Semiconductor laser module, light source device, and optical fiber laser

Abstract

This semiconductor laser module is provided with, for example: a plurality of semiconductor laser elements; an optical fiber; a first optical component that arranges light beams output from the plurality of semiconductor laser elements at intervals in the fast-axis direction; a reflection mirror that reflects a specific wavelength band component of the light beams output from the semiconductor laser elements and arranged at intervals in the fast-axis direction, and constitutes an external resonator with the plurality of semiconductor laser elements; an aperture that is provided in the external resonator and limits the width in the slow-axis direction of multimode laser light so as to remove a high-order mode component of the laser light from the light beams arranged at intervals in the fast-axis direction; and a condenser lens that couples laser light output from the external resonator to an output optical fiber.

Description

Semiconductor laser module, light source device, and optical fiber laser

[0001] The present invention relates to a semiconductor laser module, a light source device, and an optical fiber laser.

[0002] 2. Description of the Related Art Conventionally, a semiconductor laser module is known in which laser light output from a plurality of light-emitting elements is guided to an end of an optical fiber via a plurality of optical components (see, for example, Patent Document 1).

[0003] International Publication No. 2019 / 160038

[0004] It would be beneficial if this type of semiconductor laser module could output laser light in a desired wavelength band and consume little unnecessary energy.

[0005] Therefore, one object of the present invention is to provide an improved new semiconductor laser module, light source device, and optical fiber laser that can output laser light in a desired wavelength band and reduce unnecessary energy consumption, for example.

[0006] A semiconductor laser module of the present invention includes, for example, a plurality of semiconductor laser elements each outputting multimode laser light as laser light and having substantially the same fast-axis direction and slow-axis direction; a first optical component arranging the laser light output from the plurality of semiconductor laser elements at intervals in the fast-axis direction; a reflection mirror that reflects components of a specific wavelength band from the light output from the semiconductor laser elements and arranged at intervals in the fast-axis direction, and forms an external resonator between the reflection mirror and the plurality of semiconductor laser elements; an aperture provided within the external resonator that limits the width of the laser light in the slow-axis direction so as to remove higher-order mode components of the multimode laser light from the laser light arranged at intervals in the fast-axis direction; and a focusing lens that couples the laser light output from the external resonator to an output optical fiber.

[0007] In the semiconductor laser module, the aperture may be located between the reflecting mirror and the first optical component.

[0008] In the semiconductor laser module, the semiconductor laser element may have a front surface reflectance of 2% or less.

[0009] In the semiconductor laser module, the semiconductor laser element may have a front surface reflectance of 0.5% or less.

[0010] In the semiconductor laser module, the reflectance of the reflecting mirror may be 4% or more.

[0011] In the semiconductor laser module, the aperture and the reflecting mirror may be spaced apart.

[0012] In the semiconductor laser module, the aperture and the reflecting mirror may be integrated.

[0013] In the semiconductor laser module, the focusing lens may include a first lens as an aspherical lens that focuses the plurality of parallel laser beams dispersed in the fast axis direction onto a convergence point at an end of the output optical fiber, and the reflecting mirror may reflect the plurality of parallel laser beams to the plurality of semiconductor laser elements.

[0014] A light source device of the present invention includes, for example, the semiconductor laser module.

[0015] The optical fiber laser of the present invention includes, for example, the light source device, an amplification optical fiber, and an optical component that guides the laser light output from the light source device to the amplification optical fiber.

[0016] In the optical fiber laser, the reflecting mirror may reflect components of a wavelength band that includes, at its center, a wavelength at which the absorption spectrum of the Yb-doped double-clad fiber is high.

[0017] According to the present invention, it is possible to obtain a semiconductor laser module, a light source device, and an optical fiber laser having a more improved and novel configuration.

[0018] FIG. 1 is an exemplary and schematic plan view of a semiconductor laser module according to a first embodiment. FIG. 2 is an exemplary and schematic perspective view of the semiconductor laser module according to the first embodiment. FIG. 3 is a graph showing an example of the absorptance as a function of wavelength of a Yb-doped double-clad fiber included in an optical fiber laser. FIG. 4 is an exemplary and schematic perspective view of an aperture included in the semiconductor laser module according to the first embodiment. FIG. 5 is an exemplary and schematic plan view of an enlarged portion of the semiconductor laser module according to the first embodiment. FIG. 6 is a graph showing an example of the relationship between the coupling efficiency of light emitted from a semiconductor laser element of the semiconductor laser module according to the first embodiment to a reflecting mirror and the threshold carrier density as the amount of current required for laser oscillation of the semiconductor laser module. FIG. 7 is a graph showing an example of the relationship between slope efficiency and front surface reflectivity of a semiconductor laser element in the semiconductor laser module according to the first embodiment. FIG. 8 is an exemplary and schematic perspective view of an aperture included in a semiconductor laser module according to a second embodiment. FIG. 9 is an exemplary and schematic plan view of a portion of a semiconductor laser module according to a third embodiment. Fig. 10 is an exemplary schematic diagram showing a plurality of laser elements, a reflecting mirror, and two condenser lenses of a semiconductor laser module according to a fourth embodiment, as viewed in the slow axis direction. Fig. 11 is an exemplary schematic diagram showing a reflecting mirror and two condenser lenses of a semiconductor laser module according to a reference example, as viewed in the slow axis direction. Fig. 12 is an exemplary schematic diagram of an optical fiber laser according to a fifth embodiment.

[0019] Exemplary embodiments of the present invention are disclosed below. The configurations of the embodiments described below, as well as the actions and results (effects) brought about by the configurations, are merely examples. The present invention can also be realized by configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derivative effects) obtained by the configurations.

[0020] The following embodiments have similar configurations. Therefore, according to the configurations of each embodiment, similar actions and effects based on the similar configurations can be obtained. Furthermore, in the following, similar configurations are given similar reference numerals, and duplicated descriptions may be omitted.

[0021] In this specification, ordinal numbers may be assigned for convenience to distinguish between parts, members, parts, directions, lights, etc. Note that ordinal numbers do not indicate priority or order, nor do they specify a number.

[0022] In each drawing, the X direction is represented by an arrow X, the Y direction is represented by an arrow Y, and the Z direction is represented by an arrow Z. The X direction, Y direction, and Z direction intersect with each other and are perpendicular to each other. The direction behind the arrow X is referred to as the opposite direction to the X direction, the direction behind the arrow Y is referred to as the opposite direction to the Y direction, and the direction behind the arrow Z is referred to as the opposite direction to the Z direction. Furthermore, each drawing is a schematic diagram, and the shape, dimensions, ratios, etc. of each part may differ from the actual ones.

[0023] 1 is a plan view of a semiconductor laser module 10 according to a first embodiment, and FIG. 2 is a perspective view of the semiconductor laser module 10.

[0024] The semiconductor laser module 10 includes a base 24 , a plurality of semiconductor laser elements 12 , an optical system 14 provided corresponding to each of the semiconductor laser elements 12 , an output section 18 , and a terminal section 20 .

[0025] The output section 18 supports an optical fiber 68 that transmits output light. The terminal section 20 is a connection terminal to which a conductor of a wiring that supplies power from an external power source to the semiconductor laser element 12 is electrically connected. The optical fiber 68 is an example of an output optical fiber.

[0026] 1 and 2, the base 24 supports each component included in the semiconductor laser module 10. The base 24 can also be called a support member or a mounted member.

[0027] 2, the base 24 has a stepped portion 38. The stepped portion 38 has a plurality of step surfaces 40 that are shifted at equal intervals in the Z direction as they move in the opposite direction to the Y direction. The step surfaces 40 are substantially flat, all facing the Z direction, and intersect with and are perpendicular to the Z direction.

[0028] A semiconductor laser element 12 with the same specifications is mounted on each step surface 40. The multiple semiconductor laser elements 12 all output laser light whose fast axis direction is in the Z direction and the direction opposite to the Z direction, and whose slow axis direction is in the Y direction and the direction opposite to the Y direction. In other words, the fast axis directions of the multiple semiconductor laser elements 12 are substantially the same, and the slow axis directions are substantially the same. Furthermore, in this embodiment, all of the semiconductor laser elements 12 output multimode laser light as laser light. Note that in this embodiment, the semiconductor laser element 12 is mounted on a submount 42 to form a chip-on-submount, but this is not limiting and the semiconductor laser element 12 may be housed in a case and unitized, for example.

[0029] In addition, collimating lenses 58 and 60 and a mirror 62 are mounted on each step surface 40. On each step surface 40, the laser light output from the semiconductor laser element 12 travels in the X direction, is first collimated in the fast axis direction by the collimating lens 58, is then collimated in the slow axis direction by the collimating lens 60, and travels to the mirror 62.

[0030] The mirrors 62 each reflect the laser light traveling in the X direction and direct it in the Y direction. When the laser light is reflected by the mirrors 62, the fast axis direction does not change, but the slow axis direction changes from the Y direction and the opposite direction to the X direction and the opposite direction to the X direction.

[0031] The laser light reflected by each mirror 62 and traveling in the Y direction is coupled to the end of the optical fiber 68 via the aperture 111, the reflecting mirror 511, and the condenser lenses 64 and 65. The condenser lens 64 converges the laser light in the fast axis direction (the Z direction and the direction opposite to the Z direction), and the condenser lens 65 converges the laser light in the slow axis direction (the X direction and the direction opposite to the X direction). The reflecting mirror 511 and the aperture 111 will be described in detail later.

[0032] In the above-described configuration, the multiple step surfaces 40 are offset at a predetermined interval in the Z direction, in other words, their positions in the Z direction are different, so that the multiple laser beams reflected by the mirror 62 and traveling in the Y direction are aligned at intervals in the Z direction before being input to the reflecting mirror 511. In other words, the step portion 38 (step surfaces 40), the multiple semiconductor laser elements 12, the collimating lenses 58 and 60, and the mirror 62 are arranged so that the multiple laser beams input to the reflecting mirror 511 are aligned at intervals in the Z direction. In this embodiment, the collimating lenses 58 and 60 and the mirror 62 interposed between the semiconductor laser elements 12 and the reflecting mirror 511 are referred to as the optical system 14. Each optical component included in the optical system 14 is an example of a first optical component. 1 and 2, any configuration may be used as long as it allows the multiple laser beams input to the reflecting mirror 511 to be aligned at intervals in the Z direction. The semiconductor laser module 10 may include multiple parallel configurations including the step portion 38, the step surface 40, and the optical system 14, and the multiple laser beams input to the reflecting mirror 511 from these multiple configurations may be aligned at intervals in the Z direction. The alignment of multiple laser beams at intervals means that the optical axes of the multiple laser beams are aligned at intervals.

[0033] 3 is a graph showing an example of the absorptance as a function of wavelength of a Yb-doped double-clad fiber included in an optical fiber laser. When the semiconductor laser module 10 mainly outputs laser light containing components in a wavelength band B (λc±3 nm) with a center wavelength λc of 976 nm, for example, as shown in FIG. 3 , the output efficiency of an optical fiber laser including the Yb-doped double-clad fiber as an amplification fiber and using the semiconductor laser module 10 as a part of a pumping light source can be improved. However, it is difficult to output laser light mainly in the wavelength band B using only normal laser oscillation of the semiconductor laser element 12.

[0034] Therefore, in the semiconductor laser module 10, a reflecting mirror 511 such as a VBG element (VBG: volume bragg grating) that selectively reflects components of a specific wavelength band, i.e., components of the wavelength band B, is provided, and an external resonator is formed between the semiconductor laser element 12 and the reflecting mirror 511. This makes it possible to form a semiconductor laser module 10 that mainly outputs laser light of wavelength band B, which is different from the oscillation wavelength of the semiconductor laser element 12.

[0035] However, in this configuration, it has been found that the beam divergence angle, particularly in the slow axis direction, of the laser light output from the external resonator structure and coupled to the optical fiber 68 via the condenser lenses 64 and 65 increases as the driving power of the semiconductor laser element 12 increases. In this case, it is conceivable to provide an aperture that physically limits the divergence angle in the slow axis direction, but if the divergence angle in the slow axis direction of the laser light output from the external resonator structure is limited, the output of the laser light from the semiconductor laser module 10 will decrease by the amount of the limitation.

[0036] Therefore, as a result of extensive research, the inventors have found that by inserting aperture 111, which removes higher-order mode components contained in multimode laser light, into the external resonator and configuring the aperture 111 to remove the higher-order mode components of the multimode laser light, it is possible to limit the divergence angle of the laser light in the slow axis direction while suppressing the output reduction caused by aperture 111.

[0037] 1 and 2, in this embodiment, the aperture 111 is inserted in the external resonator, i.e., between the reflecting mirror 511 and the plurality of semiconductor laser elements 12. In this case, a plurality of laser beams arranged at intervals in the Z direction pass through the aperture 111. That is, the aperture 111 restricts the width of the laser beam in the slow axis direction for each of the laser beams arranged at intervals in the Z direction so as to remove higher-order components of the multimode laser beam.

[0038] Through experimental research, the inventors compared the laser light output for the same magnitude of supply current (2 to 15 [A]) supplied to semiconductor laser module 10 among the following three configurations (1) to (3): (1) Reference Example 1: a configuration that does not include aperture 111 at all; (2) Reference Example 2: a configuration in which aperture 111 is provided outside the external resonator, i.e., between reflecting mirror 511 and condenser lens 64, instead of inside the external resonator; and (3) this embodiment: a configuration in which aperture 111 is provided inside the external resonator. The results showed that the reduction rate of the laser light output in the configuration of Reference Example 2 relative to the laser light output in the configuration of Reference Example 1 was 2 to 18 [%]. In contrast, the reduction rate of the laser light output in the configuration of this embodiment relative to the laser light output in the configuration of Reference Example 1 was 0 to 6 [%]. In this way, it was confirmed that by providing the aperture 111 inside the external resonator as in this embodiment, rather than outside the external resonator as in Reference Example 2, it is possible to significantly suppress the decrease in output compared to a configuration that does not have any aperture 111 at all (Reference Example 1).

[0039] FIG. 4 is a perspective view showing a specific configuration example of the aperture 111A (111). The aperture 111A has a rectangular, plate-like shape extending in the Z direction, with a substantially constant thickness and width in the X direction. The aperture 111A has two shielding portions 111a extending parallel to each other at equal intervals in the Z direction, and a U-shaped, notched opening O that opens in the Z direction is provided between the two shielding portions 111a. In the aperture 111A, multiple laser beams arranged at intervals in the Z direction pass through the opening O. Within the range through which the multiple laser beams pass at intervals in the Z direction, the position and width Ws of the opening O in the X direction (the interval between the shielding portions 111a) are constant regardless of the position in the Z direction. The width Ws of the opening O in the slow-axis direction of the aperture 111A, i.e., in the X direction, is set to a size that can remove high-order components of multimode laser beams. 5 is an enlarged plan view of a portion of the semiconductor laser module 10. As shown in Fig. 5, when the emission width in the slow-axis direction of the semiconductor laser element 12 is h, the maximum divergence angle is θ, and the focal length of the collimator lens 60 in the slow-axis direction is f, the width Ws is set to satisfy, for example, Ws < h + 2f tan(θ / 2). In this configuration, the shielding portion 111a removes higher-order components of the multimode laser beam by partially blocking the laser beam in the X direction and at the end of the passage region intersecting with the Y direction of the laser beam and in the direction opposite to the X direction.

[0040] Furthermore, in the external resonator structure, the aperture 111A can remove higher-order components of multimode laser light from both the laser light traveling from the semiconductor laser element 12 to the reflecting mirror 511 and the laser light traveling from the reflecting mirror 511 to the semiconductor laser element 12. This makes it possible to more reliably remove higher-order components of multimode laser light.

[0041] Furthermore, through extensive research by the inventors into the configuration in which the aperture 111 is provided inside the external resonator as in this embodiment, it has been found that the lower the front surface reflectivity of the semiconductor laser element 12, the more the output efficiency of the laser light relative to the supplied current can be increased.

[0042] First, the effective reflectance R when the reflecting mirror 511 and the front surface of the semiconductor laser element 12 are replaced with one mirror is ｅｆｆ is expressed as the following equation (1). Here, R ｆ : front surface reflectance of the semiconductor laser element 12, C: coupling efficiency of light emitted from the front surface (emission end surface) of the semiconductor laser element 12 to the reflection mirror 511, R ＶＢＧ : the reflectance of the reflecting mirror 511. From equation (1), the gain g of the semiconductor laser element 12 can be expressed as the following equation (2). Here, α ｉ : transparentization carrier density, L: cavity length of the semiconductor laser element 12, R ＨＲ : the rear surface reflectance of the semiconductor laser element 12. From equation (2), the threshold carrier density N ｔｈ can be expressed as the following equation (3). Here, N ｔｒ : transparent carrier density, Γ: active layer confinement coefficient, G ０ : is the gain coefficient. The threshold carrier density N in Equation (3) ｔｈ is the amount of current required for laser oscillation, and the larger this value, the more difficult it is to oscillate the laser, that is, the lower the output of the laser light relative to the supplied current (output efficiency).

[0043] FIG. 6 shows the relationship between the coupling efficiency C and the threshold carrier density N ｔｈ The relationship between the front surface reflectance R ｆ 6 shows two examples of the front surface reflectance R ｆ The lower the threshold carrier density N ｔｈ , that is, it becomes more difficult for the semiconductor laser element 12 to oscillate.

[0044] Furthermore, the coupling efficiency C of the higher-order mode component is estimated to be about 0 to 0.2, but when attempting to oscillate in a state in which the higher-order mode component is included in the external resonator, that is, when a component where C=0 to 0.2 is included, it can be seen from Fig. 6 that a higher power is required. In contrast, according to this embodiment, oscillation can be performed while removing the higher-order mode component in the resonator (external resonator) by the aperture 111, so that the current supply can be reduced by that amount, and it is estimated that this can increase the output efficiency. Furthermore, the threshold carrier density N ｔｈ is the front surface reflectance R ｆ The effect of removing the higher-order mode components described above is due to the front surface reflectance R ｆ It is estimated that this phenomenon appears more significantly in the semiconductor laser device 12 where the temperature is low.

[0045] Next, let us consider the optical output when the reflecting mirror 511 and the front surface of the semiconductor laser element 12 are replaced with one mirror. ｆ , the optical output from the rear surface of the system is P ｂ and the forward light just before the light output end face of the semiconductor laser element 12 is P' ｆ , and the backward light in front of the rear surface of the semiconductor laser element 12 is P' ｂ Then, P' ｂ and P' ｆ The relationship can be expressed as the following equation (4). In addition, the ratio F of the energy coupled to the outside of the semiconductor laser element 12 that can be extracted from the front surface by passing through the reflecting mirror 511 is ｆ can be expressed as the following equation (5). Here, T ｅｆｆ : effective transmittance at the front surface of the system. The slope efficiency SE of the semiconductor laser element 12 can be expressed by the following equation (6). Here, η ｉ : Internal quantum efficiency, α ｍ 7 shows the relationship between the slope efficiency SE and the front surface reflectivity R of the semiconductor laser element 12. ｆ 5 is a graph showing the relationship between the coupling efficiency C and the reflectance R of the reflecting mirror 511 based on the formula (6).ＶＢＧ = 10[%]. As the reflectance of the reflecting mirror 511 increases, the mirror loss increases and the optical output decreases, so a value of about 10[%] is generally adopted. From FIG. 7, the front surface reflectance R ｆ It can be seen that the smaller the slope efficiency SE, the higher the slope efficiency SE. Furthermore, it can be seen that the slope efficiency SE tends to increase when the front surface reflectance of the semiconductor laser element 12 is 2% or less. Through extensive research by the inventors using experiments and simulations, it has been found that, from the above-mentioned perspective, the front surface reflectance of the semiconductor laser element 12 is preferably 2% or less, and more preferably 0.5% or less. Furthermore, the front surface reflectance is set to 0.01% or more. Furthermore, it has been found that the reflectance of the reflecting mirror 511 constituting such an external resonator is preferably 4% or more. This is to ensure wavelength selectivity.

[0046] As described above, the semiconductor laser module 10 of this embodiment is capable of outputting laser light in a desired wavelength band, while limiting the divergence angle in the slow axis direction and increasing output efficiency, i.e., reducing unnecessary energy consumption.

[0047] In this embodiment, the aperture 111 and the reflecting mirror 511 are spaced apart from each other. This configuration has the advantage that, for example, the installation position and attitude (angle) of the aperture 111 can be adjusted separately from the reflecting mirror 511.

[0048] 8 is a perspective view showing an aperture 111B (111) included in the semiconductor laser module 10 of the second embodiment. The aperture 111B can be provided in place of the aperture 111A of the semiconductor laser module 10 of the first embodiment, and the same effect as that obtained by providing the aperture 111 can be obtained in this configuration as well.

[0049] However, in the aperture 111B of this embodiment, the two shielding portions 111a are configured as separate bodies, which has the advantage that the output characteristics of the semiconductor laser module 10 can be adjusted by finely adjusting the width Ws of the gap G between the two shielding portions 111a.

[0050] 9 is a plan view of a part of the semiconductor laser module 10 of the third embodiment. The configuration shown in FIG. 9 can be provided in place of the semiconductor laser module 10 of the first embodiment, and the effect of providing the aperture 111 can also be obtained in this configuration.

[0051] However, in this embodiment, the aperture 111 is integrated with the reflecting mirror 511. In this case, the effort and cost required to manufacture the semiconductor laser module 10 may be reduced compared to when the aperture 111 and the reflecting mirror 511 are separately attached to the base 24. In this case, only the aperture 111 of the subassembly of the aperture 111 and the reflecting mirror 511 may be fixed to the base 24, or only the reflecting mirror 511 of the subassembly may be fixed to the base 24. The aperture 111 or the reflecting mirror 511 is fixed onto the base 24 via a bonding material such as an ultraviolet-curable adhesive.

[0052] [Fourth Embodiment] Figure 10 is an exemplary schematic diagram showing multiple semiconductor laser elements 12, a reflecting mirror 511, and two condenser lenses 64 and 65 of a semiconductor laser module 10 according to a fourth embodiment, viewed in the slow-axis direction. As in the first embodiment, in this embodiment, an external resonator is configured between one reflecting mirror 511 and multiple semiconductor laser elements 12 positioned at different positions in the Z direction. In this configuration, as shown in Figure 10, the reflecting mirror 511 preferably has a constant thickness in the Y direction and is disposed perpendicular to the Y direction. Preferably, multiple laser beams dispersed in the Z direction travel parallel to each other in the Y direction, are incident on the reflecting mirror 511 at approximately right angles, and are reflected in the opposite direction of the Y direction. Here, we consider a state in which the coupling efficiency of the multiple laser beams to the optical fiber 68 is maximized when the laser beams incident on the condenser lens 64 travel parallel to each other in the Y direction.

[0053] 11 is a schematic diagram of a reference example including a condenser lens 64R configured as a spherical lens (cylindrical lens) viewed in the slow axis direction. As shown in FIG. 11, when the condenser lens 64R is configured as a spherical lens, a desired coupling efficiency can be obtained for laser beams radially incident on the reflecting mirror 511 due to aberrations of the condenser lens 64R. In other words, it is difficult to obtain the desired coupling efficiency for multiple laser beams incident on the reflecting mirror 511 at approximately right angles.

[0054] Therefore, in this embodiment, the condenser lens 64 is made an aspherical (non-cylindrical) cylindrical lens to realize the state shown in Fig. 10. This allows an external resonator to be formed between one reflecting mirror 511 and multiple semiconductor laser elements 12 positioned at different positions in the Z direction, and multiple laser beams from each external resonator can be focused onto a convergence point at the end of one optical fiber 68 and coupled with a desired coupling efficiency. The condenser lens 64 is an example of a first lens.

[0055] 12 is an exemplary schematic diagram of an optical fiber laser 94 according to a fifth embodiment. The optical fiber laser 94 includes a light source device 80, a pump combiner 96, a rare-earth doped optical fiber 98, an output optical fiber 100, a high-reflection FBG 102 (fiber bragg grating (FBG)), and a low-reflection FBG 104.

[0056] The light source device 80 functions as a pumping light source for an optical fiber laser 94 and includes a plurality of semiconductor laser modules 10 according to the above embodiment arranged in parallel. The output ends of optical fibers 68 transmitting laser light output from each semiconductor laser module 10 are respectively coupled to a plurality of input ports of a multi-input, single-output pump combiner 96. The output ports of the pump combiner 96 are connected to input ends of rare-earth-doped optical fibers 98. The output ends of the rare-earth-doped optical fibers 98 are connected to input ends of output optical fibers 100. Note that, instead of the pump combiner 96, other configurations may be used as the input section for inputting the laser light output from the plurality of semiconductor laser modules 10 into the rare-earth-doped optical fibers 98. For example, the optical fibers 68 corresponding to the semiconductor laser modules 10 may be arranged side by side, and the laser light output from the plurality of optical fibers 68 may be input into the input end of the rare-earth-doped optical fiber 98 using an input section such as an optical system including a lens. In this manner, the optical fiber laser 94 serving as a pumping light source for the light source device 80 according to this embodiment is configured.

[0057] In the optical fiber laser 94, the laser light output from each of the semiconductor laser modules 10 passes through the optical fiber 68, is combined by the pump combiner 96, and is output from its output port. The pump combiner 96 serving as an input unit inputs the laser light as pumping light output from its output port to the input end of the rare-earth doped optical fiber 98. In the optical fiber laser 94, a resonator is formed by the rare-earth doped optical fiber 98, the high-reflection FBG 102, and the low-reflection FBG 104. The optical fiber 68 and the pump combiner 96 are examples of optical components.

[0058] In the rare-earth-doped optical fiber 98, the propagating pump light is absorbed by the rare-earth element doped in the core, causing a population inversion between the ground state and the metastable state, resulting in the emission of light. The emitted light undergoes laser oscillation due to the optical amplification effect of the rare-earth-doped optical fiber 98 and the action of the resonator formed by the high-reflection FBG 102 and the low-reflection FBG 104. In this way, laser light is generated by laser oscillation in the optical fiber laser 94. The generated laser light is output from the output end of the output optical fiber 100 connected to the output end of the rare-earth-doped optical fiber 98. The rare-earth-doped optical fiber 98 is, for example, an Yb-doped double-clad fiber, which is an example of an amplifying fiber.

[0059] While the above describes exemplary embodiments of the present invention, the above embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the specifications of each configuration, shape, and the like (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be appropriately modified and implemented.

[0060] The present invention can be used in semiconductor laser modules, light source devices, and optical fiber lasers.

[0061] DESCRIPTION OF SYMBOLS 10...Semiconductor laser module 12...Semiconductor laser element 14...Optical system 18...Output section 20...Terminal section 24...Base 38...Step section 40...Step surface 42...Submount 58...Collimating lens (first optical component) 60...Collimating lens (first optical component) 62...Mirror (first optical component) 64...Condenser lens (first lens) 64R...Condenser lens 65...Condenser lens 68...Optical fiber (output optical fiber, optical component) 80...Light source device 94...Optical fiber laser 96...Pump combiner (optical component) 98...Rare earth doped optical fiber (amplification optical fiber) 100...Output optical fiber 102...High reflection FBG 104...Low reflection FBG 111, 111A, 111B...Aperture 111a...Shielding section 511...Reflecting mirror B...Wavelength band G...Gap O...Opening Ws...width X...direction Y...direction Z...direction λc...center wavelength

Claims

1. A semiconductor laser module comprising: a plurality of semiconductor laser elements each outputting multimode laser light as laser light and having substantially the same fast axis direction and slow axis direction; a first optical component arranging the laser light output from the plurality of semiconductor laser elements at intervals in the fast axis direction; a reflecting mirror that reflects components of a specific wavelength band from the light output from the semiconductor laser elements and arranged at intervals in the fast axis direction, and that forms an external resonator between the plurality of semiconductor laser elements; an aperture provided within the external resonator that limits the width of the laser light in the slow axis direction so as to remove higher-order mode components of the multimode laser light from the laser light arranged at intervals in the fast axis direction; and a focusing lens that couples the laser light output from the external resonator to an output optical fiber.

2. The semiconductor laser module according to claim 1, wherein the aperture is located between the reflecting mirror and the first optical component.

3. A semiconductor laser module according to claim 1 or 2, wherein the front surface reflectance of said semiconductor laser element is 2% or less.

4. The semiconductor laser module according to claim 3, wherein the front surface reflectance of the semiconductor laser element is 0.5% or less.

5. A semiconductor laser module according to claim 1 or 2, wherein the reflectance of said reflecting mirror is 4% or more.

6. The semiconductor laser module according to claim 1 or 2, wherein the aperture and the reflecting mirror are spaced apart.

7. The semiconductor laser module according to claim 1 or 2, wherein the aperture and the reflecting mirror are integrated.

8. The semiconductor laser module described in claim 1, wherein the focusing lens includes a first lens as an aspherical lens that focuses the plurality of parallel laser beams dispersed in the fast axis direction onto a convergence point at the end of the output optical fiber, and the reflecting mirror reflects the plurality of parallel laser beams onto the plurality of semiconductor laser elements.

9. A light source device comprising the semiconductor laser module according to claim 1 or 2.

10. An optical fiber laser comprising: a light source device according to claim 9; an amplification optical fiber; and an optical component for guiding laser light output from said light source device to said amplification optical fiber.

11. The optical fiber laser according to claim 10, wherein the reflecting mirror reflects components of a wavelength band substantially centered around a wavelength at which the absorption spectrum of the Yb-doped double-clad fiber is high.

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