WO2025205369A1 - Semiconductor laser module, light source device, and optical fiber laser - Google Patents

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

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

Conventionally, semiconductor laser modules have been known in which laser light output from multiple light-emitting elements is directed to the end of an optical fiber via multiple optical components (see, for example, Patent Document 1).

International Publication No. 2019/160038

It would be beneficial if this type of semiconductor laser module could output laser light in the desired wavelength band while consuming minimal energy.

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

The 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 that arranges 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 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.

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

In the semiconductor laser module, the front surface reflectivity of the semiconductor laser element may be 2% or less.

In the semiconductor laser module, the front surface reflectivity of the semiconductor laser element may be 0.5% or less.

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

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

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

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

The light source device of the present invention includes, for example, the semiconductor laser module.

The optical fiber laser of the present invention comprises, 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.

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

The present invention makes it possible to obtain a semiconductor laser module, a light source device, and an optical fiber laser with a more improved and novel configuration.

FIG. 1 is an exemplary schematic plan view of a semiconductor laser module according to the first embodiment. FIG. 2 is an exemplary schematic perspective view of the semiconductor laser module of 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 schematic perspective view of an aperture included in the semiconductor laser module of the first embodiment. FIG. 5 is an exemplary schematic plan view showing an enlarged portion of the semiconductor laser module of the first embodiment. FIG. 6 is a graph illustrating the relationship between the coupling efficiency of light emitted from the semiconductor laser element of the semiconductor laser module of the first embodiment to the 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 the slope efficiency and the front surface reflectance of the semiconductor laser element in the semiconductor laser module of the first embodiment. FIG. 8 is an exemplary schematic perspective view of an aperture included in the semiconductor laser module of the second embodiment. FIG. 9 is an exemplary schematic plan view of a part of the semiconductor laser module according to the third embodiment. FIG. 10 is an exemplary schematic diagram showing a plurality of laser elements, a reflecting mirror, and two condenser lenses of the semiconductor laser module according to the 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 the semiconductor laser module of the reference example as viewed in the slow axis direction. FIG. 12 is an exemplary schematic configuration diagram of an optical fiber laser according to the fifth embodiment.

Below, exemplary embodiments of the present invention are disclosed. The configurations of the embodiments shown below, as well as the actions and results (effects) brought about by said configurations, are merely examples. The present invention can also be realized with 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.

The multiple embodiments described below have similar configurations. Therefore, according to the configuration of each embodiment, similar actions and effects based on the similar configurations can be obtained. Furthermore, below, similar configurations will be assigned similar reference numerals, and duplicate explanations may be omitted.

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

In each figure, the X direction is represented by arrow X, the Y direction is represented by arrow Y, and the Z direction is represented by arrow Z. The X, Y, and Z directions intersect and are perpendicular to each other. The direction behind arrow X is referred to as the opposite direction of the X direction, the direction behind arrow Y is referred to as the opposite direction of the Y direction, and the direction behind arrow Z is referred to as the opposite direction of the Z direction. Furthermore, each figure is schematic, and the shape, dimensions, proportions, etc. of each part may differ from the actual ones.

[First embodiment]
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.

The semiconductor laser module 10 comprises 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.

The output section 18 supports an optical fiber 68 that transmits the output light. The terminal section 20 is a connection terminal to which a wiring conductor 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.

As shown in Figures 1 and 2, the base 24 supports each component included in the semiconductor laser module 10. The base 24 can also be referred to as a support member or a mounted member.

As shown in FIG. 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 generally flat, all facing the Z direction, and intersect with and are perpendicular to the Z direction.

Semiconductor laser elements 12 with the same specifications are mounted on each step surface 40. Each of the multiple semiconductor laser elements 12 outputs 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 their slow axis directions are substantially the same. In this embodiment, each of the semiconductor laser elements 12 outputs multimode laser light as laser light. In this embodiment, the semiconductor laser element 12 is mounted on a submount 42 to form a chip-on-submount, but this is not limited to this and may be housed in a case and unitized, for example.

Furthermore, collimating lenses 58, 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, then collimated in the slow axis direction by the collimating lens 60, and travels to the mirror 62.

The mirrors 62 each reflect the laser light traveling in the X direction and redirect 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 of the Y direction to the X direction and the opposite direction of the X direction.

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, reflecting mirror 511, and focusing lenses 64 and 65. The focusing lens 64 focuses the laser light in the fast axis direction (Z direction and the direction opposite to the Z direction), and the focusing lens 65 focuses the laser light in the slow axis direction (X direction and the direction opposite to the X direction). The reflecting mirror 511 and aperture 111 will be described in more detail later.

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 surface 40), the multiple semiconductor laser elements 12, the collimating lenses 58, 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, 60 and the mirror 62 interposed between the semiconductor laser element 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. The configurations of the step portion 38, step surface 40, and optical system 14 are not limited to those illustrated in Figures 1 and 2, and may be any configuration that allows multiple laser beams input to the reflecting mirror 511 to be aligned at intervals in the Z direction. Furthermore, the semiconductor laser module 10 may include multiple parallel configurations including the step portion 38, step surface 40, and 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. Note that "multiple laser beams aligned at intervals" means that the optical axes of the multiple laser beams are aligned at intervals.

Figure 3 is a graph showing an example of the absorption rate as a function of wavelength of a Yb-doped double-clad fiber included in an optical fiber laser. When the semiconductor laser module 10 outputs laser light that mainly contains components in wavelength band B: λc ± 3 nm with a center wavelength λc of 976 nm in Figure 3, for example, the semiconductor laser module 10 can be used as part of the excitation light source to increase the output efficiency of an optical fiber laser that includes a Yb-doped double-clad fiber as an amplification fiber. However, it is difficult to output laser light mainly in wavelength band B using only normal laser oscillation of the semiconductor laser element 12.

The semiconductor laser module 10 is therefore provided with a reflective 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 above-mentioned wavelength band B, and an external resonator is formed between the semiconductor laser element 12 and the reflective mirror 511. This makes it possible to configure 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.

However, with 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 possible 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 that amount.

As a result of extensive research, the inventors discovered that by inserting an aperture 111 that 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 the aperture 111.

In other words, in this embodiment, as shown in Figures 1 and 2, the aperture 111 is inserted inside the external resonator, i.e., between the reflecting mirror 511 and the multiple semiconductor laser elements 12. In this case, multiple laser beams spaced apart in the Z direction pass through the aperture 111. That is, the aperture 111 limits the width of the slow axis direction of each of the laser beams spaced apart in the Z direction so as to remove higher-order components of the multimode laser beam.

Through experimental research, the inventors have found that the laser light output for the same magnitude of supply current (2 to 15 A) supplied to the semiconductor laser module 10 can be improved by using the following three configurations (1) to (3):
(1) Reference Example 1: A configuration in which no aperture 111 is provided,
(2) Reference Example 2: A configuration in which the aperture 111 is provided outside the external resonator, i.e., between the reflecting mirror 511 and the condenser lens 64, instead of being provided inside the external resonator.
(3) This embodiment: A configuration in which the aperture 111 is provided inside the external resonator.
We compared the following.
As a result, 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 reduction in output compared to the configuration (Reference Example 1) that does not include the aperture 111 at all.

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 in the slow axis direction of the collimator lens 60 is f, the width Ws can be expressed as, 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 at the end portions in the X direction and the opposite direction to the X direction of the passage region that intersects with the Y direction of the laser beam.

Furthermore, in the external resonator structure, 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.

Furthermore, through extensive research by the inventors into a configuration in which the aperture 111 is provided inside the external resonator, as in this embodiment, it was discovered that the lower the front surface reflectivity of the semiconductor laser element 12, the higher the laser light output efficiency relative to the supplied current. This will be considered below.

First, when the reflecting mirror 511 and the front surface of the semiconductor laser element 12 are replaced with one mirror, the effective reflectance R _eff is given by the following equation (1).
where R _f is the front surface reflectance of the semiconductor laser element 12 , C is the coupling efficiency of the light emitted from the front surface (emitting end face) of the semiconductor laser element 12 to the reflecting mirror 511 , and R _VBG is 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).
where α _i is the transparentizing carrier density, L is the cavity length of the semiconductor laser element 12, and R _HR is the rear surface reflectance of the semiconductor laser element 12.
From equation (2), the threshold carrier density N _th in the external resonator can be expressed as the following equation (3).
Here, N _tr is the transparent carrier density, Γ is the active layer confinement coefficient, and G ₀ is the gain coefficient.
The threshold carrier density N _th in equation (3) is the amount of current required for laser oscillation, and the larger this value is, the more difficult it is to oscillate the laser, i.e., the lower the laser light output (output efficiency) relative to the supplied current is.

6 is a graph showing the relationship between the coupling efficiency C and the threshold carrier density _Nth for two examples of the front surface reflectivity _Rf . As can be seen from FIG. 6, the lower the front surface reflectivity _Rf , the higher the threshold carrier density _Nth , i.e., the more difficult it is for the semiconductor laser device 12 to oscillate.

Furthermore, the coupling efficiency C of the higher-order mode component is estimated to be approximately 0 to 0.2. However, if oscillation is attempted in a state in which the higher-order mode component is included in the external resonator, i.e., when the component where C = 0 to 0.2 is included, as shown in Figure 6, a higher power is required. In contrast, according to this embodiment, oscillation can be achieved while removing the higher-order mode component in the resonator (external resonator) using the aperture 111, so the current supply can be reduced accordingly, and it is estimated that this can increase the output efficiency. Furthermore, the threshold carrier density _Nth for the component where C = 0 to 0.2 tends to increase as the front surface reflectivity _Rf decreases, and it is estimated that the effect of removing the above-mentioned higher-order mode component is more pronounced in semiconductor laser elements 12 with low front surface reflectivity _Rf .

Next, consider the optical output when the reflecting mirror 511 and the front surface of the semiconductor laser element 12 are replaced with a single mirror. If the optical output from the front surface of the system is _Pf , the optical output from the rear surface of the system is _Pb , the forward light just before the emission end surface of the semiconductor laser element 12 is _P'f , and the backward light just before the rear surface of the semiconductor laser element 12 is _P'b , the relationship between _P'b and _P'f can be expressed by the following equation (4):
Furthermore, the ratio _Ff of the energy coupled out of the semiconductor laser element 12 that passes through the reflecting mirror 511 and is extracted from the front surface can be expressed by the following equation (5).
where T _eff is the effective transmittance of the front surface of the system.
The slope efficiency SE of the semiconductor laser device 12 can be expressed by the following equation (6).
Here, η _i is the internal quantum efficiency, and α _m is the mirror loss in the system.
FIG. 7 is a graph showing the relationship between the slope efficiency SE and the front surface reflectivity _Rf of the semiconductor laser element 12 based on equation (6). Here, the coupling efficiency C is set to 1, and the reflectivity R _VBG of the reflecting mirror 511 is set to 10%. Since the higher the reflectivity of the reflecting mirror 511, the greater the mirror loss and the lower the optical output, so a value of about 10% is generally used. It can be seen from FIG. 7 that the smaller the front surface reflectivity _Rf , the higher the slope efficiency SE. Furthermore, it can be seen that the slope efficiency SE tends to increase when the front surface reflectivity of the semiconductor laser element 12 is 2% or less.
Through extensive research by the inventors through 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.

As explained 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.

Furthermore, 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.

Second Embodiment
8 is a perspective view showing the 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 effect of providing the aperture 111 can be obtained even in this configuration.

However, in the aperture 111B of this embodiment, the two shielding portions 111a are configured as separate bodies. In this case, the advantage is that the output characteristics of the semiconductor laser module 10 can be adjusted by fine-tuning the width Ws of the gap G between the two shielding portions 111a.

[Third embodiment]
9 is a plan view of a portion 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 with this configuration.

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 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 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 reflecting mirror 511 is fixed to the base 24 via a bonding material such as an ultraviolet-curing adhesive.

[Fourth embodiment]
10 is an exemplary schematic diagram showing the plurality of semiconductor laser elements 12, a reflecting mirror 511, and two condenser lenses 64 and 65 of the semiconductor laser module 10 of the fourth embodiment as viewed in the slow-axis direction. In this embodiment, as in the first embodiment, an external resonator is configured between one reflecting mirror 511 and the plurality of semiconductor laser elements 12 positioned at different positions in the Z direction. In this configuration, as shown in FIG. 10 , the reflecting mirror 511 is preferably disposed so as to have a constant thickness in the Y direction and be perpendicular to the Y direction. Preferably, the plurality of 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 to the Y direction. Here, we consider a state in which the coupling efficiency of the plurality of 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.

Figure 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 Figure 11, when the condenser lens 64R is configured as a spherical lens, the aberration of the condenser lens 64R makes it possible to obtain the desired coupling efficiency for laser light that is radially incident on the reflecting mirror 511. In other words, it becomes difficult to obtain the desired coupling efficiency for multiple laser light beams that are incident on the reflecting mirror 511 at approximately right angles.

In this embodiment, the state shown in Figure 10 is achieved by using an aspherical (non-cylindrical) cylindrical lens as the focusing lens 64. 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 combined with the desired coupling efficiency. The focusing lens 64 is an example of a first lens.

Fifth Embodiment
12 is an exemplary schematic diagram of an optical fiber laser 94 according to the 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.

The light source device 80 functions as an excitation light source for the optical fiber laser 94 and has multiple semiconductor laser modules 10 of the above embodiment arranged in parallel. The output ends of the optical fibers 68 that transmit the laser light output from each semiconductor laser module 10 are respectively coupled to multiple input ports of a multiple-input, single-output pump combiner 96. The output port of the pump combiner 96 is connected to the input end of a rare-earth-doped optical fiber 98. The output end of the rare-earth-doped optical fiber 98 is connected to the input end of an output optical fiber 100. Note that instead of the pump combiner 96, other configurations can be used as the input section that inputs the laser light output from the multiple semiconductor laser modules 10 into the rare-earth-doped optical fiber 98. For example, optical fibers 68 corresponding to the semiconductor laser modules 10 can be arranged side by side, and the laser light output from the multiple optical fibers 68 can be input to 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 that serves as an excitation light source for the light source device 80 of this embodiment is configured.

In the optical fiber laser 94, the laser light output from each of the semiconductor laser modules 10 is combined by the pump combiner 96 via the optical fiber 68 and output from its output port. The pump combiner 96, which serves as an input section, inputs the laser light output from its output port as excitation light 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 pump combiner 96 are examples of optical components.

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 metastable state, resulting in the emission of light. The emitted light undergoes laser oscillation due to the optical amplification action 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 oscillation generates laser light 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, and is an example of an amplification fiber.

The above describes exemplary embodiments of the present invention, but the above embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in a variety of 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 modified as appropriate.

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

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 (optical fiber for amplification)
100... output optical fiber 102... high-reflection FBG
104...Low reflection FBG
111, 111A, 111B... aperture 111a... shielding portion 511... reflecting mirror B... wavelength band G... gap O... opening Ws... width X... direction Y... direction Z... direction λc... center wavelength

Claims (11)

a plurality of semiconductor laser elements each outputting multimode laser light as laser light and having fast axis directions and slow axis directions that are substantially the same;
a first optical component that arranges the laser beams 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 among the light beams output from the semiconductor laser elements and arranged at intervals in the fast axis direction, and that forms an external resonator between itself and the plurality of semiconductor laser elements;
an aperture provided in the external resonator and configured to limit a width of the laser beam in the slow axis direction so as to remove higher-order mode components of multimode laser beams from the laser beams arranged at intervals in the fast axis direction;
a focusing lens that couples the laser light output from the external resonator into an output optical fiber;
A semiconductor laser module comprising: The semiconductor laser module described in claim 1, wherein the aperture is located between the reflecting mirror and the first optical component. The semiconductor laser module of claim 1 or 2, wherein the front surface reflectivity of the semiconductor laser element is 2% or less. The semiconductor laser module of claim 3, wherein the front surface reflectivity of the semiconductor laser element is 0.5% or less. The semiconductor laser module of claim 1 or 2, wherein the reflectance of the reflecting mirror is 4% or more. The semiconductor laser module of claim 1 or 2, wherein the aperture and the reflecting mirror are spaced apart. The semiconductor laser module described in claim 1 or 2, wherein the aperture and the reflecting mirror are integrated. the condensing lens includes a first lens as an aspherical lens that condenses the plurality of parallel laser beams dispersed in the fast axis direction to a convergence point at an end of the output optical fiber,
2. The semiconductor laser module according to claim 1, wherein the reflecting mirror reflects the plurality of parallel laser beams toward the plurality of semiconductor laser elements. A light source device equipped with the semiconductor laser module described in claim 1 or 2. The light source device according to claim 9 ;
an amplifying optical fiber;
an optical component that guides the laser light output from the light source device to the amplification optical fiber;
An optical fiber laser comprising: The optical fiber laser described in claim 10, wherein the reflecting mirror reflects components of a wavelength band roughly centered around a wavelength at which the absorption spectrum of the Yb-doped double-clad fiber is high.