JP2020120000A - Light source unit - Google Patents

Abstract

To provide a novel light source unit suitable for spatial beam coupling.SOLUTION: A light source unit 100 includes: a package 10 including a LD (laser diode) 12 having an emitter region E for emitting laser light on an end face 12F and a window member 14; a first lens system 20, for receiving the laser light that has passed through the window member 14 and forming an image (virtual light source) E' of the emitter region on an image plane 22; and a second lens system 30 for converting the laser light that has passed through the image plane into a collimated beam B or a convergent beam for emission.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to a light source unit.

BACKGROUND ART Various types of materials are subjected to processing such as cutting, drilling, and marking, and welding of metal materials using a high-power and high-intensity laser beam. Conventionally, a part of the carbon dioxide gas laser device and the YAG solid-state laser device used for such laser processing is being replaced by a fiber laser device having high energy conversion efficiency. A semiconductor laser diode (hereinafter, simply referred to as LD) is used as an excitation light source of the fiber laser device. In recent years, along with the increase in output of LDs, a technique of using the LDs as a light source of a laser beam for directly irradiating and processing a material is being developed, not as an excitation light source. Such a technique is called a direct diode laser (DDL) technique.

Patent Document 1 discloses an example of a laser light source that increases a light output by combining a plurality of laser beams emitted from a plurality of LDs. The combination of multiple laser beams is referred to as "spatial beam combination" and can be used to increase the light output of, for example, the excitation light source of fiber laser devices and DDL devices.

U.S. Pat. No. 7733932

There is a need for a more reliable laser light source suitable for spatial beam combination, and a laser processing apparatus including such a laser light source.

The light source unit of the present disclosure is, in a non-limiting and exemplary embodiment, a sealed semiconductor laser package, which is a laser diode having an emitter region for emitting a laser beam on an end face, and which transmits the laser beam. A semiconductor laser package including a window member; a first lens system that receives the laser light transmitted through the window member and forms an image of the emitter region on an image plane; and a laser beam that passes through the image plane. And a second lens system for converting into a collimated beam or a convergent beam and emitting the converted beam.

According to the embodiments of the present disclosure, a novel light source unit suitable for spatial beam combination can be provided.

FIG. 1A is a top view schematically showing a configuration example of a conventional light source unit 100P that collimates and outputs laser light emitted from an LD in a chip state. FIG. 1B is a side view of a configuration example of the light source unit 100P shown in FIG. 1A. FIG. 2 is a perspective view showing an example of the basic configuration of the LD 12. FIG. 3A is a schematic cross-sectional view parallel to the XZ plane showing a configuration example of a light source unit 100Q that collimates and outputs the laser light emitted from the LD 12 housed in the package 10. 3B is a schematic cross-sectional view parallel to the YZ plane of the light source unit 100Q shown in FIG. 3A. FIG. 4 is a diagram showing a basic configuration example of the light source unit 100 in the present embodiment. FIG. 5 is an enlarged view showing a main part of the light source unit 100. FIG. 6 is a diagram showing a form in which the first lens system 20 includes an objective lens system 24 and an imaging lens system 26. FIG. 7A is a schematic top view of the laser light source module 200 according to the present embodiment as seen from the direction normal to the XZ plane. FIG. 7B is a schematic side view of the laser light source module 200 according to the present embodiment as seen from the direction normal to the YZ plane. FIG. 7C is a schematic front view of the laser light source module 200 according to the present embodiment as seen from the direction normal to the XY plane. FIG. 8 is a perspective view schematically showing another configuration example including nine light source units 100. FIG. 9A is a diagram showing a configuration example of the optical system 160. FIG. 9B is a diagram showing another configuration example of the optical system 160. FIG. 10A is a diagram schematically showing a beam cross-sectional shape when five collimated beams B are incident on the fast axis converging lens FAF. FIG. 10B is a diagram schematically showing the beam cross-sectional shape when nine collimated beams B enter the fast axis converging lens FAF. FIG. 10C is a diagram schematically showing a beam cross-sectional shape when 9×2 rows of collimated beams B are incident on the fast axis converging lens FAF. FIG. 11 is a perspective view showing another configuration example of the laser light source module 200. FIG. 12 is a diagram showing another configuration example of the laser light source module 200. FIG. 13 is a diagram illustrating a configuration example of an embodiment of a direct diode laser (DDL) device according to the present disclosure. FIG. 14 is a diagram showing a configuration example of an embodiment of a fiber laser device according to the present disclosure.

Before describing the embodiments of the present disclosure, the knowledge found by the present inventors and the technical background thereof will be described.

FIG. 1A is a top view schematically showing a configuration example of a conventional light source unit 100P that collimates and outputs laser light emitted from an LD in a chip state, and FIG. 1B is a side view thereof. For reference, the accompanying drawings schematically show an XYZ coordinate system based on mutually orthogonal X-axis, Y-axis, and Z-axis.

The illustrated light source unit 100P includes an LD 12 that emits a laser beam L and an optical system 30P that collimates the laser beam L. In the illustrated example, the optical system 30P includes a fast axis collimator lens FAC and a slow axis collimator lens SAC which are sequentially arranged on the optical axis from a position close to the LD 12. Both the fast axis collimator lens FAC and the slow axis collimator lens SAC are cylindrical lenses (for example, cylindrical surface plano-convex lenses). The cylindrical lens has a curved surface that converges parallel light fluxes on a straight line (focal point). The curved surface has a shape corresponding to a part of the outer peripheral surface of the cylinder, and the curvature in the axial direction of the cylinder is zero. Spatial beam combining may be performed using a plurality of light source units 100P each having the illustrated configuration. The details of spatial beam combination will be described later.

FIG. 2 is a perspective view showing an example of the basic configuration of the LD 12. The configuration shown is simplified for purposes of illustration. In the example of FIG. 2, the LD 12 has a stripe-shaped p-side electrode 12P formed on the upper surface, an n-side electrode 12N formed on the lower surface, and an emitter region E located on the end face 12F. The laser light L is emitted from the emitter region E. The LD 12 has a semiconductor substrate and a plurality of semiconductor layers (semiconductor laminated structure) grown on the semiconductor substrate. The semiconductor laminated structure includes a light emitting layer that emits light by performing laser oscillation, and may have various known structures. The LD 12 in this example is a broad area type, and the emitter region E has a shape in which the size in the X-axis direction (for example, 50 μm or more) is significantly larger than the size in the Y-axis direction (for example, about 2 μm). The Y-axis size of the emitter region E is defined by the semiconductor laminated structure of the LD 12 (specifically, the thickness of the waveguide and the cladding layer, the refractive index ratio, etc.). The X-axis size of the emitter region E is defined by the X-axis size of a region in which a current flows in the direction crossing the light emitting layer, specifically, the width (gain waveguide width) of a ridge structure (not shown).

As shown in FIG. 2, the beam shape of the laser light L emitted from the emitter region E is asymmetric in the X-axis direction and the Y-axis direction. In FIG. 2, a far-field (far field) pattern of the laser light L is schematically shown. The laser light L has a beam shape that is approximated to a single-mode Gaussian beam in the Y-axis direction, but has a multi-mode beam shape with a small divergence angle as a whole in the X-axis direction. The divergence half-angle θ _{y0 in the} Y-axis direction is larger than the divergence half-angle θ _{x0 in the} X-axis direction. Since the laser light L in the Y-axis direction can be approximated to a Gaussian beam, if the beam radius at the beam waist position in the Y-axis direction is ω _o and the wavelength of the laser light L is λ, then θ _y0 =tan ⁻¹ (λ/πω) _o ) ≈ λ/(πω _o ) radians holds. In the case of a broad area laser diode in which λ is in the visible light range, θ _y0 is, for example, 20 degrees, and θ _x0 is, for example, 5 degrees. As a result, the Y-axis size of the laser light L diverges and expands relatively “fast” when propagating along the Z-axis direction. Therefore, the Y axis is called the "fast axis" and the X axis is called the "slow axis". Since the beam quality in the slow axis direction is multimode, it is relatively deteriorated as compared with the beam quality in the fast axis direction. As a result, the beam parameter product BPP (Beam Parameter Product) that defines the beam quality becomes relatively larger in the slow axis direction than in the fast axis direction. BPP is the product of the beam waist radius and the divergence half-angle in the far field.

In the illustrated example, the Z axis is parallel to the propagation direction (beam central axis) of the laser light L emitted from the LD 12. When explaining the operation of a single LD, it is convenient to make the origin of the XYZ coordinate system coincide with the center of the emitter region E. However, when describing spatial beam combination for a plurality of LDs, the origin of the XYZ coordinate system does not have to be determined in association with any of the LDs. Further, the directions of the plurality of LDs used for spatial beam combination need not be parallel to each other, and individual laser beams may be reflected by different mirrors to change the propagation direction. Therefore, the terms “fast axis direction” and “slow axis direction” in the present disclosure are not necessarily parallel to the “Y axis direction” and the “X axis direction” in the global XYZ coordinate system, respectively. , And depends on the asymmetry of the beam quality of each laser beam. That is, in the cross section orthogonal to the propagation direction of the laser beam, the direction having the lowest BPP is the “fast axis”, and the direction orthogonal to the fast axis is the “slow axis”.

Referring again to FIGS. 1A and 1B. In these figures, for simplification, the laser light L and the collimated beam B are simplified and represented by three representative rays. Of the three light rays, the central light ray is on the optical axis of the lens, and the other two light rays schematically show the positions that define the beam diameter. The beam diameter can be defined by the size of a region having a light intensity of 1/e ² or more with respect to the light intensity at the center of the beam. Here, e is the number of Napiers (about 2.71). The beam diameter or beam radius may be defined by other criteria.

As shown in FIG. 1B, the fast axis collimator lens FAC collimates the laser light L in a plane (YZ plane) including the propagation direction (Z axis) of the laser light L and the fast axis direction (Y axis). As shown in FIG. 1A, the slow axis collimator lens SAC collimates the laser light L in a plane (XZ plane) including the propagation direction (Z axis) and the slow axis direction (X axis). In order to perform these collimations, the fast axis collimator lens FAC and the slow axis collimator lens SAC are arranged so that the center of the emitter region E is located at the front focus of each.

In the near field, the cross section of the laser light L schematically shown in FIG. 2 reflects the shape of the emitter region E and has a shape shorter in the fast axis direction than in the slow axis direction. However, since the half-angle of divergence in the fast axis direction is large, the size in the fast axis direction rapidly increases as the distance from the emitter region E increases. Therefore, the shape and size of the cross section of the collimated beam B after passing through the optical system 30P depend on the positions of the fast axis collimator lens FAC and the slow axis collimator lens SAC on the optical path of the laser light L. More precisely, the fast axis size of the collimated beam B is defined by the divergence half-angle θ _y0 in the fast axis direction (or the numerical aperture of the fast axis collimator lens FAC) and the focal length of the fast axis collimator lens FAC. Similarly, the slow axis size of the collimated beam B is defined by the divergence half-angle θ _x0 (or the numerical aperture of the slow axis collimator lens SAC) in the slow axis direction and the focal length of the slow axis collimator lens SAC.

Generally, the closer the fast axis collimator lens FAC is to the end face 12F of the LD 12, more specifically, the emitter region E, the smaller the fast axis size of the collimated beam B can be made. In other words, the farther the fast axis collimator lens FAC is from the end surface 12F (emitter region E) of the LD 12, the larger the fast axis size of the collimated beam B becomes. Similarly, the farther the slow axis collimator lens SAC is from the end surface 12F (emitter region E) of the LD 12, the larger the slow axis size of the collimated beam B becomes. When changing the positions of the fast axis collimator lens FAC and the slow axis collimator lens SAC on the optical path of the laser light L, it is necessary to appropriately change the apertures and the focal lengths of the collimator lenses FAC and SAC. The center of the emitter region E is always arranged at the front focal points of the collimator lenses FAC and SAC.

When performing spatial beam combining using the plurality of light source units 100P having the above-described configuration, when the LD 12 having an oscillation wavelength shorter than the near infrared region is adopted and its light output is increased, the LD 12 is in operation due to the light collecting effect. There is a problem that dust and the like in the atmosphere may be attached to the emitter region E of 1 to reduce the light output. The substance that adheres to the emitter region is not limited to dust, and may be a deposit that is generated by chemically reacting the volatilized organic substance with the laser light L. As the wavelength of the laser light L becomes shorter and the light output becomes higher, the deterioration caused by the adhered matter becomes more remarkable. In order to avoid such a problem, when housing a plurality of LDs 12 in the housing, it is possible to assemble the housing while paying attention not to mix dust into the housing, and to seal the housing itself. .. However, since dust may adhere to parts such as the lens system and mirrors required for spatial beam combination, and it is difficult to increase the airtightness of the entire housing, maintaining high light output over a long period of time. I found it difficult to do.

As another problem solving means, it is conceivable to house each LD 12 in a sealed semiconductor laser package. The LD packaging technology is highly advanced, and has realized reliable operation for a long period of time. However, when the LD 12 is housed inside the semiconductor laser package, even if the fast axis collimator lens FAC is made to approach the emitter region of the LD 12, the semiconductor laser package physically interferes and cannot be brought sufficiently close to the focal point. Only the fast-axis collimator lens FAC having a relatively long distance can be adopted. Hereinafter, this point will be described.

FIG. 3A is a schematic cross-sectional view parallel to the XZ plane showing a configuration example of a light source unit 100Q that collimates and outputs the laser light emitted from the LD 12 housed in the semiconductor laser package 10, and FIG. It is a schematic cross section parallel to a surface. Hereinafter, the semiconductor laser package may be simply referred to as a package.

As can be seen from the figure, the window member 14 of the package 10 is located between the emitter region E of the LD 12 and the fast axis collimator lens FAC. You cannot get close to E. In the case of the light source unit 100P described above, the distance from the emitter region E of the LD 12 to the fast axis collimator lens FAC can be set to 0.3 millimeter (mm), for example. On the other hand, the distance from the emitter region E of the LD 12 housed inside the package 10 to the fast axis collimator lens FAC (meaning “optical distance” described later) increases to, for example, about 1.5 mm. Since the center of the emitter region E needs to be located at the front focal point of the fast axis collimator lens FAC, the focal length of the fast axis collimator lens FAC needs to be long, and the fast axis (Y axis) of the collimated beam B is inevitably obtained. The direction size increases several times. When the fast axis size of the collimated beam B is increased, there arises a disadvantage that the converging optical system used for performing the spatial beam combination becomes large. Details of this inconvenience will be described later.

According to the embodiment of the present disclosure, it becomes possible to solve such a problem. Hereinafter, a basic configuration example of the light source unit 100 according to the embodiment of the present disclosure will be described.

<Embodiment>
Light Source Unit FIG. 4 is a diagram showing a basic configuration example of the light source unit 100 in the present embodiment. FIG. 5 is a schematic diagram of a main part of the light source unit 100. In the illustrated example, the light source unit 100 includes a sealed package 10, a first lens system 20, and a second lens system 30.

The package 10 includes an LD 12 having an emitter region E for emitting the laser light L on an end face 12F and a window member 14 for transmitting the laser light L. The configuration of the package 10 is not particularly limited, and may be a TO-CAN type package of Φ5.6 mm or Φ9 mm, for example. The package 10 includes a stem having a lead terminal and a metal cap that covers the LD fixed to the stem, and a window member 14 having a light transmitting property is attached to the metal cap. A typical example of the window member 14 is a thin plate formed of optical glass (refractive index: 1.4 or more). The inside of the package 10 may be filled with an inert gas such as nitrogen gas or a rare gas having a high degree of cleanness and hermetically sealed. The LD 12 may be, for example, a semiconductor laser element that is formed of a nitride semiconductor material and outputs near-ultraviolet, blue-violet, blue, or green laser light. Specifically, the oscillation wavelength (center wavelength) of the LD 12 is in the range of 350 nm or more and 550 nm or less, for example. The LD 12 can be fixed to the stem via a submount having high thermal conductivity. The orientation of the LD 12 is not limited to the illustrated example, and the LD 12 may be arranged so as to reflect the laser light in the Z-axis direction by a mirror in the package.

The first lens system 20 receives the laser light L transmitted through the window member 14 and forms an image E′ of the emitter region E on the image plane 22. Further, in the example shown in FIG. 5, the second window member 15 having the same configuration and size as the window member 14 is arranged on the optical path of the first lens system 20. The second window member 15 is placed at a position symmetrical to the position of the window member 14 with respect to the first lens system 20. The image plane 22 is a plane on which the light rays emitted from the respective points of the emitter region E are converged into one point by the refraction of the first lens system 20 to form an image. The emitter region E and the image E'on the image plane 22 are at or near the conjugate position. In the embodiment of the present disclosure, the optical axis of the laser light L passing through the center of the emitter region E and the optical axis of the first lens system 20 coincide with each other. In the present disclosure, of the planes perpendicular to the optical axis of the first lens system 20, the plane passing through the center of the point where the light rays emitted from the center of the emitter region E converge by the first lens system 20 is referred to as the “image plane”. Define. When the screen is placed on the image plane 22, an image E'of the emitter region E is formed on the screen. However, since the screen is not actually arranged on the image plane 22, the image E′ functions as a virtual light source located in the free space. Such a virtual light source may be referred to as an intermediate image, redeveloped or transferred image of the emitter region E. The second window member 15 compensates for the influence of the window member 14 on the laser light L, and contributes to accurately reproducing the shape of the emitter region E by the shape of the image E′ formed on the image plane 22. The second window member 15 is not essential, but the first lens system 20 preferably has the second window member 15 or an optical member capable of exhibiting the function of the second window member 15.

The second lens system 30 converts the laser light L that has passed through the image plane 22 into a collimated beam B or a convergent beam and emits it. Since the second lens system 30 takes in light from the image (virtual light source) E′ of the emitter region E located on the image plane 22, the second lens system 30 is not subject to physical restrictions (interference) due to the structure of the package 10 and does not interfere with the second lens. The focal length of the system 30 can be shortened.

FIG. 5 shows a distance L0 from the end surface 12F of the LD 12 to the outer surface 14S of the window member 14 and a distance L2 from the image surface 22 to the second lens system 30. In the example shown in FIG. 5, the fast axis collimator lens FAC of the second lens system 30 is arranged so that L0>L2. In this way, the focal length of the second lens system 30 (specifically, the fast axis collimator lens FAC) can be shortened and the diameter of the collimated beam B can be reduced as compared with the case where physical restrictions are imposed by the structure of the package 10. “Distance” here means “optical distance”. The optical distance is a value obtained by integrating n·ds, which is the product of the line element ds and the refractive index n, along the path of the light ray, and is also called “optical distance” or “optical path length”. The distance L0 may differ depending on the refractive index of the window member 14 even if the window member 14 has the same thickness. The presence of window member 14 substantially increases the optical distance because the refractive index of window member 14 is higher than the refractive index of air (about 1.0). The thickness of the window member 14 is typically about 0.25 mm. When the window member 14 is formed of glass having a refractive index of 1.52, for example, the optical distance of the window member 14 alone can reach 0.38 (=0.25×1.52) mm. Further, since there is a predetermined gap between the LD 12 and the window member 14, the distance L0 may be 1.0 mm or more. The distance from the image plane 22 to the second lens system 30 is the closest to the image plane 22 among the surfaces of one or a plurality of optical elements such as lenses included in the second lens system 30. It means the optical distance between the surface and the image plane 22. In this embodiment, the distance L2 from the image plane 22 to the second lens system 30 corresponds to the “front focal length”, “working distance”, and “BFL: Back Focal Length” of the fast axis collimator lens FAC.

According to the present embodiment, the distance L2, that is, the “front focal length” of the fast axis collimator lens FAC can be set to 1.0 mm or less, typically 0.8 mm or less, and a value of 0.5 mm or less (for example, about 0). It is also possible to set it to 0.3 mm). In this way, the size of the collimated beam B in the fast axis (Y-axis) direction can be kept small while accommodating the LD 12 inside the sealed package 10. As a result, it becomes possible to improve long-term reliability without increasing the size of the optical system for focusing when performing spatial beam combining.

The 1st lens system 20 does not need to be comprised by one single lens, and may be comprised by a compound lens. Further, as shown in FIG. 6, the first lens system 20 may be a relay lens including an objective lens system 24 and an imaging lens system 26. By using the objective lens system 24 and the imaging lens system 26, an infinity correction optical system can be formed. The objective lens system 24 and the imaging lens system 26 may also be combined lenses. By adopting the combined lens, it is possible to reduce aberration and suppress deterioration of beam quality.

In the example of FIG. 6, the emitter region E of the LD 12 is located at the front focal point of the objective lens system 24. The image plane 22 is located at the rear focal point of the imaging lens system 26. In the embodiment of the present disclosure, the effective focal length F2 of the imaging lens system 26 is greater than or equal to the effective focal length F1 of the objective lens system 24. The effective focal length means the distance from the principal point of the lens to the focal point. Since the lateral magnification of the image formed on the image plane 22 is F2/F1, the size of the image E′ of the emitter region E on the image plane 22 is F2/F1 times the size of the emitter region E. When F2 is larger than F1, the enlarged image E′ of the emitter region E functions as a virtual light source. Here, the size of the virtual light source in the fast axis direction, that is, the beam diameter in the fast axis direction on the image plane 22 is 2×ω _y1 . Further, the divergence half angle in the fast axis direction of the beam emitted from the virtual light source (divergence half angle in the far field) is set to θ _y1 . On the other hand, the actual fast axis size of the emitter region E, that is, the beam diameter in the fast axis direction in the emitter region E is 2×ω _y0 . Further, the divergence half-angle in the fast axis direction of the beam emitted from the emitter region E (divergence half-angle in the far field) is defined as θ _y0 . Under the condition that the beam quality does not deteriorate, the relationship of ω _y0 ×θ _y0 =ω _y1 ×θ _y1 is established. Therefore, the F2 / F1 is greater than 1, than omega _y0 omega _y1 increases, theta _y1 is less than theta _y0. As a result, it is possible to reduce the numerical aperture of the second lens system 30 (the fast axis collimator lens FAC and the slow axis collimator lens SAC) and increase the effective focal length. The technical significance of this will be described later.

The second lens system 30 is not limited to an optical system that emits a collimated beam, but may be an optical system that emits a converged beam.

In the present embodiment, the distance L2 from the image plane 22 to the second lens system 30 is defined by the distance from the image plane 22 to the fast axis collimator lens FAC. Here, the distance from the image plane 22 to the fast-axis collimator lens FAC means an optical distance between the image plane 22 and the surface of the surface of the fast-axis collimator lens FAC closest to the image plane 22. To do. By using the fast-axis collimator lens FAC and the slow-axis collimator lens SAC without using the aspherical lens, it is possible to individually realize appropriate collimation for each of the fast-axis and the slow-axis. According to the embodiment of the present disclosure, by disposing the fast axis collimator lens FAC at a position close to the image plane 22, the effective focal length of the fast axis collimator lens FAC is shortened and the fast axis size of the collimated beam B is reduced. be able to.

In the embodiment of the present disclosure, when the second lens system 30 includes the fast axis collimator lens FAC and the slow axis collimator lens SAC which are sequentially arranged from the image plane 22 side, the effective focal length EFL of the fast axis collimator lens FAC is set. By setting it to 1.0 mm or less, the fast axis size of the collimated beam B can be set to 1.0 mm or less (for example, about 0.8 mm). When the fast axis size of the collimated beam B is small, an optical system and a device (beam combiner) for spatially coupling the plurality of collimated beams B can be downsized.

An aperture stop may be arranged at the position of the image plane 22. Unwanted light in the peripheral portion of the emitter image E'which functions as a virtual light source can be blocked by the aperture stop. When the collimated beam B is incident on the optical fiber, the interference light unnecessary for fiber coupling (interference light formed outside the air disk) is removed by the function of the aperture stop.

Laser Light Source Module Next, an embodiment of a laser light source module according to the present disclosure will be described with reference to FIGS. 7A, 7B, and 7C. FIG. 7A is a schematic top view of the laser light source module 200 according to the present embodiment as viewed from the direction normal to the XZ plane, FIG. 7B is a schematic side view viewed from the direction normal to the YZ plane, and FIG. 7C is a view of the XY plane. It is a typical front view seen from a normal line direction. The illustrated configuration is housed in a housing (not shown).

The illustrated laser light source module 200 includes a plurality of laser light sources 100A, 100B, 100C and a beam combiner 120. Each of the plurality of laser light sources 100A, 100B, 100C is the light source unit 100 described above. Hereinafter, for simplicity, the laser light sources 100A, 100B, and 100C may be collectively referred to as "light source unit 100". The number of light source units 100 included in one laser light source module 200 is arbitrary. In this example, the number of light source units 100 is three, but typically four or more. FIG. 8 is a perspective view schematically showing another configuration example including nine light source units 100. It is possible to increase the light output and light intensity of the combined beam in proportion to the number of the light source units 100. In order to fill the limited space with a large number of collimated beams to increase the filling rate, the size of the fast axis of the collimated beam is reduced to shorten the center-to-center pitch S of the collimated beams B in the Y-axis (fast axis) direction. Preferably.

Although the collimated beam B is simply described as perfect parallel light in the drawing, the actual collimated beam B diverges at a predetermined divergence angle after reaching the minimum beam radius at the beam waist. Therefore, in the example shown in FIG. 8, when the number of the light source units 100 becomes too large, the optical path of the collimated beam B from the light source unit 100 located at a position distant from the converging optical system 160 becomes long, and the beam length becomes large. Large diameter may diverge. As an example, when the effective focal length of the fast axis collimator lens FAC is 0.3 mm, the distance from the fast axis collimator lens FAC to the beam waist of the collimated beam B is, for example, about 50 mm. In such an example, if the number of light source units 100 exceeds 10 and increases, the maximum optical path length greatly exceeds 50 mm. As a result, some of the divergence of the collimated beam B cannot be ignored, and it may be difficult to properly focus the optical fiber having a small core size. For this reason, the number of collimated beams B to be combined by spatial beam combining is not necessarily as high as possible simply, and is preferably set in an appropriate range according to the conditions.

The beam combiner 120 spatially combines the plurality of collimated beams B emitted from the plurality of light source units 100. In this embodiment, the collimated beams B emitted from the respective light source units 100 have substantially the same wavelength (for example, about 465 nm±10 nm), but their phases are not synchronized with each other. Therefore, the plurality of collimated beams B are incoherently combined.

In the present embodiment, the laser light source module 200 includes a support base 140 that supports the plurality of light source units 100 such that the distances (heights) H from the reference plane Ref to the centers of the plurality of collimated beams B are different. Prepare As shown in FIG. 7B, the support 140 has a mounting surface 140T having a plurality of steps. The center-to-center pitch S of the collimated beam B in the Y-axis (fast axis) direction corresponds to the size of the step on the mounting surface 140T of the support 140. The center-to-center pitch S can be set within a range of, for example, 200 μm or more and 350 μm, but the steps are exaggerated and greatly illustrated in FIGS. 7B, 7C, and 8 for ease of understanding. As shown in FIG. 7A, the light source units 100 are arranged at the center-to-center pitch P along the Z-axis direction.

The beam combiner 120 in the present embodiment includes a mirror array having a plurality of mirrors M that respectively reflect a plurality of collimated beams B. Specifically, the mounting surface 140T of the support 140 supports a number of mirrors M corresponding to the number of light source units 100 at different heights (level positions). The position and orientation of each mirror M is aligned so as to reflect the corresponding collimated beam B and direct it toward the converging optical system 160. In a typical example, the mirror M rotates the collimated beam B 90 degrees about an axis parallel to the Y axis. Thus, the array of the mirrors M of the present embodiment propagates the plurality of reflected collimated beams B along the plane (YZ plane) perpendicular to the reference plane Ref. The mirror M may be fixed to a housing wall (not shown), or may be fixed via a component capable of adjusting the position and orientation of each mirror M. It is desirable that the reflecting surface of the mirror M be formed of a multilayer film that selectively has a high reflectance at the wavelength of the incident collimated beam B.

The center-to-center pitch S of the collimated beam B in the Y-axis direction is larger than the size of each mirror M in the Y-axis direction. In the typical example, the size of each mirror M in the Y-axis direction is set to twice or more the Y-axis direction radius ω _y2 of each collimated beam B. Strictly speaking, ω _y2 is a value at the beam waist of the collimated beam B, but since the divergence half-angle is sufficiently small, the Y-axis direction radius of the collimated beam B on the optical path in this example is approximately ω _y2 . You may approximate it as equal. In the present embodiment, S>2×ω _y2 holds. When ω _y2 is, for example, 100 μm, S can be set to, for example, 300 μm (=2.5×ω _y2 ). The smaller the Y-axis direction radius ω _y2 of each collimated beam B, the smaller the center-to-center pitch S can be made. Here, when the light source unit 100Q as shown in FIG. 3B is adopted instead of the light source unit 100 in this embodiment, the Y-axis direction radius ω _y2 of each collimated beam B reaches about 1 mm. Therefore, the step size S also needs to be about 1 mm or more, and the beam diameter after spatial beam combination becomes too large. Further, such a problem becomes more remarkable as the number of light source units 100 increases, as shown in FIG. However, this problem can be solved by using the light source unit 100 in this embodiment.

When determining the center-to-center pitch S of the collimated beams B in the Y-axis direction, it is not necessary to worry about physical interference between the light source units 100. On the other hand, the center-to-center pitch P in the Z-axis direction is determined so that two adjacent light source units 100 do not physically interfere with each other.

The beam combiner 120 includes an optical system 160 that converges the plurality of collimated beams B that are respectively reflected by the plurality of mirrors M. The optical system 160 in the present embodiment optically couples the plurality of collimated beams B to an optical fiber (not shown). The reflecting surface of the mirror M does not need to be flat. The mirror M may have at least a part of the converging function of the optical system 160. The beam combiner 120 may have an optical component other than the mirror M, for example, a filter having wavelength selectivity.

The configurations shown in FIGS. 7A, 7B, 7C, and 8 can be housed in a housing (not shown). The case itself is sometimes called a package, but compared to the above-mentioned semiconductor laser package, it has a large number of parts inside, and achieves a clean level that sufficiently suppresses the light dust collection effect and maintains airtightness. It's difficult.

Hereinafter, with reference to FIGS. 9A and 9B, a configuration example of the optical system 160 that couples the plurality of collimated beams B will be described. 9A and 9B each show a configuration example of the optical system 160 that converges n collimated beams B arranged at the center-to-center pitch S along the fast axis (Y-axis) direction. The difference between the example of FIG. 9A and the example of FIG. 9B is the difference in the fast axis collimator lens FAC.

In the example shown, n is an odd number greater than or equal to 3, but n may be an even number. Further, for the sake of simplicity, as the collimated beam B, completely parallel rays are shown in the drawing. However, as described above, the actual collimated beam B reaches a minimum beam radius at the beam waist and then has a predetermined divergence. Divergence at an angle. When the total size of the n collimated beams B incident on the optical system 160 in the Y-axis direction is 2×R _TY , the relationship of 2×R _TY =S×(n−1)+2×ω _y2 is established. This relationship can be rewritten as R _TY =S×(n−1)/2+ω _y2 . Since the n collimated beams B are arranged linearly along the fast axis (Y axis) direction, the overall size of the n collimated beams B in the X axis direction is the X of the individual collimated beams B. It is equal to the size in the axial direction 2×ω× ₂ .

The optical system 160 in FIGS. 9A and 9B includes a slow-axis converging lens SAF and a fast-axis converging lens FAF in order from the side closer to the position (rear focus) Q of the convergence point. These lenses are cylindrical lenses. Here, it is assumed that the Z axis (dotted line) coincides with the optical axis of the optical system 160. The fast axis converging lens FAF converges all the collimated beams B in a plane (YZ plane) including the Z axis and the fast axis direction (Y axis). The slow axis converging lens SAF converges each collimated beam B in a plane (XZ plane perpendicular to the paper surface) including the Z axis and the slow axis direction (X axis).

The fast-axis converging lens FAF and the slow-axis converging lens SAF are arranged so that their rear focal points coincide with each other. The Y-axis direction radius ω _{y3 at} the convergent position Q of the combined laser beam has a value obtained by multiplying the Y-axis direction radius ω _y1 of the virtual light source by a magnification (EFL _FAF /EFL _FAC ). Here, EFL _FAC is the effective focal length of the fast-axis collimator lens FAC, and EFL _FAF is the effective focal length of the fast-axis converging lens FAF.

As described above, in the embodiment of the present disclosure, when the effective focal length F2 of the imaging lens system 26 is made longer than the effective focal length F1 of the objective lens system 24, the lateral magnification of the image formed on the image plane 22 becomes Since it is F2/F1, the size of the image E′ of the emitter region E on the image plane 22 is enlarged by F2/F1 times the actual size of the emitter region E. Further, theta _y1 (divergence half-angle in the far field) fast-axis direction divergence half-angle is emitted from the virtual light source beam as F2 / F1 is large, small. When the divergence half angle in the fast axis direction (divergence half angle in the far field) θ _{y1 of} the beam emitted from the virtual light source becomes small, the numerical aperture of the fast axis collimator lens FAC can be made small and the effective focal length can be made long. .. In the configuration example of FIG. 9B, θ _y1 is relatively smaller than that of the configuration example of FIG. 9A. When the fast axis collimator lens FAC having a longer effective focal length EFL _FAC is adopted, the lateral magnification (EFL _FAF /EFL _FAC ) at the convergence position Q by the fast axis collimator lens FAC and the fast axis convergent lens FAF becomes smaller. As described above, when the lateral magnification at the convergent position Q becomes small, the positional deviation tolerance of the convergent beam spot with respect to the core of the optical fiber can be increased.

As an example, when ω _y1 =2.0 μm, EFL _FAC =0.3 mm, and EFL _FAF =10.0 mm, ω _y3 =66.7 μm. When ω _y1 =4.0 μm, EFL _FAC =0.6 mm, and EFL _FAF =10.0 mm, ω _y3 =66.7 μm. Further, when the effective focal length of the slow axis collimator lens SAC is EFL _SAC and the effective focal length EFL _SAF of the slow axis converging lens SAF, the radius ω _x3 in the X-axis direction at the convergent position Q of the combined laser beam is X of the virtual light source. It has a value obtained by multiplying the axial radius ω _x1 by a magnification (EFL _SAF /EFL _SAC ). For example, when ω _x1 =80 μm, EFL _SAC =5.0 mm, and EFL _SAF =4.0 mm, ω _x3 =64 μm.

According to this embodiment, for example, a laser beam can be focused on a multimode optical fiber having a numerical aperture of about 0.2 and a core diameter of 100 μm. Since the n laser beams are combined incoherently, the light intensity increases n times. In the configuration of FIG. 3B, since S and R _TY increase, it is necessary to upsize the converging optical system 160.

10A, 10B, and 10C schematically show beam cross-sectional shapes when five, nine, and nine×2 rows of collimated beams B are incident on the fast axis converging lens FAF. .. The form of FIG. 10C is obtained by arranging a plurality of light source units 100 in two rows, as shown in FIG.

The arrangement of the light source units 100 is not limited to the example described above. FIG. 12 is a schematic top view showing still another example. The beams output from the plurality of light source units 100 may be arranged in three rows. Further, the plurality of light source units 100 and/or the mirrors M need not be parallel to each other and may be inclined.

According to the embodiment of the present disclosure, since the LD 12 is housed in the package, the decrease in the optical output of the LD 12 due to the light collecting effect that can be caused by the high-power short-wavelength laser beam is suppressed, and the reliability is improved. To do. Further, since it becomes possible to combine a plurality of collimated beams B with a high spatial density, it is possible to effectively increase the optical output. Furthermore, since the increase in the size of the fast axis of the collimated beam B can be suppressed, the degree of freedom in the spatial arrangement of the light source unit 100 is increased, and a large number of collimated beams B can be arranged closely. As a result, it becomes possible to couple a high-power laser beam into an optical fiber with high efficiency.

In the above embodiment, one LD 12 is accommodated in each package 10, but a plurality of LDs 12 may be accommodated in each package 10. Further, in each embodiment, each LD 12 has one emitter region E, but one LD 12 may have a plurality of emitter regions E. As described above, even if a plurality of emitter regions E (emitter arrays) are located inside one package 10, the effects of the embodiments of the present disclosure can be obtained. That is, if the virtual light source is formed in the free space by transferring the image of the emitter array located inside each package 10 onto the image plane 22 of the first lens system 20, the package structure is not limited and It is possible to design the two-lens system 30.

Direct Diode Laser Device Next, with reference to FIG. 13, an embodiment of a direct diode laser (DDL) device according to the present disclosure will be described. FIG. 13 is a diagram showing a configuration example of the DDL device 1000 in the present embodiment.

The illustrated DDL device 1000 includes four laser light source modules 200, a processing head 400, and an optical transmission fiber 300 that connects the laser light source module 200 to the processing head 400. The number of laser light source modules 200 is one or more, and is not limited to four.

Each laser light source module 200 has the same configuration as that described above. The number of LDs mounted on each laser light source module 200 is not particularly limited, and is determined according to the required light output or irradiance. The wavelength of the laser light emitted from each LD can also be selected according to the material to be processed. For example, when processing copper, brass, aluminum, etc., LD which belongs to the range whose center wavelength is 350 nm or more and 550 nm or less can be used suitably. The wavelengths of the laser lights emitted from the LDs do not have to be the same, and laser lights having different central wavelengths may be superimposed. Further, the effects of the present invention can be obtained even when using a laser beam having a central wavelength outside the range of 350 nm to 550 nm.

In the illustrated example, the optical fiber 220 extending from each of the plurality of laser light source modules 200 is coupled to the optical transmission fiber 300 by the optical fiber coupler 230. The processing head 400 converges and irradiates the object 500 with the laser beam emitted from the tip of the optical transmission fiber 300 by an optical system (not shown). In the case where one DDL device 1000 includes M laser light source modules 200 and each laser light source module 200 has N LDs, if the optical output of one LD is P watts, A laser beam with a maximum optical power of P×N×M watts can be focused on the object 500. Here, N is an integer of 2 or more, and M is a positive integer. For example, if P=10 watts, N=9, and M=12, a light output exceeding 1 kilowatt is realized.

According to the present embodiment, since the LD in the laser light source module is housed in the semiconductor laser package, the decrease in light output due to the light collecting effect is suppressed and the reliability is improved. Further, since a large number of collimated beams having a small beam diameter can be filled in the limited space, a high optical output can be achieved with a small device, and the optical fiber can be easily coupled.

Fiber Laser Device Next, an embodiment of a fiber laser device according to the present disclosure will be described with reference to FIG. 14. FIG. 14 is a diagram showing a configuration example of the fiber laser device 2000 in the present embodiment.

The illustrated fiber laser device 2000 includes a laser light source module 200 that functions as an excitation light source, and a rare earth-doped optical fiber 600 that is excited by the excitation light emitted from the laser light source module 200. In the illustrated example, the optical fiber 220 extending from each of the plurality of laser light source modules 200 is coupled to the rare earth-doped optical fiber 600 by the optical fiber coupler 230. The rare earth-doped optical fiber 600 is sandwiched by a pair of fiber Bragg gratings that define a resonator. When the rare earth-doped optical fiber 600 is doped with Yb ions, the laser light source module 200 that generates excitation light having a wavelength of, for example, 915 nm is used. In the laser light source module 200 according to the embodiment of the present disclosure, since the LD is housed in the semiconductor laser package, as described above, particularly when the LD that emits blue or green laser light is adopted, an excellent effect is exhibited. You can In addition, for example, when the rare earth-doped optical fiber 600 formed of fluoride glass doped with praseodymium (Pr) is used, it is possible to realize visible light laser oscillation by blue excitation light. The laser light source module 200 according to the embodiment of the present disclosure is useful as such an excitation light source.

The processing head 400 converges the laser beam emitted from the tip of the rare earth-doped optical fiber 600 onto the object 500 by an optical system (not shown) and irradiates it.

Thus, in the laser light source module of the present disclosure, in a non-limiting and exemplary embodiment, a plurality of laser light sources, each of which is the light source unit, and a plurality of collimated beams emitted from the plurality of laser light sources, respectively. And a beam combiner for spatially coupling the two.

In one embodiment, a support is provided that supports the plurality of laser light sources so that the heights from the reference plane to the centers of the plurality of collimated beams are different from each other. The beam combiner is a mirror array having a plurality of mirrors that respectively reflect the plurality of collimated beams, the mirror array propagating the plurality of reflected collimated beams along a plane perpendicular to the reference plane; , An optical system for converging the plurality of collimated beams reflected by the plurality of mirrors.

Further, the direct diode laser device of the present disclosure, in a non-limiting and exemplary embodiment, propagates at least one laser light source module and a laser beam emitted from the laser light source module, and emits the laser beam. And a processing head coupled to the optical fiber for irradiating an object with the laser beam emitted from the optical fiber.

Further, the fiber laser device of the present disclosure includes, in a non-limiting and exemplary embodiment, at least one laser light source module and a rare earth-doped optical fiber excited by a laser beam emitted from the laser light source module. Prepare

INDUSTRIAL APPLICABILITY The light source unit of the present disclosure can be used in various applications in which the fast axis size of a collimated beam or a converged beam is required to be small. In particular, it can be used to combine a plurality of laser beams to realize a high-power laser beam. Further, the laser light source module and the direct diode laser device of the present disclosure are used in industrial fields where a high-power laser light source is required, for example, cutting, drilling, local heat treatment, surface treatment, metal welding, and 3D printing of various materials. It can be used for. Further, the laser light source module of the present disclosure can be used for applications other than the DDL device, for example, as an excitation light source for a fiber laser device.

10... Semiconductor laser package, 12... LD, 14... Window member, 20... First lens system, 22... Image plane, 24... Objective lens system, 26... Connection Image lens system, 30... Second lens system, 100... Light source unit, 120... Beam combiner, 140... Support, 160... Converging optical system, 300... Optical transmission fiber, 400 ... Processing head, 1000... Direct diode laser (DDL) device, B... Beam, M... Mirror, FAC... Fast axis collimator lens, SAC... Slow axis collimator lens, FAF. ..Fast axis converging lens, SAF... Slow axis converging lens

Claims (8)

A semiconductor laser package, which is a sealed semiconductor laser package, including a laser diode having an emitter region for emitting laser light on an end surface thereof, and a window member for transmitting the laser light,
A first lens system which receives the laser beam transmitted through the window member and forms an image of the emitter region on an image plane;
A second lens system that converts the laser light that has passed through the image plane into a collimated beam or a convergent beam and emits it;
A light source unit. The light source unit according to claim 1, wherein a distance from the image surface to the second lens system is shorter than a distance from the end surface of the laser diode to an outer surface of the window member. The light source unit according to claim 1, wherein the first lens system includes an objective lens system and an imaging lens system. The emitter region of the laser diode is located at the front focus of the objective lens system,
The image plane is located at a rear focal point of the imaging lens system,
The light source unit according to claim 3, wherein the effective focal length of the imaging lens system is equal to or more than the effective focal length of the objective lens system. The light source unit according to claim 3 or 4, wherein the objective lens system and the imaging lens system are each a combination lens. The second lens system includes a fast axis collimator lens and a slow axis collimator lens, which are sequentially arranged from the image plane side,
6. The light source unit according to claim 2, wherein the distance from the image surface to the second lens system is defined by the distance from the image surface to the fast axis collimator lens. The light source unit according to claim 1, wherein the distance from the image plane to the second lens system is 1.0 millimeter or less. The second lens system includes a fast axis collimator lens and a slow axis collimator lens, which are sequentially arranged from the image plane side,
The effective focal length of the fast axis collimator lens is 1.0 mm or less,
The light source unit according to claim 1, wherein a fast axis size of the collimated beam is 1.0 mm or less.

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