Laser module and fiber laser device

Abstract

The laser module (20) includes: a first LD (31) emitting a first light (L1), a second LD (32) emitting a second light (L2), collimating lenses (36) and (37), and a wavelength combining element (45). The wavelength combining element (45) reflects the first light (L1) in a predetermined direction and causes the second light (L2) to overlap with the first light (L1) and be emitted in the predetermined direction. The fast axis of the first light (L1) incident on the wavelength combining element (45) is parallel to a first plane, and the fast axis of the second light (L2) incident on the wavelength combining element (45) is parallel to a second plane. The first plane and the second plane pass through the entire range of the first light (L1) from the reflector (44A2) to the wavelength combining element (45) and the entire range of the first light (L1) from the wavelength combining element (45) to the first focusing lens (46).

Description

Technical Field

[0001] This invention relates to a laser module and a fiber laser device, specifically to a laser module that combines and emits light of different wavelengths, and a fiber laser device equipped with the laser module. Background Technology

[0002] In recent years, there has been a demand for high output of emitted light in fiber laser devices. To achieve this high output, for example, the excitation light emitted from the laser module needs to be of high output. For instance, Patent Document 1 describes a laser module that enables high output of excitation light emitted from the laser module.

[0003] Regarding the laser module of Patent Document 1, it includes: multiple LDs (Laser Diodes) that emit light of a first wavelength, and multiple LDs that emit light of a second wavelength. These LDs are mounted with the active layer parallel to the mounting surface on which they are mounted. Therefore, the fast axis of the light emitted from the LDs is perpendicular to the mounting surface, and the slow axis is parallel to the mounting surface. Furthermore, the laser module of Patent Document 1 includes a wavelength combining element, which is vertically erected on the aforementioned mounting surface. Using this structure, multiple beams of different wavelengths are incident on the wavelength combining element with their slow axis direction parallel to the mounting surface, and are emitted from the wavelength combining element. As a result, according to Patent Document 1, spatially densely packed light can be generated, increasing the output of the excitation light emitted from the laser module.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: U.S. Patent Application Publication No. 2017 / 0271837 Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] As wavelength synthesis elements, diffraction gratings or volume Bragg gratings (VBGs) that periodically change the refractive index of a glass block are sometimes used. To obtain the desired diffraction efficiency, the incident angle of the light incident on these elements needs to accurately conform to the specified design value.

[0009] Furthermore, typically, the spread angle of light emitted from the LD along the fast axis is larger than that along the slow axis. However, typically, the width of light emitted from the LD along the slow axis is wider than that along the fast axis, resulting in poorer beam quality along the slow axis. Therefore, after light emitted from the LD passes through both the fast and slow axis collimating lenses, the spread angle of this light along the slow axis relative to the optical axis tends to be larger than that along the fast axis relative to the optical axis. In the laser module of Patent Document 1, after passing through the fast and slow axis collimating lenses, multiple beams of different wavelengths are incident on the wavelength combining element with their respective slow axes parallel to the planes of the optical axes of the beams incident on and out of the wavelength combining element. Therefore, when light is incident on the wavelength combining element with its slow axis parallel to the aforementioned plane, as in Patent Document 1, the light will contain a significant amount of light that is incident on the wavelength combining element at an angle different from the design value due to the large expansion angle of the slow axis. Consequently, for the laser module of Patent Document 1, there is a tendency for diffraction efficiency to decrease, resulting in reduced brightness of the light emitted from the laser module.

[0010] Therefore, the object of the present invention is to provide a laser module capable of emitting high-brightness light and a fiber laser device having the laser module.

[0011] (II) Technical Solution

[0012] To achieve the above objectives, the laser module of the present invention is characterized by: a first laser diode emitting a first light; a second laser diode emitting a second light with a wavelength different from the first light; a fast-axis collimating lens, respectively disposed corresponding to the first laser diode and the second laser diode, for collimating the light emitted from the first laser diode and the second laser diode in the fast-axis direction; a slow-axis collimating lens, respectively disposed corresponding to the first laser diode and the second laser diode, for collimating the light emitted from the first laser diode and the second laser diode in the slow-axis direction; and a wavelength combining element, which is composed of a VBG or a diffraction grating, for emitting and transmitting the first light emitted from the first laser diode through the fast-axis collimating lens and the slow-axis collimating lens, and the second light emitted from the second laser diode through the fast-axis collimating lens and the slow-axis collimating lens in the wavelength combining direction. A wavelength combining element is incident on the light source. The wavelength combining element reflects the first light in a predetermined direction and causes the second light to overlap with the first light and be emitted in the predetermined direction. The fast axis of the first light incident on the wavelength combining element is parallel to a first plane that passes through the entire interval from the optical element that directly incident the first light on the wavelength combining element to the first light of the wavelength combining element, and from the wavelength combining element to the optical element on which the first light emitted from the wavelength combining element directly incident. The fast axis of the second light incident on the wavelength combining element is parallel to a second plane that passes through the entire interval from the optical element that directly incident the first light on the wavelength combining element to the first light of the wavelength combining element, and from the wavelength combining element to the optical element on which the first light emitted from the wavelength combining element directly incident.

[0013] If a plane is defined as a reference plane, passing through the entire range from the optical element through which the first light is directly incident on the wavelength combining element to the optical axis of the first light from the wavelength combining element, and the entire range from the wavelength combining element to the optical element through which the first light emitted from the wavelength combining element is directly incident, then when the first light is incident on the wavelength combining element, the smaller the expansion component of the first light relative to the optical axis in the direction parallel to the reference plane, the more effectively the reduction in the diffraction efficiency of the first light in the wavelength combining element can be suppressed. Furthermore, the expansion component of the light incident on the wavelength combining element in the direction perpendicular to the reference plane has a smaller impact on the mutual interference of the light emitted from the wavelength combining element compared to the expansion component in the direction parallel to the reference plane. Since the aforementioned first plane passes through the entire range from the optical element through which the first light is directly incident on the wavelength combining element, and the entire range from the wavelength combining element to the optical element through which the first light emitted from the wavelength combining element is directly incident, it is therefore parallel or nearly parallel to the reference plane. Furthermore, the first plane need only pass through the first light as described above, and is not limited to passing through the optical axis of the first light; it can be slightly non-parallel to the plane passing through the optical axis of the first light. Additionally, as mentioned above, in a laser module, the optical spread angle relative to the optical axis in the fast axis direction is typically smaller than the optical spread angle relative to the optical axis in the slow axis direction. In this laser module, the fast axis of the first light is parallel to the first plane, therefore the fast axis of the first light is parallel or nearly parallel to the reference plane. Therefore, in this laser module, the spread angle of the first light in the direction parallel to the reference plane is small, which can suppress the reduction in diffraction efficiency of the first light. Furthermore, the second plane passes through the entire range from the optical element through which the first light is directly incident on the wavelength combining element to the first light in the wavelength combining element, and the entire range from the wavelength combining element to the optical element through which the first light emitted from the wavelength combining element is directly incident; therefore, it is parallel or nearly parallel to the reference plane. Furthermore, the second plane need only pass through the first light as described above, and is not limited to passing through the optical axis of the first light; it can be slightly non-parallel to the plane passing through the optical axis of the first light. Additionally, the second plane can be the same plane as the first plane, or it can be a different plane. It should be noted that even when the second plane is different from the first plane, the second plane is nearly parallel to the first plane. In this laser module, the fast axis of the second light is parallel to the second plane, therefore the fast axis of the second light is parallel or nearly parallel to the reference plane. Consequently, in this laser module, the spread angle of the second light in the direction parallel to the reference plane is small, which can suppress the reduction in diffraction efficiency of the second light. Thus, according to this laser module, since the reduction in diffraction efficiency of the first and second lights is suppressed respectively, the density of the emitted light can be increased and high-brightness light can be emitted.

[0014] Additionally, preferably, the first plane is connected to the optical axis of the first light incident on the wavelength combining element and the optical axis of the first light reflected from the wavelength combining element.

[0015] When the first plane passes through the optical axis of the first light as described above, the first plane is parallel to the aforementioned reference plane. Therefore, compared to when the first plane does not pass through the optical axis of the first light, the reduction in diffraction efficiency can be suppressed.

[0016] Furthermore, more preferably, the second plane is connected to the optical axis of the first light incident on the wavelength combining element and the optical axis of the first light reflected from the wavelength combining element.

[0017] When the second plane passes through the optical axis of the first light as described above, the second plane is parallel to the aforementioned reference plane. Therefore, compared to when the second plane does not pass through the optical axis of the first light, the reduction in diffraction efficiency can be suppressed.

[0018] Furthermore, more preferably, the device comprises a plurality of first laser diodes and a plurality of second laser diodes. Each first light emitted from the plurality of first laser diodes and each second light emitted from the plurality of second laser diodes are transmitted through the fast-axis collimating lens and the slow-axis collimating lens and incident on the wavelength combining element. The wavelength combining element reflects each first light in the predetermined direction and causes each second light to coincide with each first light in a one-to-one manner, and is emitted in the predetermined direction. In each pair of overlapping first and second lights, the fast axis of the first light incident on the wavelength combining element is parallel to the first plane in the pair, and the fast axis of the second light incident on the wavelength combining element is parallel to the second plane in the pair.

[0019] At this point, the fast axes of each of the multiple first beams are parallel to the first plane, and the fast axes of each of the multiple second beams are parallel to the second plane. Therefore, it is possible to suppress the reduction in diffraction efficiency for each of the multiple first beams and the multiple second beams individually. As a result, it is possible to increase the density of the light emitted as a whole and emit high-brightness light.

[0020] Furthermore, more preferably, when the laser module has multiple first laser diodes and multiple second laser diodes, the fast axes of each of the first beams incident on the wavelength combining element are parallel to each other.

[0021] At this point, compared to when at least a portion of the fast axes of the first beams incident on the wavelength combining element are not parallel to each other, the first beams can be brought closer together, allowing a higher density of first beams to be incident on the wavelength combining element. Therefore, it is possible to emit light with higher brightness.

[0022] In addition, preferably, when the laser module has a plurality of first laser diodes and a plurality of second laser diodes, the fast axis of each second light incident on the wavelength combining element is parallel to the fast axis of at least one first light.

[0023] At this point, compared to when the fast axes of the second beams incident on the wavelength combining element are not parallel to the fast axes of the first beams, the degree of overlap between the first and second beams can be increased, and the density of the first and second beams incident on the wavelength combining element can be increased. Therefore, higher brightness light can be emitted.

[0024] In addition, preferably, when the laser module has a plurality of first laser diodes and a plurality of second laser diodes, the fast axes of the second light incident on the wavelength combining element are parallel to each other.

[0025] At this point, compared to when at least a portion of the fast axes of the second beams incident on the wavelength combining element are not parallel to each other, the second beams can be brought closer together, allowing a high density of second beams to be incident on the wavelength combining element. Therefore, it is possible to emit light with higher brightness.

[0026] Alternatively, the wavelength of the light emitted from the first laser diode and the second laser diode may be above 970nm and below 982nm.

[0027] When using laser modules in fiber laser devices, ytterbium (Yb) is sometimes added as an active element to the core of the fiber used to amplify the light emitted from the laser module. One of the peak wavelengths in the absorption spectrum of light absorbed by ytterbium is approximately 970 nm to 982 nm. Therefore, if the wavelength of light emitted from multiple laser diodes is 970 nm to 982 nm, then when the amplifying fiber containing ytterbium is connected to the laser module, the amplifying fiber can effectively absorb the light.

[0028] Preferably, when the wavelength of the light emitted from the first laser diode and the second laser diode is above 970nm and below 982nm, the wavelength of the first light and the wavelength of the second light are between 976nm, and the difference between the wavelength of the first light and the wavelength of the second light is within 2nm.

[0029] If the difference between the wavelengths of the first and second lights is so small, then both the first and second lights have high absorption efficiency for ytterbium. Therefore, when the laser module is connected to an amplifying fiber with added ytterbium, the excitation efficiency in the amplifying fiber can be further improved.

[0030] In addition, preferably, the incident angle of the first light on the wavelength combining element and the incident angle of the second light on the wavelength combining element are both 3° or more.

[0031] If the incident angle is 3° or greater, the first and second rays are more likely to be emitted from the wavelength combining element in the specified direction compared to when the incident angle is less than 3°. Therefore, it is easy to construct a scheme that can suppress the first and second rays emitted from the wavelength combining element from being incident on optical elements that are different from the optical elements that should be incident on.

[0032] Alternatively, the wavelength synthesis element may be a VBG with apodization.

[0033] According to this structure, when sidelobes are generated in the distribution of diffraction efficiency of the VBG with respect to the wavelength of light incident on the VBG, these sidelobes can be reduced. As a result, even for light with short wavelength intervals, synthesis can be performed without interference from sidelobes.

[0034] Additionally, preferably, the total power of the first light reflected by the wavelength combining element and traveling in the predetermined direction is 80% or more relative to the total power of the first light incident on the wavelength combining element, and the total power of the second light emitted from the wavelength combining element and traveling in the predetermined direction is 80% or more relative to the total power of the second light incident on the wavelength combining element.

[0035] With this structure, more than 80% of the first and second rays incident on the wavelength combining element are emitted in a predetermined direction, thus further increasing the density of light emitted from the wavelength combining element.

[0036] In addition, in order to achieve the above objectives, the fiber laser device of the present invention is characterized by comprising: any of the laser modules described above; and an amplifying fiber that receives light emitted from the laser module and has an active element in its core that is excited by the light.

[0037] In this fiber laser device, because it includes any of the laser modules described above, the excitation light of the peak wavelength band of the active element converging in the amplifying fiber can be incident on the amplifying fiber with high density and high brightness. Therefore, the excitation light propagating in the amplifying fiber is of high density and high brightness, which improves the absorption efficiency of the excitation light in the amplifying fiber.

[0038] Alternatively, in the aforementioned fiber laser device, the wavelengths of the first light and the second light may be located on the low-wavelength side and the high-wavelength side, respectively, sandwiched between the peak wavelengths of the absorption spectrum of the light absorbed by the active element.

[0039] For laser diodes installed in the same laser module, their external environment and driving conditions are roughly the same. Therefore, the wavelength shift of the light emitted from each laser diode tends to be in the same direction, and both tend to shift towards longer or shorter wavelengths. Thus, if the wavelengths of the first and second light are located between the aforementioned peak wavelengths and at the low and high wavelength sides, when the wavelength shift of the light emitted from each laser diode, for example, towards the longer wavelength side, occurs due to temperature changes in the fiber laser device, the wavelength of the light between the peak wavelengths and located at the low wavelength side can shift towards the side with increased absorption of the active element, while the wavelength of the light at the high wavelength side can shift towards the side with decreased absorption of the active element. Therefore, when wavelength shift occurs, the absorption rates of the first and second light on the active element can be balanced overall, suppressing state changes in the laser device caused by changes in the absorption rate of the excitation light on the active element.

[0040] Preferably, when the wavelengths of the first light and the second light are located on the low-wavelength side and the high-wavelength side respectively, between the peak wavelengths of the absorption spectrum of the light absorbed by the active element, the absorption rate of the first light on the active element is equal to that of the second light on a portion of the operating temperature of the fiber laser device.

[0041] When there is a difference between the absorption rates of the first and second beams of the active element, the difference in absorption rates needs to be considered when designing the amount of active element to be added, the length of the fiber optic cable for amplification, etc. On the other hand, as mentioned above, if the absorption rates of the first and second beams of the active element are the same within a certain range of the operating temperature of the fiber laser device, the amount of active element to be added can be determined based on a single absorption rate, making the design of the laser device easier.

[0042] As described above, according to the present invention, a laser module capable of emitting high-brightness light and a fiber laser device incorporating the laser module can be provided. Attached Figure Description

[0043] Figure 1 This is a diagram showing the structure of the fiber laser device according to the first embodiment of the present invention.

[0044] Figure 2 It means Figure 1 The diagram shows a cross-section of the optical fiber perpendicular to its length direction, as shown in the enlarged diagram.

[0045] Figure 3This is a top view of the laser module of the first embodiment of the present invention, viewed from a direction perpendicular to the active layer of the laser diode.

[0046] Figure 4 It is a diagram showing the state of light incident on an optical rotator.

[0047] Figure 5 It means Figure 3 A three-dimensional view of an example of an optical rotator shown.

[0048] Figure 6 It is a diagram showing the state of light emitted from the optical rotator.

[0049] Figure 7 It is a summary representation Figure 3 A diagram showing the state near the wavelength synthesizing element.

[0050] Figure 8 This is a graph representing the absorption spectrum of light absorbed by the active elements.

[0051] Figure 9 Therefore, with Figure 3 The same viewing angle is used to show the top view of the laser module of the second embodiment of the present invention.

[0052] Figure 10 Therefore, with Figure 7 A diagram showing a first modified example of the laser module of the present invention, viewed from the same angle.

[0053] Figure 11 Therefore, with Figure 7 A second modified example of the laser module of the present invention is shown from the same viewing angle.

[0054] Figure 12 Therefore, with Figure 7 A figure showing a third modified example of the laser module of the present invention is presented from the same viewing angle. Detailed Implementation

[0055] The following description, in conjunction with the accompanying drawings, illustrates embodiments of the laser module and fiber laser device of the present invention. The illustrated embodiments are provided to facilitate understanding of the invention and are not intended to limit its scope. Modifications and improvements can be made to the following embodiments without departing from their spirit. Furthermore, the dimensions of various components may be exaggerated in this specification for ease of understanding.

[0056] (First Implementation)

[0057] Figure 1 This is a diagram showing the structure of the fiber laser device according to the first embodiment. (Example) Figure 1As shown, the fiber laser device 1 of this embodiment includes, as its main structure, an excitation source 2, an optical combiner 3, an amplification fiber 5, an optical fiber 4 connected to one side of the amplification fiber 5, a first FBG (Fiber Bragg Grating) 7 disposed on the optical fiber 4, an optical fiber 6 connected to the other side of the amplification fiber 5, and a second FBG 8 disposed on the optical fiber 6. In this fiber laser device 1, the amplification fiber 5, the first FBG 7, and the second FBG 8 constitute a resonator. The fiber laser device 1 is typically used at a temperature of 0°C or higher and 60°C or lower, but it can also be used at temperatures outside this range, or at lower or higher temperatures.

[0058] Figure 2 It means Figure 1 The diagram shows a magnified cross-section of the optical fiber 5 perpendicular to its length direction. (See diagram for example.) Figure 2 As shown, the amplifying optical fiber 5 comprises, as its main structure, a fiber core 5a, an inner cladding 5b that surrounds the outer periphery of the fiber core 5a without gaps, an outer cladding 5c ​​that covers the outer periphery of the inner cladding 5b, and a cladding layer 5d that covers the outer cladding 5c, forming a so-called double-cladding structure. The refractive index of the inner cladding 5b is lower than that of the fiber core 5a, and the refractive index of the outer cladding 5c ​​is lower than that of the inner cladding 5b.

[0059] Examples of materials constituting the fiber core 5a include quartz containing elements such as germanium (Ge) to increase its refractive index and ytterbium (Yb) to be excited by excitation light emitted from the excitation source 2. In addition to these elements, aluminum (Al) and phosphorus (P) may be added as needed. Rare earth elements are examples of such active elements, including thulium (Tm), cerium (Ce), neodymium (Nd), europium (Eu), and erbium (Er) in addition to Yb. Furthermore, bismuth (Bi) may be an example of an active element in addition to rare earth elements. In this embodiment, ytterbium is added as an active element.

[0060] As a material constituting the inner cladding layer 5b, pure quartz without any added dopants can be cited as an example. Alternatively, elements such as fluorine (F) that lower the refractive index can be added to the material of the inner cladding layer 5b. The outer cladding layer 5c is composed of resin or quartz. As a resin, an ultraviolet-curable resin can be cited as an example. As quartz, a type of quartz can be cited as having added dopants such as fluorine (F) that lower the refractive index, resulting in a refractive index lower than that of the inner cladding layer 5b. As a material constituting the coating layer 5d, an ultraviolet-curable resin can be cited as an example. When the outer cladding layer 5c is resin, an ultraviolet-curable resin different from the resin constituting the outer cladding layer is used.

[0061] The optical fiber 4, connected to one side of the amplifying optical fiber 5, comprises, as its main structure: a core without added active elements, an inner cladding that surrounds the outer peripheral surface of the core without gaps, an outer cladding that covers the outer peripheral surface of the inner cladding, and a cladding layer that covers the outer cladding. Except for the absence of added active elements, the diameter and refractive index of the core of the optical fiber 4 are approximately the same as those of the core 5a of the amplifying optical fiber 5. The core of the optical fiber 4 is connected to the core 5a of the amplifying optical fiber 5, and the inner cladding of the optical fiber 4 is connected to the inner cladding 5b of the amplifying optical fiber 5. Furthermore, a first FBG7, serving as a first reflector, is provided on the core of the optical fiber 4. Thus, the first FBG7 is optically coupled to the core 5a of the amplifying optical fiber 5 on one side. The first FBG7 is configured such that the portion with a high refractive index repeats periodically along the length of the optical fiber 4, and by adjusting this period, at least a portion of the wavelength of light emitted by the active element of the amplifying optical fiber 5 in its excited state can be reflected. The reflectivity of the first FBG7 is higher than that of the second FBG8, which will be described later, for example, reflecting more than 99% of the light of the desired wavelength emitted by the active element. In addition, for the wavelength of the light reflected by the first FBG7, as mentioned above, when the active element is ytterbium, it is, for example, 1070 nm.

[0062] In the optical fiber 6 connected to the other side of the amplifying optical fiber 5, the main structure includes: a core without added active elements, a cladding that surrounds the outer peripheral surface of the core without gaps, and a cladding layer covering the outer peripheral surface of the cladding. The core of the optical fiber 6 is connected to the core 5a of the amplifying optical fiber 5, and the cladding of the optical fiber 6 is connected to the inner cladding 5b of the amplifying optical fiber 5. Furthermore, a second FBG8, serving as a second reflector, is provided on the core of the optical fiber 6. Thus, the second FBG8 is optically coupled to the core 5a of the amplifying optical fiber 5 on the other side of the amplifying optical fiber 5. The second FBG8 is configured such that the high refractive index portion repeats at a constant period along the length of the optical fiber 6, and reflects at least a portion of the wavelengths of light reflected by the first FBG7 with a lower reflectivity than the first FBG7. The second FBG8 reflects at least a portion of the wavelengths of light reflected by the first FBG7 with a reflectivity, for example, 5% to 50%. In addition, in this embodiment, the other end of the fiber 6 on the opposite side of the fiber 5 used for amplification is not specifically connected, but a glass rod or the like with a diameter larger than the core diameter of the fiber 6 can also be connected as part of the processing head.

[0063] The excitation source 2 includes multiple laser modules 20 and optical fibers 11 connected to each laser module 20. The core of each optical fiber 11 is connected to the inner cladding of an optical fiber 4 via an optical combiner 3. Thus, the core of the optical fiber 11 that propagates the excitation light emitted from each laser module 20 is optically coupled to the inner cladding 5b of the amplification optical fiber 5 via the inner cladding of the optical fiber 4.

[0064] Figure 3 This is a top view of the laser module 20. (For example...) Figure 3 As shown, the laser module 20 includes: an optical element assembly (described later), a mounting substrate 21 on which the optical element assembly is mounted, and a cover (not shown) that covers the mounting substrate 21 and houses the optical element assembly together with the mounting substrate 21.

[0065] The mounting substrate 21 includes a flat plate portion 22 and a stepped portion 23 formed in a stepped shape. The aforementioned optical fiber 11 is connected near the edge on the opposite side of the stepped portion 23 side of the flat plate portion 22.

[0066] The stepped section 23 is configured to form a step difference in a first direction perpendicular to the flat plate section 22. If the surface of the flat plate section 22 is set as the zeroth level, then in this embodiment, the stepped section 23 has a step difference of six levels along the first direction. The first level of the stepped section 23 is the level closest to the flat plate section 22 and is the lowest level in the stepped section 23. As the number of levels increases, the distance from the flat plate section 22 becomes farther, and the height from the surface of the flat plate section 22 becomes higher. Furthermore, the number of levels of the stepped section 23 is not limited to six levels. The surface of each level is parallel to the surface of the flat plate section 22, and the aforementioned optical element assembly is mounted on the surface of the flat plate section 22 and the surface of each level. Therefore, the surface of the flat plate section 22 and the surface of each level are sometimes referred to together as the mounting surface 21F. The direction perpendicular to this mounting surface 21F is the aforementioned first direction. In addition, the surface of each level is formed as mutually parallel strips, and the length direction of each level is along one of the directions perpendicular to the first direction, namely the second direction. The direction perpendicular to both the first and second directions is the third direction.

[0067] The optical element assembly mounted on mounting surface 21F includes: multiple laser diodes (LDs), multiple fast-axis collimating lenses 36, multiple slow-axis collimating lenses 37, multiple mirrors 39, two optical rotators 40, two wavelength stabilizing elements 43, a pair of mirrors 44A1 and 44A2, a pair of mirrors 44B1 and 44B2, a wavelength combining element 45, a first condenser lens 46, and a second condenser lens 47. In this optical element assembly, the two optical rotators 40, the two wavelength stabilizing elements 43, the pair of mirrors 44A1 and 44A2, the pair of mirrors 44B1 and 44B2, the wavelength combining element 45, the first condenser lens 46, and the second condenser lens 47 are disposed on the flat plate portion 22. Furthermore, the multiple LDs, the multiple fast-axis collimating lenses 36, the multiple slow-axis collimating lenses 37, and the multiple mirrors 39 are disposed on the stepped portion 23.

[0068] The plurality of LDs includes: a first LD group 31G, which is composed of a plurality of first LDs 31 disposed on one side of the mounting substrate 21 in the second direction; and a second LD group 32G, which is composed of a plurality of second LDs 32 disposed on the other side. One first LD 31 and one second LD 32 are disposed on each level surface of the stepped portion 23. Furthermore, the first LD 31 and the second LD 32 each have a Fabry-Perot structure formed by stacking a plurality of semiconductor layers including an active layer, disposed in a manner parallel to the mounting surface 21F. Additionally, the first LD 31 emits light along the second direction toward the side of the second LD 32 disposed at the same level, and the second LD 32 emits light along the second direction toward the opposite side of the side of the first LD 31 disposed at the same level. Therefore, the fast axis direction of the light emitted from the first LD 31 and the second LD 32 is parallel to the first direction. In addition, the slow axis direction of the light emitted from the first LD31 and the second LD32 is parallel to the mounting surface 21F and parallel to the third direction which is perpendicular to the second direction.

[0069] The first LD31 and the second LD32 emit light in a wavelength band of 970 nm or more and 982 nm or less. More specifically, they emit light in a wavelength band of 970 nm or more and 980 nm or less. The wavelengths of the first light L1 emitted by the first LD31 and the second light L2 emitted by the second LD32 are different from each other. In this embodiment, the interval between these wavelengths is, for example, within 2 nm, and the wavelength of the first light L1 is, for example, approximately 975 nm, and the wavelength of the second light L2 is, for example, approximately 977 nm.

[0070] Multiple fast-axis collimating lenses 36 are arranged in a one-to-one correspondence with multiple LDs, and are set at the same level as the corresponding LDs. The fast-axis collimating lenses 36 are arranged near the emission surfaces of LDs 31 and 32 to collimate the light component that extends in the fast-axis direction emitted from LDs 31 and 32.

[0071] Multiple slow-axis collimating lenses 37 are arranged in a one-to-one correspondence with multiple LDs, and are set at the same level as the corresponding LDs. The slow-axis collimating lenses 37 and fast-axis collimating lenses 36 are arranged along the second direction to collimate the light that has been transmitted through the fast-axis collimating lens 36 and has been extended in the slow-axis direction.

[0072] Multiple mirrors 39 are arranged in a one-to-one correspondence with multiple LDs, and are positioned at the same level as the corresponding LDs. The mirrors 39, fast-axis collimating lenses 36 and slow-axis collimating lenses 37 are arranged along the second direction, and each has a reflective surface that reflects light transmitted through the slow-axis collimating lens 37. This reflective surface is inclined at approximately 45° relative to the second direction. Therefore, the light reflected by the mirrors 39 propagates along the third direction towards the aforementioned flat plate portion 22.

[0073] Figure 4 This is a diagram showing the state of the first light L1 at the moment it is emitted from each of the first LD31, reflected by the reflector 39, and reaches the boundary between the stepped section 23 and the flat section 22. Figure 4 In the diagram, each first beam L1 is represented by a cross-section perpendicular to the mounting surface 21F and orthogonal to the third direction. For example... Figure 4 As shown, the first light L1 emitted from each first LD31 is an elliptical shape with its major axis parallel to the mounting surface 21F. Figure 4 The diagram illustrates the state of the first light L1 after reflection by mirror 39. Reference numeral S indicates the slow axis direction of the first light L1, and reference numeral F indicates the fast axis direction. This fast axis direction is parallel to the first direction, as described above. Each first light L1 is arranged along the fast axis direction, i.e., the first direction, using the aforementioned six-level stepped portions 23. In this embodiment, each first light L1 is an approximately equal-sized elliptical shape, and each optical axis LA1 is arranged in a straight line along the first direction.

[0074] Furthermore, regarding the state of the second light L2 emitted from the second LD group 32G and reflected by the reflector 39, reaching the boundary between the stepped section 23 and the flat section 22, it is also related to... Figure 4 The first light L1 shown is in the same state. Therefore, the six second lights L2 are each an ellipse of approximately equal size, and their optical axes LA2 are arranged in a straight line along the first direction.

[0075] like Figure 3As shown, one of the two optical rotators 40 is disposed in each optical path of the first light L1 and arranged along the third direction together with the reflector 39 corresponding to the first LD group 31G. The other optical rotator 40 is disposed in each optical path of the second light L2 and arranged along the third direction together with the reflector 39 corresponding to the second LD group 32G. These optical rotators 40 have the same structure as each other. Therefore, the above-mentioned optical rotator 40 will be described.

[0076] Figure 5 This is a perspective view showing an example of the optical rotator 40. Furthermore, in Figure 5 To avoid complicating the diagram, only one of the first beams L1 incident on the optical rotator 40 is shown. Figure 5 As shown, the optical rotator 40 includes a first reflecting member 41 disposed on the lower side in the first direction and a second reflecting member 42 disposed on the upper side. A reflecting surface 41r is provided on the stepped portion 23 side of the first reflecting member 41 in the third direction, and the reflecting surface 41r is inclined at approximately 45° with respect to the surface of the flat plate portion 22. A reflecting surface 42r is provided directly above the reflecting surface 41r of the second reflecting member 42, and the reflecting surface 42r is inclined at approximately 45° with respect to the surface of the flat plate portion 22. The reflecting surface 42r is the side of the second reflecting member 42 opposite to the side of the other optical rotator 40. Therefore, for each first light L1 reflected by the mirror 39 and propagating in the third direction, when each first light L1 is incident on the reflecting surface 41r of the first reflecting member 41, it is reflected on the upper side of the reflecting surface 41r in the first direction. As a result, the fast axis of the first light L1 is parallel to the third direction. Furthermore, during this stage, the slow axis of the first light L1 remains parallel to the second direction. In this state, the first light L1 propagates upward in the first direction and is incident on the reflecting surface 42r of the second reflecting component 42 located above.

[0077] As described above, the reflecting surface 42r is tilted at 45°. Therefore, the first light L1 reflected by the reflecting surface 41r is reflected by the reflecting surface 42r and propagates to the opposite side of the other optical rotator 40 in the second direction. Figure 6 This is a diagram showing the state of the first light L1 reflected at the reflecting surface 42r. Figure 6 In the diagram, each first beam L1 is represented by a cross-section perpendicular to the mounting surface 21F and orthogonal to the second direction. For example... Figure 6As shown, the first light L1 emitted from the optical rotator 40 is reflected by the reflecting surface 42r, resulting in a state where the slow axis is parallel to the first direction and the fast axis is parallel to the third direction. Furthermore, in this embodiment, after being emitted from the optical rotator 40, each first light L1 is an elliptical shape of approximately the same size, and each optical axis LA1 is aligned in a straight line along the third direction parallel to the mounting surface 21F. Therefore, in this embodiment, the optical axis LA1 of each first light L1 emitted from the optical rotator 40 has the same height in the first direction.

[0078] The second light L2 is reflected on another optical rotator 40 in the same manner as the first light L1, and becomes the same as... Figure 6 The first light is in the same state as shown. Furthermore, in this embodiment, after being emitted from the optical rotation element 40, the height of the optical axis of the second light L2 in the first direction is the same as the height of the optical axis LA1 of each of the first lights L1 in the first direction.

[0079] One of the two wavelength stabilizing elements 43 is disposed in each optical path of the first light L1 reflected by the optical rotator 40, and is aligned with the optical rotator 40 along the second direction. Therefore, the first light L1 reflected by the optical rotator 40 is incident on one wavelength stabilizing element 43. The other wavelength stabilizing element 43 is disposed in each optical path of the second light L2 reflected by the other optical rotator 40, and is aligned with the optical rotator 40 along the second direction. Therefore, the second light L2 reflected by the optical rotator 40 is incident on the other wavelength stabilizing element 43.

[0080] In this embodiment, a wavelength stabilizing element 43 is an optical element that transmits a portion of light with a wavelength of approximately 975 nm and reflects another portion; in this embodiment, it is a VBG or a diffraction grating. As described above, the wavelength of the first light L1 is approximately 975 nm. Therefore, the aforementioned other portion of the first light L1 incident on the wavelength stabilizing element 43 is reflected by the wavelength stabilizing element 43 and returns to the first LD group 31G. Thus, the wavelength stabilizing element 43 and the first LD group 31G constitute a resonator, and the gain and loss within the resonator are equalized, thereby causing the first light L1 with a wavelength of approximately 975 nm to be in an excited state.

[0081] In this embodiment, another wavelength stabilizing element 43 is an optical element that transmits a portion of light with a wavelength of approximately 977 nm and reflects another portion; it is a VBG or a diffraction grating. Therefore, the resonator is formed by this wavelength stabilizing element 43 and the second LD group 32G, and the second light L2 with a wavelength of approximately 977 nm is in an excited state.

[0082] Mirror 44A1 of a pair of mirrors 44A1 and 44A2 reflects multiple first beams L1 emitted from a wavelength stabilizing element 43 toward mirror 44A2. Mirror 44A2 then reflects the first beams L1 reflected by mirror 44A1 toward wavelength combining element 45. Similarly, mirror 44B1 of a pair of mirrors 44B1 and 44B2 reflects multiple second beams L2 emitted from another wavelength stabilizing element 43 toward mirror 44B2. Mirror 44B2 then reflects the second beams L2 reflected by mirror 44B1 toward wavelength combining element 45. Thus, the multiple first beams L1 propagate toward wavelength combining element 45 with their fast axis parallel to the mounting surface 21F and their slow axis parallel to a first direction perpendicular to the mounting surface 21F. Likewise, the multiple second beams L2 propagate toward wavelength combining element 45 with their fast axis parallel to the mounting surface 21F and their slow axis parallel to a first direction perpendicular to the mounting surface 21F.

[0083] Furthermore, in this embodiment, each first light L1 reflected by reflectors 44A1 and 44A2 is an ellipse of approximately the same size with its major axis parallel to the first direction, and the height of each optical axis LA1 in the first direction from the surface of the plate portion 22 is the same. Similarly, each second light L2 reflected by reflectors 44B1 and 44B2 is an ellipse of approximately the same size with its major axis parallel to the first direction, and the height of each optical axis in the first direction from the surface of the plate portion 22 is the same. In addition, the height of the optical axis LA1 of the first light L1 reflected by reflectors 44A1 and 44A2 is the same as the height of the optical axis LA2 of the second light L2 reflected by reflectors 44B1 and 44B2.

[0084] The wavelength combining element 45 is disposed near the edge of the stepped portion 23 on the opposite side of the plate portion 22, that is, on the opposite side of the optical fiber 11. In this embodiment, the wavelength combining element 45 is a diffraction grating, on which a plurality of grooves (not shown) are formed in a predetermined pattern. These grooves extend approximately along the slow axis direction of each of the first light L1 and the second light L2 that are about to be incident on the wavelength combining element 45. Therefore, the wavelength combining element 45 of this embodiment has a reflective surface 45r on which a plurality of grooves extending approximately along a first direction are formed. Examples of such diffraction gratings include reflective diffraction gratings, blazed diffraction gratings, or holographic diffraction gratings.

[0085] The first light L1 reflected by mirror 44A2 is incident on the wavelength combining element 45. Therefore, mirror 44A2 is an optical element that allows the first light L1 to directly enter the wavelength combining element 45. Additionally, the second light L2 reflected by mirror 44B2 is incident on the wavelength combining element 45. Therefore, mirror 44B2 is an optical element that allows the second light L2 to directly enter the wavelength combining element 45.

[0086] Figure 7 This is a diagram showing the state of the wavelength combining element around 45 nm. (For example...) Figure 7 As shown, the wavelength combining element 45 is inclined along the first direction and at a predetermined angle relative to the second and third directions. In this embodiment, the first incident angle of each first light L1 incident on the wavelength combining element 45 and the second incident angle of each second light L2 incident on the wavelength combining element 45 are different. Each first light L1 and each second light L2 incident on the wavelength combining element 45 at approximately the same position, each second light L2 coincides with each first light L1 one by one, and the first light L1 and the second light L2 coincide in a one-to-one manner, forming a combined light SL. Therefore, each combined light SL includes a first light L1 and a second light L2. Furthermore, in Figure 7 In order to prevent the diagram from becoming complicated, two first beams L1 and two second beams L2 are shown.

[0087] The wavelength combining element 45 is configured such that, when the first light L1 is incident at a first incident angle and the second light L2 is incident at a second incident angle, the first light L1 and the second light L2 are reflected and emitted in approximately the same predetermined direction. In this embodiment, the predetermined direction is along the second direction and toward the fiber 11 side. Therefore, each first light L1 and each second light L2 incident on the wavelength combining element 45 is reflected by the wavelength combining element 45 along the second direction toward the fiber 11 side. Furthermore, the first light L1 and the second light L2 are emitted from the wavelength combining element 45 by reflection. The combined light SL, including the first light L1 and the second light L2 emitted from the wavelength combining element 45, is incident on the first condenser lens 46. Therefore, the first condenser lens 46 is an optical element in which the first light L1 and the second light L2 emitted from the wavelength combining element 45 are directly incident. In this embodiment, the fast axis of each first light L1 emitted from the wavelength combining element 45 is parallel to the third direction parallel to the mounting surface 21F, and the height of each optical axis LA1 in the first direction is consistent. Similarly, the fast axis of each second light L2 emitted from the wavelength combining element 45 is parallel to the third direction parallel to the mounting surface 21F, and the optical axes LA2 are at the same height in the first direction. Furthermore, the optical axes LA1 and LA2 of the lights L1 and L2 emitted from the wavelength combining element 45 are at the same height in the first direction. Thus, multiple composite beams SL are formed, each overlapping a first light L1 and a second light L2, and these composite beams SL propagate toward the optical fiber 11.

[0088] Here, the overlapping first light L1 and second light L2 are paired. In each pair, a first plane is defined. This first plane passes through the entire interval from the optical element (mirror 44A2) through which the first light L1 is directly incident on the wavelength combining element 45 to the optical axis LA1 of the first light L1 on the wavelength combining element 45, and the entire interval from the wavelength combining element 45 to the optical element (first condenser lens 46) through which the first light L1 emitted from the wavelength combining element 45 is directly incident. This first plane is defined according to each first light L1. In this embodiment, each first plane defined according to each first light L1 can be made parallel to the mounting surface 21F. At this time, the fast axis of each first light L1 incident on the wavelength combining element 45 is parallel to the first plane in the above pair. In addition, as mentioned above, the height of the optical axis LA1 of each first light L1 incident on the wavelength combining element 45 is the same, so the height of each first plane is the same. Therefore, in this embodiment, each first plane can be contained in a mutually repeating planar reference plane SF. Furthermore, in Figure 7 The image shows only a portion of the datum plane SF.

[0089] Furthermore, by pairing the overlapping first light L1 and second light L2 in each first light L1 and each second light L2, a second plane is defined in each pair. This second plane passes through the entire interval of the optical axis LA1 of the first light L1 from the reflector 44A2 to the wavelength combining element 45, and the entire interval of the optical axis LA1 of the first light L1 from the wavelength combining element 45 to the first condenser lens 46. This second plane is defined according to each second light L2. In this embodiment, each second plane defined according to each second light L2 can be made parallel to the mounting surface 21F. At this time, the fast axis of each second light L2 incident on the wavelength combining element 45 is parallel to the second plane in the aforementioned pair. Furthermore, as described above, the height of the optical axis LA2 of each second light L2 incident on the wavelength combining element 45 is the same as the height of the optical axis LA1 of each first light L1 incident on the wavelength combining element 45, and the height of the optical axis LA2 of each second light L2 reflected by the wavelength combining element 45 is the same as the height of the optical axis LA1 of each first light L1 reflected by the wavelength combining element 45. Therefore, it is possible to make the height of each second plane the same as the height of the first plane. Therefore, in this embodiment, it is possible to include each second plane in the aforementioned reference plane SF.

[0090] Furthermore, the first and second incident angles can be, for example, 3° or more and less than 90°, or 3° or more and less than 45°. If the incident angle is 3° or more, compared to when the incident angle is less than 3°, it makes it easier for the first light L1 and the second light L2 to exit from the wavelength combining element 45 in the desired direction. Therefore, it is easy to construct a scheme that can suppress the first light L1 and the second light L2 emitted from the wavelength combining element 45 from entering an optical element different from the optical element that should be incident on.

[0091] Furthermore, in this embodiment, the wavelength combining element 45 is configured such that the total power of the first light L1 reflected by the wavelength combining element 45 and traveling towards the optical fiber 11 along the second direction is 80% or more relative to the total power of the first light L1 incident on the wavelength combining element 45. Additionally, the wavelength combining element 45 is configured such that the total power of the second light L2 emitted from the wavelength combining element 45 and traveling towards the optical fiber 11 along the second direction is 80% or more relative to the total power of the second light L2 incident on the wavelength combining element 45.

[0092] like Figure 3 As shown, the first condenser lens 46, which directly incident on the first light L1 and the second light L2 emitted from the wavelength combining element 45, is arranged along the second direction with the wavelength combining element 45. The first condenser lens 46 is a lens that focuses the combined light SL of the incident first light L1 and the second light L2 in the fast axis direction. Therefore, each combined light SL emitted from the wavelength combining element 45 is incident on the first condenser lens 46 and focused in the fast axis direction, i.e., the third direction.

[0093] The second condenser lens 47 and the first condenser lens 46 are arranged along the second direction. The second condenser lens 47 is a lens that focuses the incident composite light SL in the slow axis direction. Therefore, the composite light SL emitted from the first condenser lens 46 is focused in the slow axis direction, i.e., the first direction.

[0094] Optical fiber 11 and second condenser lens 47 are aligned along the second direction. Furthermore, the core of optical fiber 11 is positioned in the optical path through which light transmitted via second condenser lens 47 passes. Therefore, the composite light SL, transmitted via second condenser lens 47, is incident on the core of optical fiber 11 and propagates within it. Moreover, the composite light SL comprises a plurality of first light L1 with a wavelength of approximately 975 nm and a plurality of second light L2 with a wavelength of approximately 977 nm.

[0095] Next, the operation of the fiber laser device 1 will be explained.

[0096] When a predetermined power is supplied to each laser module 20 constituting the excitation source 2, a plurality of first beams L1 with a wavelength of approximately 975 nm are emitted from the first LD group 31G, and a plurality of second beams L2 with a wavelength of approximately 977 nm are emitted from the second LD group 32G. These beams are combined by the aforementioned optical elements of the laser module 20 and propagate as excitation light in the core of the optical fiber 11. The excitation light emitted from each laser module 20 is combined by the optical combiner 3. The combined excitation light is incident on the inner cladding 5b of the amplification optical fiber 5 via the inner cladding of the optical fiber 4. The inner cladding 5b is sandwiched by a core 5a with a higher refractive index than the inner cladding 5b and an outer cladding 5c ​​with a lower refractive index than the inner cladding 5b. The excitation light incident on the inner cladding 5b mainly propagates in the inner cladding 5b and is incident on the core 5a. In this way, the excitation light incident on the core 5a excites the ytterbium, which is added to the core 5a as an active element.

[0097] Figure 8 This is a graph showing the absorption spectrum of light absorbed by the active element, ytterbium. For example... Figure 8 As shown, one of the peak wavelength bands in the absorption spectrum of ytterbium is approximately 970 nm to 982 nm. More specifically, this peak wavelength band is approximately 970 nm to 980 nm, and the peak value within this peak wavelength band is approximately 976 nm. Furthermore, the absorption rate of ytterbium by light with a wavelength of approximately 975 nm (approximately the lower wavelength side of the peak wavelength of approximately 976 nm) and the absorption rate of ytterbium by light with a wavelength of approximately 977 nm (approximately the higher wavelength side of the peak wavelength) can be considered the same, for example, at a typical operating temperature of 0°C to 60°C, which is a portion of the operating temperature of the aforementioned fiber laser device 1. In this embodiment, the light with a wavelength of approximately 975 nm (approximately the lower wavelength side of the peak wavelength) and the light with a wavelength of approximately 977 nm (approximately the higher wavelength side) are the excitation light.

[0098] Ytterbium, in its excited state, emits spontaneous emission light of a specific wavelength. This spontaneous emission light contains a wavelength of 1070 nm and has a specific wavelength band. This spontaneous emission light propagates in the core 5a of the amplifying fiber 5. A portion of this wavelength is reflected by the first FBG7. Of this reflected light, the wavelength reflected by the second FBG8 is reflected again and oscillates within the resonator. Furthermore, as the light reflected by the first FBG7 and the second FBG8 propagates in the core 5a of the amplifying fiber 5, stimulated emission occurs, amplifying the light. When the gain and loss within the resonator are equal, it enters a laser-excited state. Additionally, a portion of the light resonating between the first FBG7 and the second FBG8 is transmitted through the second FBG8 and exits from the end of the fiber 6.

[0099] When the fiber laser device 1 is, for example, a laser processing device, light emitted from the end of the fiber 6 is directed onto the workpiece via a processing head (not shown) for processing the workpiece.

[0100] As described above, the laser module 20 of this embodiment includes: a plurality of first LDs 31 that emit first light L1; a plurality of second LDs 32 that emit second light L2; a fast-axis collimating lens 36 and a slow-axis collimating lens 37, which are disposed corresponding to each of the first LDs 31 and each of the second LDs 32 to collimate the light emitted from each LD 31, 32; and a wavelength combining element 45, which is composed of a diffraction grating. Furthermore, each first light L1 transmitted through the collimating lenses 36, 37 and each second light L2 transmitted through the collimating lenses 36, 37 are incident on the wavelength combining element 45. Additionally, the wavelength combining element 45 reflects each first light L1 toward the fiber 11 side in the second direction and emits each second light L2 toward the fiber 11 side in the second direction, so that each first light L1 and each second light L2 coincide in a one-to-one correspondence. Furthermore, in each of the multiple pairs of overlapping first light L1 and second light L2, the fast axis of the first light L1 incident on the wavelength combining element 45 is parallel to a first plane that passes through the entire interval from the reflector 44A2 to the optical axis LA1 of the first light L1 from the wavelength combining element 45 and the optical axis LA1 of the first light L1 from the wavelength combining element 45 to the first condenser lens 46. Similarly, the fast axis of the second light L2 incident on the wavelength combining element 45 is parallel to a second plane that passes through the entire interval from the reflector 44A2 to the optical axis LA1 of the first light L1 from the wavelength combining element 45 and the optical axis LA1 of the first light L1 from the wavelength combining element 45 to the first condenser lens 46. Moreover, as described above, in this embodiment, each first plane defined according to the first light L1 and each second plane defined according to the second light L2 are contained within a reference plane SF.

[0101] In this laser module 20, the fast axis of each first beam L1 incident on the wavelength combining element 45 is parallel to the reference plane SF, which includes all the first planes defined by the first beams L1. Typically, the width of the light emitted from the LD in the slow axis direction is wider than that in the fast axis direction, and the beam quality in the slow axis direction is worse than that in the fast axis direction. Therefore, when the light emitted from the LD passes through the fast-axis collimating lens and the slow-axis collimating lens, the component of the light in the slow axis direction is more difficult to collimate compared to the component in the fast axis direction. As a result, after passing through the fast-axis collimating lens and the slow-axis collimating lens, the spread angle of the light relative to the optical axis in the slow axis direction is more likely to be larger than the spread angle relative to the optical axis in the fast axis direction. For a typical laser module, after passing through a fast-axis collimating lens and a slow-axis collimating lens, the spread angle of light in the fast-axis direction is approximately 0.05° to 0.1°, while the spread angle of light in the slow-axis direction is approximately 0.5° to 1°, with the former being an order of magnitude smaller than the latter. Therefore, since the fast axis of each first beam L1 incident on the wavelength combining element 45 is parallel to the reference plane SF, the spread component of the first beam L1 in the direction parallel to the reference plane SF is less than when the slow axis of the first beam L1 is parallel to the reference plane SF. Therefore, the diffraction component in each first beam L1 that does not diffract towards the fiber 11 side in the second direction can be reduced, and the reduction in coupling efficiency of the first beam L1 coupled to the fiber 11 via the focusing lenses 46 and 47 can be suppressed. Furthermore, in this laser module 20, the fast axis of each second beam L2 incident on the wavelength combining element 45 is parallel to the reference plane SF, which includes all the second planes defined by the second beam L2. Therefore, the spread component of all the second beams L2 in the direction parallel to the reference plane SF is reduced. Thus, the component of each second beam L2 that is not diffracted towards the fiber 11 side in the second direction can be reduced, and the reduction in coupling efficiency of the second beams L2 coupled to the fiber 11 via the focusing lenses 46 and 47 can be suppressed. Therefore, according to this laser module 1, a diffraction grating is used as the wavelength combining element 45, thereby suppressing the reduction in diffraction efficiency, resulting in increased density of emitted light and the emission of high-brightness light.

[0102] Furthermore, in this embodiment, although the expansion component in the slow axis direction of the first light L1 and the second light L2 incident on the wavelength combining element 45 increases, the expansion component in the direction perpendicular to the reference plane SF of the light incident on the wavelength combining element 45 has a smaller impact on the mutual interference of the light emitted from the wavelength combining element 45 compared to the expansion component in the direction parallel to the reference plane SF.

[0103] Furthermore, as described above, in this embodiment, the wavelength combining element 45 is configured such that the total power of the first light L1 reflected by the wavelength combining element 45 and traveling towards the optical fiber 11 along the second direction is 80% or more relative to the total power of the first light L1 incident on the wavelength combining element 45. Additionally, the wavelength combining element 45 is configured such that the total power of the second light L2 emitted from the wavelength combining element 45 and traveling towards the optical fiber 11 along the second direction is 80% or more relative to the total power of the second light L2 incident on the wavelength combining element 45. With this structure, more than 80% of each of the light L1 and L2 incident on the wavelength combining element 45 is emitted towards the optical fiber 11 along the second direction, thus further increasing the density of light emitted from the wavelength combining element 45. However, this 80% or more is not strictly necessary.

[0104] Furthermore, as described above, in this laser module 20, the wavelength of the light emitted from LD31 and 32 is 970 nm or more and 982 nm or less. As described above, ytterbium is added as an active element to the core 5a of the amplifying fiber 5 of the fiber laser device 1 equipped with this laser module 20. One of the peak bands in the absorption spectrum of the light absorbed by this ytterbium is approximately 970 nm or more and 982 nm or less. Therefore, according to this embodiment, the light emitted from the laser module 20 is effectively absorbed by the ytterbium in the amplifying fiber 5.

[0105] Furthermore, as described above, the fiber laser device 1 of this embodiment includes a laser module 20 and an amplifying fiber 5, into which light emitted from the laser module 20 is incident, and an active element that is excited by the light is added to the fiber core 5a. With this structure, the laser module 20 enables the excitation light converging at the peak wavelength of the active element in the amplifying fiber 5 to be of high density and high brightness, thereby improving the absorption efficiency of the excitation light in the amplifying fiber 5.

[0106] Furthermore, in the fiber laser device 1 of this embodiment, as described above, the wavelengths of the first light L1 and the second light L2 are located on the low-wavelength side and the high-wavelength side, respectively, sandwiching the peak wavelength in the absorption spectrum of light absorbed by ytterbium, an active element. For LDs installed in the same laser module, since they are installed in the same laser module, their external environment and driving conditions are approximately the same. Therefore, the wavelength shift direction of the light emitted from each LD tends to be in the same direction, and each tends to shift towards either the long-wavelength side or the short-wavelength side. Therefore, as described above, if the wavelengths of the first light L1 and the second light L2 are located on the low-wavelength side and the high-wavelength side, respectively, when a wavelength shift towards the long-wavelength side occurs in each LD due to temperature changes in the fiber laser device 1, the wavelength of the first light L1 on the low-wavelength side can shift towards the side with increased absorption rate of the active element, and the wavelength of the second light L2 on the high-wavelength side can shift towards the side with decreased absorption rate of the active element. Therefore, when a wavelength shift occurs, the absorption rates of the first light L1 and the second light L2 on the active element can be balanced overall, suppressing state changes in the laser device caused by variations in the absorption efficiency of the excitation light on the active element. Furthermore, it is not necessary for the wavelengths of the first light L1 and the second light L2 to fall between the peak wavelengths of the absorption spectrum of the light absorbed by the active element, ytterbium, and the peak wavelengths on the low-wavelength and high-wavelength sides, respectively.

[0107] Furthermore, in the fiber laser device 1 of this embodiment, as described above, within a certain range of the operating temperature of the fiber laser device, for example, between 0°C and 60°C, the absorptivity of the first light L1 with a wavelength of approximately 975 nm for ytterbium and the absorptivity of the second light L2 with a wavelength of approximately 977 nm for ytterbium are equal. When there is a difference between the absorptivity of the first light L1 for the active element and the absorptivity of the second light L2 for the active element at such temperatures, the difference in absorptivity needs to be considered when designing the amount of active element added, the length of the amplification fiber, etc. On the other hand, as described above, within a certain range of the normal operating temperature of the fiber laser device, if the absorptivity of the first light L1 for the active element and the absorptivity of the second light L2 for the active element are the same, the amount of active element added can be determined based on a single absorptivity, making the design easier. Moreover, within a certain range of the normal operating temperature of the fiber laser device, it is not necessary for the absorptivity of the first light L1 for the active element and the absorptivity of the second light L2 for the active element to be equal.

[0108] Furthermore, in this embodiment, an example of using a diffraction grating as the wavelength synthesis element 45 has been described, but a VBG can also be used.

[0109] (Second Implementation)

[0110] Next, the second embodiment will be described. Unless otherwise specified, the same reference numerals will be used for structural elements that are the same as or equivalent to those in the first embodiment, and repeated descriptions will be omitted.

[0111] In this embodiment of the fiber laser device, except for having a laser module with a structure different from that of the laser module 20 in the first embodiment, it has the same structure as the fiber laser device 1 in the first embodiment. Figure 9 Therefore, with Figure 3 The same viewing angle is used to show the top view of the laser module 20 in this embodiment. For example... Figure 9 As shown, the laser module 20 of this embodiment has the same structure as the laser module 20 of the first embodiment, except for the number and type of optical element groups. Therefore, the following description will focus on the differences between the optical element groups of this embodiment and those of the first embodiment.

[0112] The optical element group of this embodiment includes: multiple LDs, multiple fast-axis collimating lenses 36, multiple slow-axis collimating lenses 37, multiple reflectors 39, three wavelength plates 247, three reflectors 248, three polarization combining elements 249, three optical rotation elements 40, three wavelength stabilizing elements 43, a first wavelength combining element 245, a second wavelength combining element 246, a first condenser lens 46, and a second condenser lens 47. The multiple LDs, collimating lenses 36 and 37, and reflectors 39 are disposed in the stepped portion 23, while the other optical elements are disposed in the flat plate portion 22.

[0113] The plurality of LDs in this embodiment are arranged on the stepped portion 23 in a manner similar to the plurality of LDs in the first embodiment, with the active layer parallel to the mounting surface 21F. However, the number of the plurality of LDs and the wavelength of the light emitted from a portion of the plurality of LDs are different from those of the plurality of LDs in the first embodiment.

[0114] In this embodiment, the plurality of LDs includes: a first LD group 31G, which consists of a plurality of first LDs 31, for example, emitting a first light L1 with a wavelength of approximately 975 nm; a second LD group 32G, which consists of a plurality of second LDs 32, for example, emitting a second light L2 with a wavelength of approximately 976 nm; and a third LD group 33G, which consists of a plurality of third LDs 33, for example, emitting a third light L3 with a wavelength of approximately 977 nm. In this embodiment, the difference between the wavelength of the second light L2 and the wavelength of the first light L1, and the difference between the wavelength of the third light L3 and the wavelength of the second light L2, are both approximately 1 nm and less than 2 nm.

[0115] Each LD group 31G, 32G, and 33G is arranged along the second direction. The LD group closest to fiber 11 is the first LD group 31G, and the LD group furthest from fiber 11 is the third LD group 33G. Each LD group 31G, 32G, and 33G consists of multiple LDs arranged on one side of the second direction and multiple LDs arranged on the other side. Pairs of one LD on one side and one LD on the other side in each LD group 31G, 32G, and 33G are arranged at each level. Thus, each LD on one side emits light towards the LD arranged on the other side of the same level, and each LD on the other side emits light towards the LD arranged on one side of the same level. Here, "one side" in each LD group 31G, 32G, and 33G refers to the side in the second direction closest to fiber 11, and "the other side" refers to the side in the second direction furthest from fiber 11.

[0116] Each of the plurality of LDs is provided with a collimating lens 36, 37 and a reflecting mirror 39. In each LD group 31G, 32G, 33G, the reflecting mirror 39 on one side of the same stage is adjacent to the reflecting mirror 39 on the other side. In addition, in each LD group 31G, 32G, 33G, the reflecting mirror 39 on one side reflects the light emitted from the LD on one side of the same stage toward the plate portion 22 in the third direction, and the reflecting mirror 39 on the other side reflects the light emitted from the LD on the other side of the same stage toward the optical fiber 11 in the third direction.

[0117] The light reflected by the mirrors 39 on both sides is collimated by the collimating lenses 36 and 37. In each LD group 31G, 32G, and 33G, the light reflected by the mirrors 39 on both sides is as follows... Figure 4 Arranged as shown.

[0118] Three wavelength plates 247 are disposed near the boundary between the flat plate portion 22 and the stepped portion 23, and one is arranged in the optical path of the light reflected by the reflector 39 on one side of each LD group 31G, 32G, and 33G. Each wavelength plate 247 is a half-wavelength plate that rotates the polarization direction of the light by 90°. Therefore, the polarization direction of each light emitted from one side of the reflector 39 is rotated by 90° relative to the polarization direction of each light emitted from the other side of the reflector 39 by the wavelength plate 247.

[0119] Three reflectors 248 are arranged in the optical path through which light transmitted from the wavelength plate 247 passes. Furthermore, each reflector 248 has a reflective surface that reflects light propagating towards the fiber 11 side in the third direction to the opposite side of the fiber 11 side in the second direction. Therefore, the light is reflected by reflector 248 and propagates towards the light reflected by reflector 39 on the other side. The slow axis of the light reflected by reflector 248 is parallel to the third direction, and the fast axis is parallel to the first direction.

[0120] Three polarization combining elements 249 are disposed in the optical path of the light reflected by the mirror 39 on the other side, and in the optical path of the light reflected by the mirror 248. The polarization combining element 249 has, for example, a structure in which two right-angle prisms are attached and a dielectric multilayer film is disposed on one of the prisms. It transmits light from one of two beams with polarization directions differing by 90°, and reflects the other beam in a direction differing by 90° from the incident direction. In this embodiment, the light reflected by the mirror 39 on the other side is transmitted, and the light reflected by the mirror 248 is reflected towards the fiber optic 11 in the third direction.

[0121] Thus, the 12 individual first beams L1 are combined by the polarization combining element 249 and propagate towards the fiber 11 in the third direction. The individual first beams L1 emitted from the polarization combining element 249 are as follows: Figure 4 The beams are arranged as shown, with the slow axis parallel to the second direction and the fast axis parallel to the first direction. In this embodiment, the six first beams L1 located on one side and the six first beams L1 located on the other side are superimposed in a one-to-one manner to form a composite beam. Therefore, as shown... Figure 4 As shown, six first beams L1 are arranged. Furthermore, the twelve second beams L2 and third beams L3 are also combined in a one-to-one manner within the other polarized wave synthesizing elements 249, thus achieving the desired effect. Figure 4 As shown, the light beams are arranged in a six-beam configuration. In addition, the second light L2 and the third light L3 emitted from the polarization synthesizer 249 also propagate toward the fiber 11 in the third direction.

[0122] Three optical rotators 40 are disposed on the optical paths of light L1, L2, and L3. In this embodiment, the structure of the optical rotators 40 is substantially the same as that of the optical rotators 40 in the first embodiment. When light L1, L2, and L3 is incident on the corresponding optical rotator 40, it propagates towards the optical fiber 11 in the second direction. Figure 6 As shown, the slow axis of each light L1, L2, L3 emitted from the optical rotator 40 is parallel to the first direction, and the fast axis is parallel to the third direction.

[0123] Three wavelength stabilizing elements 43 are disposed in the optical paths of each of the light beams L1, L2, and L3 emitted from the optical rotator 40. In this embodiment, each wavelength stabilizing element 43 has a structure substantially the same as that of the wavelength stabilizing element 43 in the first embodiment. Propagating from each wavelength stabilizing element 43 toward the optical fiber 11 in the second direction are: a first light L1 with a wavelength substantially stabilized at 975 nm, a second light L2 with a wavelength substantially stabilized at 976 nm, and a third light L3 with a wavelength substantially stabilized at 977 nm.

[0124] Reflector 44A1 of a pair of mirrors 44A1 and 44A2 is positioned in the optical path of each first light L1 emitted from the wavelength stabilizing element 43 and reflects each first light L1 toward mirror 44A2. Mirror 44A2 reflects the first light L1 reflected by mirror 44A1 toward the first wavelength combining element 245. Thus, the first light L1 reflected by mirror 44A2 is incident on the first wavelength combining element 245. Therefore, mirror 44A2 is an optical element that allows the first light L1 to directly incident on the first wavelength combining element 245. Additionally, mirror 44B1 of a pair of mirrors 44B1 and 44B2 is positioned in the optical path of each second light L2 emitted from the wavelength stabilizing element 43 and reflects each second light L2 toward mirror 44B2. Mirror 44B2 reflects the second light L2 reflected by mirror 44B1 toward the second wavelength combining element 246. In this way, the second light L2 reflected by the reflector 44B2 is incident on the second wavelength combining element 246. Therefore, the reflector 44B2 is an optical element that allows the second light L2 to be directly incident on the second wavelength combining element 246.

[0125] The second wavelength combining element 246 is disposed in the optical path of each third light L3 emitted from the wavelength stabilizing element 43, and in the optical path of each second light L2 reflected by the reflector 44B2. Therefore, the wavelength stabilizing element 43 through which the third light L3 is transmitted is an optical element that allows the third light L3 to be directly incident on the second wavelength combining element 246. The second wavelength combining element 246 is a VBG that reflects each second light L2 under specified conditions and allows each third light L3 to pass through and be emitted. The second wavelength combining element 246 is tilted at a specified angle relative to the second direction and the third direction. The tilt angle of the second wavelength combining element 246 is such that the incident angle of the third light L3 incident on the second wavelength combining element 246 is a first incident angle, and is such that the incident angle of the second light L2 incident on the second wavelength combining element 246 is a second incident angle different from the first incident angle. In the second wavelength combining element 246, a periodic refractive index change is formed such that when the second light L2 is incident at a second incident angle and the third light L3 is incident at a first incident angle, the light L2 and L3 are emitted in approximately the same predetermined direction. In this embodiment, the predetermined direction is the direction on the fiber 11 side in the second direction. Therefore, each second light L2 incident on the second wavelength combining element 246 is reflected by the second wavelength combining element 246 and emitted towards the fiber 11. Furthermore, each third light L3 incident on the second wavelength combining element 246 is transmitted through the second wavelength combining element 246 and coincides with each second light L2 in a one-to-one manner, emitting towards the fiber 11 side. This forms a plurality of combined light SL2s that propagate towards the first wavelength combining element 245. Therefore, the first wavelength combining element 245 is an optical element from which the second light L2 and the third light L3 emitted from the second wavelength combining element 246 are directly incident.

[0126] Here, the overlapping second light L2 and third light L3 in each second light L2 and each third light L3 are paired. In each pair, a first plane is defined. This first plane passes through the entire interval from the optical element (mirror 44B2) through which the second light L2 is directly incident on the second wavelength combining element 246 to the optical axis of the second light L2 of the second wavelength combining element 246, and the entire interval from the second wavelength combining element 246 to the optical element (first wavelength combining element 245) through which the second light L2 emitted from the second wavelength combining element 246 is directly incident. This first plane is defined according to each second light L2. In this embodiment, each first plane defined according to each second light L2 can be made parallel to the mounting surface 21F. At this time, the fast axis of each second light L2 incident on the second wavelength combining element 246 is parallel to the first plane in the above pair. In addition, in this embodiment, the height of the optical axis of each second light L2 incident on the second wavelength combining element 246 is consistent, so the height of each first plane can be made the same. Therefore, in this embodiment, each first plane can be contained within a reference plane that is mutually repeated.

[0127] Furthermore, in each of the above pairs, a second plane is defined, which passes through the entire range of the optical axis of the second light L2 from the reflector 44B2 to the second wavelength combining element 246, and the entire range of the optical axis of the second light L2 from the second wavelength combining element 246 to the first wavelength combining element 245. This second plane is defined according to each third light L3. In this embodiment, each second plane defined according to each third light L3 can be made parallel to the mounting surface 21F. In addition, in this embodiment, the height of the optical axis of each third light L3 incident on the second wavelength combining element 246 is the same as the height of the optical axis of each second light L2 incident on the second wavelength combining element 246, and the height of the optical axis of each third light L3 reflected by the second wavelength combining element 246 is the same as the height of the optical axis of each second light L2 reflected by the second wavelength combining element 246. Therefore, the height of each second plane can be the same as the height of the first plane. Therefore, in this embodiment, each second plane can be included in the above-mentioned reference plane SF.

[0128] The first wavelength combining element 245 is disposed in the optical path of each combining light SL2, and in the optical path of each first light L1 reflected by the reflector 44A2. Each combining light SL2 emitted from the second wavelength combining element 246 is incident on the first wavelength combining element 245. Therefore, the second wavelength combining element 246, which emits the combining light SL2, is an optical element that allows the second light L2 and the third light L3 to be directly incident on the first wavelength combining element 245. In this embodiment, the first wavelength combining element 245 is a VBG that reflects the first light L1 under predetermined conditions and allows the second light L2 and the third light L3 forming the combining light SL2 to pass through and be emitted. The first wavelength combining element 245 is tilted at a predetermined angle relative to the second direction and the third direction. The tilt angle of the first wavelength combining element 245 is such that the angle of incidence of the first light L1 incident on the first wavelength combining element 245 is a third angle of incidence, and the angle of incidence of the second light L2 and the third light L3 incident on the first wavelength combining element 245 is a fourth angle of incidence different from the third angle of incidence. In the first wavelength combining element 245, a periodic refractive index change is formed such that when the first light L1 is incident at the third angle of incidence, and the second light L2 and the third light L3 are incident at the fourth angle of incidence, the first light L1, the second light L2, and the third light L3 are emitted in approximately the same predetermined direction. In this embodiment, the predetermined direction is the direction on the fiber optic 11 side in the second direction. Therefore, each first light L1 incident on the first wavelength combining element 245 is reflected by the first wavelength combining element 245 and emitted towards the first focusing lens 46. Furthermore, each of the second light L2 and third light L3 incident on the first wavelength combining element 245 is transmitted through the first wavelength combining element 245 and coincides with the first light L1 in a one-to-one manner, forming multiple composite light SL1 composed of one first light L1, one second light L2, and one third light L3. These composite light SL1 propagate toward the first condenser lens 46. Therefore, the first condenser lens 46 is an optical element in which the first light L1, second light L2, and third light L3 emitted from the first wavelength combining element 245 are directly incident.

[0129] Here, the overlapping first light L1 and second light L2 in each first light L1 and each second light L2 are paired. In each pair, a first plane is defined. This first plane passes through the entire range from the optical element (mirror 44A2) that causes the first light L1 to directly enter the first wavelength combining element 245 to the optical axis of the first light L1 in the first wavelength combining element 245, and the entire range from the first wavelength combining element 245 to the optical element (first condenser lens 46) that directly enters the first light L1 emitted from the first wavelength combining element 245. This first plane is defined according to each first light L1. In this embodiment, each first plane defined according to each first light L1 can be made parallel to the mounting surface 21F. At this time, the fast axis of each first light L1 incident on the first wavelength combining element 245 is parallel to the first plane in each of the above pairs. In addition, in this embodiment, the height of the optical axis of each first light L1 incident on the first wavelength combining element 245 is consistent, which makes the height of each first plane the same. Therefore, in this embodiment, each first plane can be contained within a reference plane that is mutually repeated.

[0130] Furthermore, in each of the above pairs, a second plane is defined, which passes through the entire range of the optical axis of the first light L1 from the reflector 44A2 to the first wavelength combining element 245, and the entire range of the optical axis of the first light L1 from the first wavelength combining element 245 to the first condenser lens 46. This second plane is defined according to each second light L2. In this embodiment, each second plane defined according to each second light L2 can be made parallel to the mounting surface 21F. In addition, in this embodiment, the height of the optical axis of each second light L2 incident on the first wavelength combining element 245 is the same as the height of the optical axis of each first light L1 incident on the first wavelength combining element 245, and the height of the optical axis of each second light L2 transmitted through the first wavelength combining element 245 is the same as the height of the optical axis of each first light L1 reflected from the first wavelength combining element 245. Therefore, the height of each second plane can be the same as the height of the first plane. Therefore, in this embodiment, each second plane can be included in the above-mentioned reference plane SF.

[0131] Furthermore, the second plane is determined from another perspective. Specifically, the overlapping first light L1 and third light L3 in each first light L1 and each third light L3 are paired, and in each pair, a second plane is determined that passes through the entire range of the optical axis of the first light L1 from the reflector 44A2 to the first wavelength combining element 245, and the entire range of the optical axis of the first light L1 from the first wavelength combining element 245 to the first condenser lens 46. This second plane is the plane determined according to each third light L3. In this embodiment, each second plane determined according to each third light L3 can be made parallel to the mounting surface 21F. In addition, in this embodiment, the height of the optical axis of each third light L3 incident on the first wavelength combining element 245 is the same as the height of the optical axis of each first light L1 incident on the first wavelength combining element 245, and the height of the optical axis of each third light L3 transmitted through the first wavelength combining element 245 is the same as the height of the optical axis of each first light L1 reflected from the first wavelength combining element 245. Therefore, the height of each second plane can be the same as the height of the first plane. Therefore, in this embodiment, each second plane can be included in the aforementioned reference plane SF.

[0132] Each synthesized light SL1 emitted from the first wavelength synthesizing element 245 is incident on the first condensing lens 46, then on the second condensing lens 47, where it is focused in both the fast and slow axis directions and incident on the core of the optical fiber 11.

[0133] The synthesized light SL1 excites ytterbium added to the core 5a of the amplifying fiber 5. For example... Figure 8 As shown, the absorption rates of ytterbium for light with a peak wavelength of approximately 976 nm and a lower wavelength of approximately 975 nm in the absorption spectrum containing ytterbium are equal to those for light with a higher wavelength of approximately 977 nm. In this embodiment, such light with a wavelength of approximately 975 nm, approximately 976 nm, and approximately 977 nm are used as excitation light.

[0134] As described above, in the laser module 20 of this embodiment, the fast axis of each second beam L2 incident on the second wavelength combining element 246 is parallel to a reference plane including a first plane defined according to the second beam L2. Therefore, the expansion component of the second beam L2 in the direction parallel to the reference plane is less than when the slow axis of the second beam L2 is parallel to the reference plane. Therefore, the component of each second beam L2 that does not diffract towards the first wavelength combining element 245 in the second direction can be reduced. Furthermore, in this laser module 20, the fast axis of each third beam L3 incident on the second wavelength combining element 246 is parallel to a reference plane including a second plane defined according to the third beam L3. Therefore, the expansion component of the third beam L3 in the direction parallel to the reference plane is less. Therefore, the component of each third beam L3 that does not diffract towards the first wavelength combining element 245 in the second direction can be reduced.

[0135] Furthermore, in this embodiment, when the second light L2 reflected by the second wavelength combining element 246 is renamed as the first light L2 and the third light L3 transmitted through the second wavelength combining element 246 is renamed as the second light L3, the second wavelength combining element 246 reflects each of the first lights L2 in a predetermined direction, and makes each of the second lights L3 coincide with each of the first lights L2 in a one-to-one manner, and emits them in a predetermined direction. In each pair of the overlapping first lights L2 and second lights L3, the fast axis of the first light L2 incident on the second wavelength combining element 246 is parallel to the first plane in the pair, and the fast axis of the second light L3 incident on the second wavelength combining element 246 is parallel to the second plane in the pair.

[0136] Furthermore, in the laser module 20 of this embodiment, the fast axis of each first beam L1 incident on the first wavelength combining element 245 is parallel to a reference plane including a first plane defined according to the first beam L1. Therefore, the spread component of the first beam L1 in the direction parallel to the reference plane is less than when the slow axis of the first beam L1 is parallel to the reference plane. Therefore, the component of each first beam L1 that does not diffract towards the fiber 11 side in the second direction can be reduced. Additionally, in this laser module, the fast axis of each second beam L2 incident on the first wavelength combining element 245 is parallel to a reference plane including a second plane defined according to the second beam L2. Therefore, the spread component of the second beam L2 in the direction parallel to the reference plane is less. Therefore, the component of each second beam L2 that does not diffract towards the first condenser lens 46 side in the second direction can be reduced. Furthermore, in this laser module 20, the fast axis of each third beam L3 incident on the first wavelength combining element 245 is parallel to a reference plane including a second plane defined according to the third beam L3. Therefore, the expansion component of the third beam L3 in the direction parallel to the reference plane is reduced. Consequently, the component of each third beam L3 that does not diffract towards the first focusing lens 46 in the second direction is reduced. Therefore, according to the laser module 20 of this embodiment, by synthesizing beams L1, L2, and L3 while suppressing the reduction in diffraction efficiency, the light density can be increased and high-brightness light can be emitted.

[0137] Furthermore, similar to the first embodiment, although the spread component in the slow axis direction of the first, second, and third light incident on the wavelength combining element increases, the spread component in the direction perpendicular to the reference plane has a smaller impact on the interference between the light emitted from the wavelength combining element compared to the spread component in the direction parallel to the reference plane. Therefore, as described above, by reducing the spread component of the light parallel to the reference plane, it is possible to suppress the reduction in diffraction efficiency in the wavelength combining element.

[0138] Furthermore, unlike the first embodiment, this embodiment has three LD groups, and the number of LDs constituting each LD group is a multiple of the number of LDs constituting the LD group in the first embodiment. Therefore, the light density can be further increased, and high-brightness light can be generated with higher output.

[0139] Furthermore, this embodiment illustrates an example where a first wavelength combining element 245 is provided to combine light L1, L2, and L3; and a second wavelength combining element 246 is provided to combine light L2 and L3, and all light L1, L2, and L3 are combined. However, it is sufficient to combine at least two of light L1, L2, and L3. For example, only the first wavelength combining element 245 may be provided, and only light L1 and L2 may be combined. Alternatively, only the second wavelength combining element 246 may be provided, and only light L2 and L3 may be combined.

[0140] Furthermore, although this embodiment describes wavelength synthesis elements 245 and 246 as examples of VBGs, at least one of them may also be a diffraction grating.

[0141] Furthermore, the first to fourth incident angles can be, for example, 3° or more and less than 90°, or 3° or more and less than 45°. Additionally, each wavelength combining element 245, 246 can be configured such that the total power of the light emitted from the wavelength combining element is 80% or more relative to the total power of the light incident on the wavelength combining element.

[0142] Although the present invention has been described using the above embodiments as examples, the present invention is not limited thereto.

[0143] For example, although the above embodiments illustrate examples of two or three different wavelengths of light, a fourth LD group emitting a fourth wavelength of light can also be provided, so that there are four types of different wavelengths of light. This allows for four or more types of light. Furthermore, as explained in the second embodiment, even if there are four or more types of light, it is sufficient to combine at least two different wavelengths of light.

[0144] Furthermore, although the above embodiments illustrate the use of ytterbium as an active element, the active element is not limited to ytterbium. Additionally, when ytterbium is not used and other elements are employed as the active element, it is preferable that the wavelength of the light emitted by the LD is the wavelength of the peak band in the absorption spectrum of the light absorbed by that active element.

[0145] Furthermore, although the above embodiment illustrates an example where the wavelength interval between the Nth light and the (N+1)th light (where N is 1 or more) is less than 2 nm, this interval can also be 2 nm or more. It should be noted that if this interval is less than 2 nm, even in the case of a narrow peak band as described above, it is easy to converge all wavelengths of light into that peak band.

[0146] Furthermore, when a VBG is used as a wavelength combining element, the wavelength combining element can be an apodized VBG. With this structure, when sidelobes are generated in the distribution of the VBG's diffraction efficiency relative to the wavelength of light incident on the VBG, these sidelobes can be reduced. As a result, even for light with short wavelength intervals, combining can be performed without interference from sidelobes.

[0147] Furthermore, in the above embodiment, an example was described where each first plane is contained within a reference plane SF parallel to the mounting surface 21F. However, each first plane is not necessarily contained within a reference plane. This will be explained below.

[0148] For example, such as Figure 10 As shown, the fast axis of the first light L1a is parallel to the fast axis of the first light L1b, but the case where the first light L1a and the first light L1b are offset along the first direction is also considered. In this case, the optical axis LA1a of the first light L1a and the optical axis LA1b of the first light L1b are not at the same height. Therefore, the reference plane SF1a determined by the optical axis LA1a of the first light L1a and the first plane SF1b determined by the optical axis LA1b of the first light L1b are different planes. Furthermore, in Figure 10 The image shows only a portion of the reference plane SF1a and the first plane SF1b.

[0149] In addition, such as Figure 11 As shown, consider the case where the fast axis of the first beam L1a is not parallel to the fast axis of the first beam L1b. In this case, the first plane SF1b, defined by the first beam L1b, is inclined relative to the reference plane SF1a. Figure 11 In the example, the reference plane SF1a is the plane defined by the optical axis LA1a of the first light L1a. Furthermore, in Figure 11The diagram shows only a portion of the reference plane SF1a and the first plane SF1b. In this case, the first plane SF1b is a plane different from the reference plane SF1a and does not pass through the optical axis LA1b of the first light L1b. It should be noted that the first plane SF1b needs to pass through the entire range from the optical element that causes the first light L1b to be directly incident on the wavelength combining element 45 to the first light L1b of the wavelength combining element 45, and the entire range from the wavelength combining element 45 to the optical element from which the first light L1b emitted from the wavelength combining element 45 is directly incident. Based on this condition, even when the first plane SF1b is tilted relative to the reference plane SF1a, the tilt angle of the first plane SF1b relative to the reference plane SF1a is small, and the tilt angle of the fast axis of the first light L1b that determines the first plane SF1b relative to the reference plane SF1a is also small. Therefore, even when the fast axis of the first light L1b is tilted, the spread component of the first light L1b in the direction parallel to the reference plane SF1a can be reduced. It should be noted that, from the perspective of suppressing the reduction of diffraction efficiency, it is preferable that the first plane passes through the optical axis of the first light.

[0150] Furthermore, in the above embodiment, an example was described where each second plane is contained within a reference plane SF parallel to the mounting surface 21F. However, compared to... Figure 10 Similarly, the fast axis of one second beam L2 is parallel to the fast axis of the other second beam L2, but it is also possible that one second beam L2 and the other second beam L2 are offset along the first direction. In this case, the height of the optical axis of one second beam is not the same as the height of the optical axis of the other second beam, and the second plane determined by the optical axis of one second beam L2 and the second plane determined by the optical axis of the other second beam are different planes.

[0151] In addition, such as Figure 12 As shown, consider the case where the fast axis of the second beam L2 is not parallel to the fast axis of the first beam L1. In this case, the second plane SF2, defined by the second beam L2, is tilted relative to the reference plane SF1, defined by the optical axis LA1 of the first beam L1. Furthermore, in Figure 12 In the diagram, only a portion of the reference plane SF1 and the second plane SF2 are shown. Additionally, one instance of the first beam L1 and one instance of the second beam L2 are also shown. Figure 12In the example, the second plane SF2 defined by the second beam L2 is a plane different from the reference plane SF1 defined by the first beam L1, and does not pass through the optical axis LA2 of the second beam L2. It should be noted that the second plane SF2 needs to pass through the entire interval from the optical element through which the first beam L1 is directly incident on the wavelength combining element 45 to the first beam L1 of the wavelength combining element 45, and the entire interval from the wavelength combining element 45 to the optical element through which the first beam L1 emitted from the wavelength combining element 45 is directly incident. Based on this condition, even when the second plane SF2 is tilted relative to the reference plane SF1, the tilt angle of the second plane SF2 relative to the reference plane SF1 is small, and the tilt angle of the fast axis of the second beam L2 defining the second plane SF2 relative to the reference plane SF1 is also small. Therefore, even when the fast axis of the second beam L2 is tilted, the spread component of the second beam L2 in the direction parallel to the reference plane SF1 can be reduced. It should be noted that, from the viewpoint of suppressing the reduction in diffraction efficiency, it is preferable that the second plane SF2 passes through the optical axis LA1 of the first beam L1. Furthermore, although in Figure 12 The example illustrates a wavelength combining element that is a diffraction grating, but the same applies when the wavelength combining element is a VBG.

[0152] However, it is preferable that the fast axes of each first light L1 incident on the wavelength combining element 45 are parallel to each other. This allows the first light L1s to be brought closer together, resulting in a higher density of first light L1 incident on the wavelength combining element 45, compared to when at least a portion of the fast axes of the first light L1s incident on the wavelength combining element 45 are not parallel. Therefore, higher brightness light can be emitted. Furthermore, it is preferable that the fast axes of each second light L2 incident on the wavelength combining element 45 are parallel to the fast axis of at least one first light L1. This increases the degree of overlap between the first light L1 and the second light L2, and increases the density of the first light L1 and the second light L2 incident on the wavelength combining element 45, compared to when the fast axes of the second light L2 are not parallel to the fast axes of the first light L1. Therefore, higher brightness light can be emitted. Furthermore, it is preferable that the fast axes of the second light L2 incident on the wavelength combining element 45 are parallel to each other. Therefore, compared to when at least a portion of the fast axes of the second beams L2 incident on the wavelength combining element 45 are not parallel to each other, it is possible to bring the second beams L2 closer together, resulting in a high density of second beams L2 incident on the wavelength combining element. Thus, it is possible to emit light with higher brightness.

[0153] Furthermore, in the above embodiments, an example was described in which light incident on the wavelength combining element propagates in a direction parallel to the mounting surface; however, the direction of light emitted from the wavelength combining element is not limited to this direction.

[0154] According to the present invention, a laser module capable of emitting high-brightness light and a fiber laser device incorporating the laser module can be provided, which can be used in fields such as laser processing.

Claims

1. A laser module, characterized by, Possessing: a first laser diode that emits first light; a second laser diode that emits second light different in wavelength from the first light; a fast axis collimation lens that is provided corresponding to each of the first laser diode and the second laser diode, and collimates a fast axis direction of light emitted from each of the first laser diode and the second laser diode; a slow axis collimation lens that is provided corresponding to each of the first laser diode and the second laser diode, and collimates a slow axis direction of light emitted from each of the first laser diode and the second laser diode; and a wavelength combining element composed of a VBG (Volume Bragg Grating) or a diffraction grating, the first light emitted from the first laser diode and transmitted through the fast axis collimation lens and the slow axis collimation lens, and the second light emitted from the second laser diode and transmitted through the fast axis collimation lens and the slow axis collimation lens are incident on the wavelength combining element, the wavelength combining element reflects the first light in a prescribed direction, and superimposes the second light on the first light and emits it in the prescribed direction, a fast axis of the first light incident on the wavelength combining element is parallel to a first plane that passes through an entire range of the first light from an optical element that makes the first light directly incident on the wavelength combining element to the wavelength combining element, and an entire range of the first light from the wavelength combining element to an optical element on which the first light emitted from the wavelength combining element is directly incident, a fast axis of the second light incident on the wavelength combining element is parallel to a second plane that passes through an entire range of the first light from an optical element that makes the first light directly incident on the wavelength combining element to the wavelength combining element, and an entire range of the first light from the wavelength combining element to an optical element on which the first light emitted from the wavelength combining element is directly incident, the first laser diode, the second laser diode, and the wavelength combining element are mounted on mounting surfaces that are parallel to each other, the first plane passes through an optical axis of the first light incident on the wavelength combining element and an optical axis of the first light reflected at the wavelength combining element, and is parallel to the mounting surfaces.

2. The laser module according to claim 1, wherein the second plane passes through an optical axis of the first light incident on the wavelength combining element and an optical axis of the first light reflected at the wavelength combining element.

3. The laser module according to claim 1 or 2, wherein a plurality of the first laser diodes and a plurality of the second laser diodes are provided, each of the first light emitted from the plurality of the first laser diodes and each of the second light emitted from the plurality of the second laser diodes is transmitted through the fast axis collimation lens and the slow axis collimation lens and is incident on the wavelength combining element, The wavelength-combining element reflects each of the first lights in the prescribed direction and causes each of the second lights to coincide with each of the first lights in a one-to-one manner and to be emitted in the prescribed direction, In each of the pairs of the first light and the second light that overlap with each other, a fast axis of the first light incident on the wavelength-combining element is parallel to the first plane in the pair, and a fast axis of the second light incident on the wavelength-combining element is parallel to the second plane in the pair.

4. The laser module according to claim 3, wherein Fast axes of each of the first lights incident on the wavelength-combining element are parallel to each other.

5. The laser module according to claim 3, wherein A fast axis of each of the second lights incident on the wavelength-combining element is parallel to a fast axis of at least one of the first lights.

6. The laser module according to claim 3, wherein Fast axes of each of the second lights incident on the wavelength-combining element are parallel to each other.

7. The laser module according to claim 1 or 2, wherein Wavelengths of the lights emitted from the first laser diode and the second laser diode are 970 nm or more and 982 nm or less.

8. The laser module according to claim 7, wherein The wavelength of the first light and the wavelength of the second light sandwich 976 nm, and a difference between the wavelength of the first light and the wavelength of the second light is within 2 nm.

9. The laser module according to claim 1 or 2, wherein Incidence angles of the first light with respect to the wavelength-combining element and incidence angles of the second light with respect to the wavelength-combining element are each 3° or more.

10. The laser module according to claim 1 or 2, wherein The wavelength-combining element is a VBG having apodization.

11. The laser module according to claim 1 or 2, wherein An entire power of the first light reflected by the wavelength-combining element and traveling in the prescribed direction is 80% or more with respect to an entire power of the first light incident on the wavelength-combining element, and an entire power of the second light emitted from the wavelength-combining element and traveling in the prescribed direction is 80% or more with respect to an entire power of the second light incident on the wavelength-combining element.

12. A fiber laser device, comprising: comprises: the laser module according to any one of claims 1 to 11; and an amplification optical fiber that emits the light emitted from the laser module and in which an active element that is excited by the light is added in a core.

13. The fiber laser device according to claim 12, wherein The wavelength of the first light and the wavelength of the second light are on a low-wavelength side and a high-wavelength side of a peak wavelength in an absorption spectrum of light absorbed by the active element.

14. The fiber laser device according to claim 13, wherein In a part of a use temperature of the fiber laser device, an absorption rate of the first light with respect to the active element and an absorption rate of the second light with respect to the active element are equal to each other.

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