portion that overlaps with the optical paths of the plurality of first polarized beams or the optical paths of the plurality of second polarized beams.

[0108] [Item 14] A wavelength beam combining device according to any one of items 1 to 13, a plurality of semiconductor laser devices, each of which emits a laser beam corresponding to one of the plurality of laser beams; A direct diode laser device comprising:

[0109] [Item 15] Item 15. The direct diode laser device of item 14, further comprising an optical fiber array device configured to form one of the plurality of laser beams from the laser light emitted from each of the plurality of semiconductor laser devices.

[0110] [Item 16] At least one direct diode laser device according to item 14 or 15, an optical transmission fiber coupled to the wavelength-combined 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]

[0111] The wavelength beam combining device, direct diode laser device, and laser processing machine of the present disclosure can be widely used in applications requiring high-power, high-light-density laser light with high beam quality, such as cutting various materials, drilling, localized heat treatment, surface treatment, metal welding, and 3D printing. [Explanation of symbols]

[0112] 10: Optical member 12: Polarization surface 20: Polarization conversion element 30a: First light reflecting member 30b: Second light reflecting member 40, 40-1, 40-2: Diffraction grating 40a: Diffraction section 40b: Dielectric multilayer film 40c: Substrate 40c1: Cooling path 50: Condenser lens 60: Optical fiber 62: Incident end face 64: Exit end face 70: Optical fiber array device 72: Semiconductor laser device 74: Optical fiber 80: Optical transmission fiber 100, 110: Wavelength beam combining device 1000: DDL device 1100: Light source device 1200: Processing head 1300: Object 2000: Laser processing machine BS: Polarizing beam splitter L: Laser beam L1: First polarized beam L2: Second polarized beam L3: Third polarized beam CL: Wavelength combined beam A: Irradiation area P: Reference plane

Claims

1. A wavelength beam combining device that combines a plurality of laser beams having different peak wavelengths, a diffraction grating that diffracts a plurality of first polarized beams linearly polarized in a first polarization direction obtained from the plurality of laser beams and a plurality of second polarized beams linearly polarized in the first polarization direction, the plurality of first polarized beams and the plurality of second polarized beams are incident on an irradiation area of ​​the diffraction grating in a mirror symmetry manner with respect to a reference plane that includes a normal to the irradiation area and is parallel to the first polarization direction, The diffraction grating has a structure that is mirror-symmetric with respect to the reference plane in the irradiation area, and forms a wavelength-combined beam by superimposing the plurality of first polarized beams and the plurality of second polarized beams that are incident on the irradiation area in a direction parallel to the normal.

2. an optical member that separates the plurality of laser beams into the plurality of first polarized beams that are linearly polarized in the first polarization direction and a plurality of third polarized beams that are linearly polarized in a second polarization direction orthogonal to the first polarization direction; a polarization conversion element that converts the plurality of third polarized beams into the plurality of second polarized beams that are linearly polarized in the first polarization direction; 10. The wavelength beam combining device of claim 1, comprising:

3. a plurality of first light reflecting members that reflect the plurality of first polarized beams, respectively, to make the beams incident on the irradiation areas of the diffraction grating; a plurality of second light reflecting members that reflect the plurality of second polarized beams, respectively, to make them incident on the irradiation areas of the diffraction grating; 3. The wavelength beam combining device of claim 1 or 2, further comprising:

4. 3. The wavelength beam combining device according to claim 1, wherein the diffraction grating is a lamina type diffraction grating.

5. 3. The wavelength beam combining device according to claim 1, wherein the diffraction grating has a plurality of diffraction grooves parallel to the first polarization direction.

6. each of the plurality of first polarized beams is incident on the illumination area at an incident angle of 0° or more and 44° or less, or 46° or more and 90° or less; 3. The wavelength beam combining device of claim 1, wherein each of the plurality of second polarized beams is incident on the illumination area at an angle of incidence between 0° and 44°, or between 46° and 90°.

7. the optical member has a polarization surface that separates the plurality of laser beams into the plurality of first polarized beams and the plurality of third polarized beams; 3. The wavelength beam combining device of claim 2, wherein each of the plurality of laser beams is incident on the polarization plane at an angle of incidence of 40 degrees or more and 50 degrees or less.

8. 3. The wavelength beam combining device according to claim 1, wherein the diffraction grating is a reflective diffraction grating and has a cooling structure.

9. the cooling structure is one or more cooling passages; 9. The wavelength beam combining device of claim 8, wherein the one or more cooling paths do not overlap the illuminated area when viewed in a direction parallel to the normal to the illuminated area.

10. 3. The wavelength beam combining device according to claim 1, wherein each of the plurality of laser beams is emitted from a semiconductor laser device via an optical fiber.

11. Further comprising a condenser lens and an optical fiber; 3. The wavelength beam combining device according to claim 1, wherein the condenser lens condenses the wavelength combined beam and inputs it into the optical fiber.

12. 12. The wavelength beam combining device of claim 11, wherein, when viewed in a direction parallel to the first polarization direction, the focusing lens and the optical fiber are surrounded by the optical paths of the plurality of first polarized beams and the optical paths of the plurality of second polarized beams.

13. 12. The wavelength beam combining device of claim 11, wherein when viewed in a direction parallel to the first polarization direction, the optical fiber has a portion that overlaps with the optical paths of the plurality of first polarized beams or the optical paths of the plurality of second polarized beams.

14. A wavelength beam combining device according to claim 1 or 2; a plurality of semiconductor laser devices each emitting a laser beam corresponding to one of the plurality of laser beams; A direct diode laser device comprising:

15. 15. The direct diode laser device of claim 14, further comprising an optical fiber array device configured to form one of the plurality of laser beams from the laser light emitted from each of the plurality of semiconductor laser devices.

16. At least one direct diode laser device according to claim 14; an optical transmission fiber coupled to the wavelength-combined 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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