Semiconductor laser element and laser module provided with the same, laser oscillator, and laser processing device

Abstract

To provide a semiconductor laser element capable of easily generating external resonance and obtaining a high-output laser beam.SOLUTION: A laser diode bar 10 has a plurality of emitters 20 spaced apart from each other along a longitudinal direction. The emitter 20 has a front end surface and a rear end surface, and a laser beam LBE is emitted from each of the front end surfaces of the plurality of emitters 20. A first end surface coating layer 11 is provided on the front end surface of the emitter 20, and a second end surface coating layer 12 is provided on the rear end surface. An oxide film 13 containing a silicon-oxygen compound is formed on a first portion 11a that is a top surface of the first end surface coating layer 11 and through which the laser beam LBE passes. Hardness of the oxide film 13 is lower than that of SiO2.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a semiconductor laser element, and a laser module, a laser oscillator, and a laser processing apparatus each including the semiconductor laser element. [Background technology]

[0002] In recent years, expectations for laser processing have been rising for various materials such as copper, gold, and resin. For example, in the automobile industry, motorization, miniaturization, high rigidity, improved design freedom, and improved productivity are required, and expectations for laser processing are high. To achieve highly productive processing, a laser light source that can generate a highly efficient and high-power laser light is required. A semiconductor laser element is known as a laser light source suitable for this requirement. In particular, to increase the output of laser light, a laser module equipped with a laser diode bar having a plurality of emitters that emit laser light is useful.

[0003] However, when a semiconductor laser element emits a high-power laser beam, contaminants may adhere to the light-emitting end face of the semiconductor laser element and accumulate as deposits. A typical contaminant is a siloxane compound having a Si-O-Si bond. When a siloxane compound in the atmosphere is irradiated with a laser beam, a photodecomposition reaction occurs, and the decomposition product adheres to the light-emitting end face and becomes a deposit. This photodecomposition reaction progresses more as the output of the laser beam is higher and the wavelength of the laser beam is shorter. Therefore, in a semiconductor laser element that emits a high-power and short-wavelength laser beam, for example, a blue laser beam, the thickness of the deposits accumulated on the light-emitting end face becomes large.

[0004] When the thickness of the deposit increases, the deposit absorbs a portion of the laser light, reducing the output of the laser light that can be extracted to the outside. Also, the optical characteristics of the laser light degrade when it passes through the deposit. Furthermore, the deposit absorbs the laser light and generates heat, increasing the temperature of the light-emitting end face, reducing the operational reliability of the semiconductor laser element. In extreme cases, part of the light-emitting end face melts, causing the semiconductor laser element to break down.

[0005] In view of this, various configurations have been proposed to reduce adhesion of contaminants to the light-emitting end face and suppress the generation of deposits (see, for example, Patent Documents 1 to 4).

[0006] Incidentally, in laser processing, in order to miniaturize and increase the efficiency of a laser light source, a technology is widely used in which multiple laser modules as described above are used to combine the laser light emitted from each of them, thereby increasing the output of the laser light output from the laser light source.

[0007] To obtain high-power laser light, the laser lights emitted from a plurality of emitters are combined into one combined laser light, and the combined laser lights emitted from a plurality of laser diode bars are further combined into one processing laser light. In generating such processing laser light, a laser module using wavelength synthesis and wavelength locking technology of laser light has been proposed (see, for example, Patent Document 5). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2003-289010 A [Patent Document 2] JP 2004-040051 A [Patent Document 3] JP 2004-014820 A [Patent Document 4] JP 2009-021548 A [Patent Document 5] Patent No. 5832455 Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, in the laser module disclosed in Patent Document 5, an external resonator is formed between a laser diode bar and an external resonator mirror to perform laser oscillation.

[0010] On the other hand, a coating layer having a predetermined thickness and refractive index is formed on the light-emitting end face of the semiconductor laser element in order to reduce the reflectance of the laser light. However, in order to set the reflectance of the coating layer to a desired value, it is necessary to precisely control the thickness. In addition, since the reflectance changes greatly when the thickness fluctuates, there is a problem that if the thickness deviates from the desired range, it becomes difficult for external resonance to occur.

[0011] The present disclosure has been made in consideration of these points, and its purpose is to provide a semiconductor laser element that, by defining the characteristics of the deposit adhering to the light-emitting end face, makes external resonance more likely to occur and produces high-output laser light, as well as a laser module, laser oscillator, and laser processing apparatus that are equipped with the same. [Means for solving the problem]

[0012] In order to achieve the above object, a semiconductor laser element according to the present disclosure is a semiconductor laser element having an emitter that emits laser light, the emitter having a front end face that is an end face from which the laser light is emitted, and a rear end face opposite the front end face, a first end face coating layer is provided on the front end face and a second end face coating layer is provided on the rear end face, an oxide film containing a compound of silicon and oxygen is formed on an outermost surface of the first end face coating layer, which is a first portion through which the laser light transmits, and the hardness of the oxide film is lower than the hardness of SiO2.

[0013] The laser module according to the present disclosure at least comprises the semiconductor laser element, an optical coupling element that combines the multiple laser beams emitted from each of the multiple emitters, an external resonator mirror that reflects the laser beam combined by the optical coupling element toward the optical coupling element, and a housing that accommodates one or more of the semiconductor laser elements, the optical coupling element, and the external resonator mirror, and is characterized in that an external resonator is formed between the external resonator mirror and the second end face coating layer formed on the emitter, and the combined laser beam combined by the optical coupling element is emitted to the outside of the housing.

[0014] The laser oscillator of the present disclosure is a laser oscillator comprising at least the laser module, a control unit, and a power supply, wherein one or more of the laser modules are mounted, the control unit controls the laser oscillation of the laser oscillator, and the power supply supplies power to the laser module for performing the laser oscillation.

[0015] The laser processing apparatus of the present disclosure comprises at least the laser oscillator, an optical fiber, and a laser head, wherein the optical fiber receives the processing laser light emitted from the laser oscillator and guides it to the laser head, and the laser head is attached to the output end of the optical fiber, receives the processing laser light guided by the optical fiber, and irradiates it toward a workpiece. Effect of the Invention

[0016] According to the present disclosure, external resonance is made easier to occur, and high-output laser light can be obtained. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a laser module according to a first embodiment. [Diagram 2] FIG. 1 is a schematic diagram for explaining the principle of wavelength synthesis. [Diagram 3] FIG. 2 is a perspective view of a laser diode bar. [Figure 4] FIG. 2 is a schematic diagram of an emitter as viewed from the front. [Diagram 5] 2 is a schematic cross-sectional view of the vicinity of a light-emitting end surface of an emitter. FIG. [Figure 6] FIG. 11 is a diagram showing the relationship between the thickness and hardness of an oxide film and the likelihood of external resonance occurring. [Figure 7] FIG. 11 is a schematic configuration diagram of a laser processing device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0019] (Embodiment 1) [Explanation of the laser module configuration and wavelength synthesis principle] Fig. 1 is a schematic diagram of a laser module according to embodiment 1. Fig. 2 is a schematic diagram for explaining the principle of wavelength combining.

[0020] As shown in Fig. 1, the laser module 60 includes a plurality of laser diode bars (semiconductor laser elements) 10, a diffraction grating 30, an external cavity mirror 40, and a housing 50. The laser module 60 shown in Fig. 1 includes a plurality of other members in addition to the above-mentioned members, such as a laser beam LB E The laser diode bars 10 have collimating lenses and the like for collimating the spread of the laser diode bars 10 in the fast axis direction and the slow axis direction, but for the sake of convenience, these members are not shown and are not described. Also, the number of laser diode bars 10 is different from the actual number.

[0021] 1, a plurality of laser diode bars 10, a diffraction grating 30, and an external resonator mirror 40 are arranged inside a housing 50 while maintaining a predetermined positional relationship with each other. The external resonator mirror 40 is provided in the housing 50, covering a light exit window (not shown) provided in the housing 50. The external resonator mirror 40 may be provided inside the housing 50, between the diffraction grating 30 and the light exit window.

[0022] The laser diode bar 10 has a plurality of emitters 20, and each of the emitters 20 emits laser light LB. E (See FIG. 3.) The configurations of the laser diode bar 10 and the emitter 20 will be described in detail later. In addition, in FIG. 1, the illustration and description of the submount that supports the laser diode bar 10 and the support member that supports the submount on which the laser diode bar 10 is mounted are omitted.

[0023] As shown in FIGS. 1 and 2, in one laser diode bar 10, a plurality of laser beams LB are emitted from a plurality of emitters 20. E The beams travel toward the diffraction grating 30 after their expansion in the fast axis direction and the slow axis direction is collimated and their rotation direction is changed.

[0024] The diffraction grating 30 reflects a plurality of laser beams LB E Each laser beam LB E The diffraction grating 30 diffracts the laser beams LB and directs them toward the external cavity mirror 40. E The diffraction grating 30 transmits each laser beam LB E It may be of a type that reflects light.

[0025] At this time, the diffraction grating 30 reflects each laser beam LB E The optical axes of the laser beams LB are close to each other and parallel to each other. E are diffracted, respectively.

[0026] The external cavity mirror 40 reflects the incident laser beams LB E 1 and 2. The external cavity mirror 40 transmits a part of the laser diode bars 10 and reflects the remaining part toward the diffraction grating 30. In this manner, an external cavity is formed between the external cavity mirror 40 and each of the laser diode bars 10. This will be described in further detail below.

[0027] As shown in FIG. 2, each laser beam LB emitted from the laser diode bar 10 E After being diffracted by the diffraction grating 30, the laser light LB is incident on the external cavity mirror 40. E A part of the laser light LB is transmitted through the diffraction grating 40, while the remaining part is reflected toward the diffraction grating 40 and then returns to the laser diode bar 10. Most of this reflected return light passes through the first end face coating layer 11 (see FIG. 3) of the laser diode bar 10 and reaches the second end face coating layer (reflective layer; see FIG. 3) 12. Eis reflected by the second end face coating layer 12 and emitted again from the first end face coating layer 11 to the outside of the laser diode bar 10.

[0028] Laser light LB emitted from each emitter 20 of the laser diode bar 10 E Of these, only light having a wavelength (hereinafter referred to as a lock wavelength) that satisfies the diffraction condition of the diffraction grating 30 and is reflected by the external cavity mirror 40 is fed back to the original emitter 20, thereby forming an external cavity between the second end face coating layer 12 of the laser diode bar 10 and the external cavity mirror 40, and laser light LB is emitted from the laser diode bar 10, specifically, from each of the multiple emitters 20. E will be output.

[0029] The lock wavelength of each emitter 20 is λ L , the period of the diffraction grating 30 is d, the angle of incidence is α, the angle of emergence is β, and the order is m, then the lock wavelength λ L is expressed by equation (1).

[0030] d(sinα+sinβ)=mλ L ...(1) Generally, the order of the diffraction grating 30 is m=1.

[0031] For example, in the laser diode bar 10, the emitters 20 are formed so that the angle of incidence α with respect to the incident surface of the diffraction grating 30 changes for each position of the emitters 20. In this case, the lock wavelength of the emitters 20 formed in the laser diode bar 10 changes stepwise from one end of the laser diode bar 10 to the other end.

[0032] Each emitter 20 can oscillate by external resonance only when the inherent gain wavelength intensity of the laser diode bar 10 is equal to or greater than a predetermined value. gTherefore, in the laser module 60 of this embodiment, the gain peak wavelength λ of each emitter 20 is oscillated at a lock wavelength within a predetermined range, and is not oscillated at a lock wavelength outside the predetermined range. g The upper and lower limit ranges are the lock wavelengths λ of the emitters 20 at both ends of the laser diode bar 10. L Difference Δλ L_bar The optical design of the laser diode bar 10 and each emitter 20 is performed so that the lock wavelength λ of the emitters 20 at both ends falls within the range. L Difference Δλ L_bar varies with the distance between the laser diode bar 10 and the diffraction grating 30.

[0033] Laser light LB emitted from each emitter 20 of the laser diode bar 10 E The positional relationship between the laser diode bar 10 and the diffraction grating 30 is determined so that the optical axes of the laser diode bars 10 and the diffraction grating 30 overlap each other when they pass through the diffraction grating 30.

[0034] That is, the laser light LB emitted from each of the multiple emitters 20 provided on the multiple laser diode bars 10 E are made to overlap each other when they are incident on the external cavity mirror 40. In this way, the multiple laser beams LB E The laser light LB emitted from each of the multiple emitters 20 provided on the multiple laser diode bars 10 is superimposed and combined, which is called wavelength synthesis. E There is one combined laser beam (module laser beam LB M ) and is emitted to the outside of the laser module 60.

[0035] [Laser diode bar and emitter configuration] Fig. 3 is a perspective view of a laser diode bar, Fig. 4 is a schematic diagram of an emitter as viewed from the front, and Fig. 5 is a schematic cross-sectional view of the vicinity of the light-emitting end face of the emitter.

[0036] In the following description, the laser light LB emitted from each of the multiple emitters 20 provided on the laser diode bar 10 is E The direction in which the laser beam LB travels is sometimes called the X direction, and the direction in which the emitters 20 are arranged is sometimes called the Y direction. The direction perpendicular to the X direction and the Y direction is sometimes called the Z direction. E The Y direction corresponds to the fast axis direction, and the Y direction corresponds to the slow axis direction. The fast axis and the slow axis will be explained later.

[0037] The Z direction is also the stacking direction of the semiconductor layers in the emitter 20. In the X direction, the laser light LB E The side on which the output end face of the laser beam LB is provided is sometimes called the front or front side. E The exit end face of the laser beam splitter is called the front end face. The side on which the rear end face, which faces the front end face in the X direction, is provided is sometimes called the rear, back, or rear side.

[0038] In this specification, "orthogonal," "parallel," or "the same" means orthogonal, parallel, or the same, including the processing tolerances of the laser diode bar 10 and its components, and does not mean that the objects being compared are orthogonal, parallel, or the same in the strict sense.

[0039] 3, the laser diode bar 10 has emitters 20 spaced apart from one another along the longitudinal direction, i.e., the Y direction. The front end face of the laser diode bar 10 is covered with a first end face coating layer 11. The rear end face of the laser diode bar 10 is covered with a second end face coating layer 12.

[0040] The first end face coating layer 11 is E The second end face coating layer (reflective layer) 12 is adjusted to have a reflectance of several percent or less with respect to the laser light LB. EWhen the emitter 20 oscillates, the laser light LB E is emitted forward. Note that, in order to adjust the reflectance, both the first end face coating layer 11 and the second end face coating layer 12 are formed by laminating a plurality of dielectric films having mutually different refractive indices, but detailed explanation of the configuration will be omitted.

[0041] As shown in FIG. 3, the laser beams LB emitted from the emitters 20 of the laser diode bar 10 are E In the laser diode bar 10, the cross section cut by a virtual plane perpendicular to the optical axis at a location more than a predetermined distance away (also called a far field pattern (FFP)) is elliptical. The long axis direction (long diameter direction) of this ellipse is called the fast axis direction. Note that the fast axis and the laser beam LB E The direction perpendicular to the optical axis of each of the ellipses is called the slow axis direction (the short axis direction (minor axis direction) that is the short side direction of the ellipse). The fast axis is an axis perpendicular to the stacking direction of the semiconductor layers in the emitter 20, and the slow axis is an axis parallel to the stacking direction.

[0042] The emitter 20 is composed of a plurality of nitride semiconductor layers stacked in the Z direction. Specifically, as shown in FIG. 4, the emitter 20 has an n-type substrate 21, an n-type cladding layer 22, an active layer 23, a p-type cladding layer 24, and a p-type contact layer 25. An n-side electrode 27 is formed on the back surface of the n-type substrate 21. A p-side electrode 28 is formed on the surface of the p-type contact layer 25. In this embodiment, the n-type substrate 21, the n-type cladding layer 22, the active layer 23, the p-type cladding layer 24, and the p-type contact layer 25 are all composed of nitride semiconductor materials. In addition, the laser light LB E The wavelength range is from ultraviolet to blue. In this specification, the term "ultraviolet to blue wavelength range" refers to a wavelength range of 350 nm or more and 460 nm or less.

[0043] The p-type cladding layer 24 and the p-type contact layer 25 are processed into a linear stripe shape extending in the Z direction, and may be collectively referred to as the stripe portion 20a. An insulating layer 26 is formed so as to cover the surfaces of the stripe portion 20a and the p-type cladding layer 24, except for the p-side electrode 28. The insulating layer 26 prevents current from flowing to the active layer 23 from the p-type cladding layer 24 where the p-side electrode 28 is not provided, thereby realizing current confinement to the active layer 23 in the Y direction.

[0044] The p-side electrode 28 has an ohmic electrode 28a, an adhesion layer 28b, and a bonding electrode 28c. The ohmic electrode 28a is in contact with the p-type contact layer 25 and is in ohmic contact with the p-type contact layer 25. The adhesion layer 28b adheres the bonding electrode 28c to the insulating layer 26. The bonding electrode 28c is bonded to a submount (not shown). In other words, the laser diode bar 10 is a so-called junction-down type semiconductor laser element mounted on a submount so that the active layer 23, which is a light-emitting layer, is close to the submount. However, the present invention is not limited to this, and the laser diode bar 10 may be a so-called junction-up type semiconductor laser element mounted on a submount so that the active layer 23, which is a light-emitting layer, is away from the submount.

[0045] When a voltage equal to or greater than a predetermined value is applied between the n-side electrode 27 and the p-side electrode 28, charges are injected into the active layer 23, and the active layer 23 begins to emit light. When the laser diode bar 10 is operated independently, when a current equal to or greater than a threshold current flows through the active layer 23, internal resonance occurs between the first end face coating layer 11 and the second end face coating layer 12, and laser light LB transmitted through the first end face coating layer 11 is emitted. E 1, when the laser diode bar 10 is assembled into a laser module 60 and operated, when a current equal to or greater than a threshold current flows through the active layer 23, external resonance occurs between the external cavity mirror 40 and the second end face coating layer 12, and the laser light LB E is emitted forward.

[0046] 4 and 5, an oxide film 13 is formed on the outermost surface of the first end face coating layer 11. The oxide film 13 is formed by absorbing the above-mentioned siloxane compound in the atmosphere surrounding the emitter 20 when the laser light LB E This is a deposition film that was decomposed by the gas and adhered to the front end surface.

[0047] That is, the oxide film 13 is a compound of silicon (Si) and oxygen (O). The oxide film 13 also contains several percent to several tens of percent of carbon. This is generated during the photodecomposition process of the siloxane compound, and is presumably taken into the oxide film 13 during its deposition. The oxide film 13 also contains phosphorus as an impurity. Laser light LB E It is presumed that when the phosphorus is emitted, the housing 50 or an adhesive such as solder used inside the housing 50 is heated, causing the phosphorus to diffuse into the atmosphere and be incorporated into the oxide film 13.

[0048] Note that the oxide film 13 may not contain phosphorus depending on the manufacturing process of the laser diode bar 10 or the laser module 60. In other words, it can be said that the oxide film 13 contains carbon or contains carbon and phosphorus.

[0049] On the other hand, the oxide film 13 does not contain argon. Silicon oxide films formed by sputtering often contain argon gas contained in the sputtering atmosphere, but the oxide film 13 is not formed by sputtering. Therefore, it is presumed that it does not contain argon as an impurity.

[0050] As shown in FIG. 4, the oxide film 13 is formed on the outermost surface of the first end face coating layer 11 by the laser beam LB. E The first portion 11a is formed in a region including the transparent portion (hereinafter, referred to as the first portion 11a).

[0051] 5, when viewed in a cross section intersecting the front end face and the rear end face, the thickness of the oxide film 13 is the thickest at the first portion 11a and becomes thinner along the front end face with increasing distance from the first portion 11a. Also, the hardness of the oxide film 13 is the lowest at the first portion 11a and becomes higher along the front end face with increasing distance from the first portion 11a.

[0052] The oxide film 13 can be formed during the process of adjusting the laser diode bar 10 or the laser module 60 before shipping. Usually, before shipping the laser diode bar 10 or the laser module 60, the following inspection is performed. First, the laser beam LB is continuously applied for a certain period of time at a power equal to or lower than the normal use conditions. E The laser beam LB is emitted. E Before and after the emission of the laser light LB E It is then determined whether the change in characteristics is within an allowable range. During this inspection process, an oxide film 13 is formed on the outermost surface of the first end face coating layer 11 due to decomposition of the siloxane compound. If the thickness of the oxide film 13 is thinner than the desired value, the laser light LB is further applied until the thickness reaches the desired value. E Alternatively, the laser light LB E The hardness of the oxide film 13 may be adjusted by increasing the power of the laser beam LB in these processes. E The power and temperature of the laser diode bar 10 are adjusted.

[0053] [Findings that led to this disclosure] As disclosed in Patent Documents 1 to 4, when the siloxane compound in the surrounding atmosphere is decomposed and an oxide film 13 is deposited on the outermost surface of the first end face coating layer 11, the laser light LB E This will adversely affect the characteristics of the emitter 20 and the operational reliability of the laser diode bar 10 during long-term use.

[0054] However, as a result of intensive research by the present inventors, when the laser diode bar 10 is assembled and operated in a laser module 60 as shown in FIG. 1, it has been found that, depending on the properties of the oxide film 13, external resonance is likely to occur between the external cavity mirror 40 and the second facet coating layer 12. It has also been found that the characteristic parameters of the oxide film 13 that affect the external resonance are the film thickness and hardness. Note that the hardness in this specification is obtained by the following procedure. First, a force curve on the surface of the first facet coating layer 11 including the oxide film 13 is obtained by atomic force microscopy (AFM). Next, fitting is performed on the obtained result using a contact mechanical model, and the obtained elastic modulus is taken as the hardness. Note that the contact mechanical model used for fitting is the DMT (Derjaguin-Muller-Toporov) model.

[0055] FIG. 6 shows the results of actually determining the relationship between the thickness and hardness of the oxide film 13 and the likelihood of external resonance occurring.

[0056] As shown in Fig. 6, according to the study by the inventors of the present application, the film thickness at which external resonance is likely to occur is 3 nm or more and 30 nm or less, and the hardness at which external resonance is likely to occur is 20 GPa or more and less than 60 GPa.

[0057] It was also found that the thickness of the oxide film 13 is more preferably 10 nm or more and 30 nm or less, and the hardness is more preferably 20 GPa or more and 40 GPa or less.

[0058] Note that 60 MPa corresponds to the hardness of the first end face coating layer 11 when the first end face coating layer 11 is a silicon oxide film of stoichiometric composition, i.e., SiO2, and no oxide film 13 is formed (comparative example).

[0059] The hardness of the oxide film 13 is lower than that of SiO2 because of its low density. In other words, it is presumed that the composition of the oxide film 13 is not stoichiometric (SiO2) and is deficient in oxygen. xIt is considered to be represented by (0 < x < 2).

[0060] In this way, in a state where there is oxygen deficiency, it is considered that a large number of unbonded hands exist in the oxide film 13. Further, the presence of unbonded hands increases the absorption coefficient of the oxide film 13. That is, the oxide film 13 E functions as an absorber of the laser beam LB.

[0061] When the oxide film 13 absorbs a part of the laser beam LB E the effective reflectance on the front end face of the emitter 20 decreases. As a result, in the external resonator formed between the second end face coat layer 12 of the laser diode bar 10 and the external resonance mirror 40, it is presumed that the gain due to the internal resonance of the emitter 20 increases and the occurrence of external resonance is suppressed from becoming difficult.

[0062] As described above, when the oxide film 13 absorbs a part of the laser beam LB E the oxide film and its surroundings generate heat, which may reduce the operating reliability of the laser diode bar 10 or cause destruction of the laser diode bar 10 or the emitter 20.

[0063] The inventors of the present application have found that by defining the film thickness and hardness range of the oxide film 13 as described above, it is possible to suppress the excessive increase in the amount of heat generation and suppress the occurrence of a decrease in the operating reliability of the laser diode bar 10 and the destruction of the laser diode bar 10 or the emitter 20.

[0064] [Effects, etc.] As described above, the laser diode bar (semiconductor laser element) 10 according to the present embodiment has a plurality of emitters 20 arranged at intervals along the Y direction which is the longitudinal direction.

[0065] The emitter 20 has a front end face which is an emission end face of the laser beam LB E and a rear end face facing the front end face, and from each of the front end faces of the plurality of emitters 20, the laser beam LB Eis emitted.

[0066] A first end face coating layer 11 is provided on the front end face of the emitter 20, and a second end face coating layer 12 is provided on the rear end face. E An oxide film 13 containing a compound of silicon and oxygen is formed on the first portion 11a through which the light passes. The hardness of the oxide film 13 is lower than that of SiO2.

[0067] The oxide film 13 has a thickness of 3 nm or more and 30 nm or less, and a hardness of 20 GPa or more and less than 60 GPa.

[0068] By configuring the laser diode bar 10 and the emitter 20 in this way, the oxide film 13 is irradiated with laser light LB E This allows the second end face coating layer 12 of the laser diode bar 10 to function as an absorber for the laser light LB, thereby reducing the effective reflectance at the front end face of the emitter 20. This makes it easier for external resonance to occur in the external cavity formed between the second end face coating layer 12 of the laser diode bar 10 and the external cavity mirror 40. E This prevents the amount of heat generated in the oxide film 13 and its surroundings due to absorption of the radiation from becoming too large, thereby preventing a decrease in the operational reliability of the laser diode bar 10 and damage to the laser diode bar 10 or the emitter 20.

[0069] When viewed in a cross section intersecting the front and rear end faces of the emitter 20, the thickness of the oxide film 13 is the thickest at the first portion 11a and becomes thinner along the front end face with increasing distance from the first portion 11a. In addition, the hardness of the oxide film 13 is the lowest at the first portion 11a and becomes higher along the front end face with increasing distance from the first portion 11a.

[0070] By thus defining the thickness distribution and hardness distribution of the oxide film 13, the laser beam LB E As the distance from the center of the front end face increases, the oxide film 13 approaches a stoichiometric composition and becomes thinner. EThe function of the oxide film 13 as an absorber of the laser light LB decreases with increasing distance from the first portion 11a along the front end face. As a result, the function of the oxide film 13 as an absorber of the laser light LB decreases with increasing distance from the first portion 11a along the front end face. E This can reduce the amount of absorption and unnecessary heat generation.

[0071] The thickness of the oxide film 13 is more preferably 10 nm or more and 30 nm or less, and the hardness of the oxide film 13 is more preferably 20 GPa or more and 40 GPa or less.

[0072] By specifying the thickness and hardness of the oxide film 13 in this way, it is possible to further reduce the effective reflectance at the front end face of the emitter 20, making it easier for external resonance to occur. In addition, it is possible to reduce the amount of heat generated in and around the oxide film 13, and it is possible to reliably prevent the deterioration of the operational reliability of the laser diode bar 10 and the occurrence of damage to the laser diode bar 10 or the emitter 20.

[0073] The oxide film 13 contains carbon or carbon and phosphorus. As described above, the carbon content is about several percent to several tens of percent. The oxide film 13 also contains about several percent of phosphorus, although this depends on the manufacturing conditions and the like.

[0074] Since the oxide film 13 contains a large amount of elements other than silicon and oxygen, the number of dangling bonds in the oxide film 13 increases, and the laser light LB E In other words, it is presumed that the above-mentioned function as an absorbent is improved.

[0075] It is also presumed that the phosphorus incorporated during the formation of the oxide film 13 accelerates the reaction for forming the oxide film 13, enabling the oxide film 13 with a desired thickness to be formed in a shorter time.

[0076] In addition, in this embodiment, the semiconductor laser element has been described by taking as an example a laser diode bar 10 having a plurality of emitters 20. In this laser diode bar 10, laser light LB is emitted from each of the front end faces of the plurality of emitters 20. E However, the configuration of the semiconductor laser element is not particularly limited to this. For example, the semiconductor laser element may be a laser diode having a single emitter 20.

[0077] As mentioned above, the laser light LB E The shorter the wavelength of the light, the more the photodecomposition of the siloxane compound proceeds, and the more easily the oxide film 13 grows.

[0078] From this point of view, the laser light LB E The wavelength range is preferably from ultraviolet to blue, that is, from 350 nm to 460 nm.

[0079] The laser module 60 according to this embodiment includes a plurality of laser diode bars 10 and a plurality of laser beams LB emitted from a plurality of emitters 20. E The laser module 60 includes at least a diffraction grating 30 for coupling the laser light LB E and a housing 50 that houses the laser diode bars 10, the diffraction grating 30, and the external cavity mirror 40.

[0080] The emitter 20 emits laser light LB E A second end face coating layer (reflective layer) 12 having a predetermined reflectance is provided on the rear end face of the optical fiber.

[0081] External cavity mirror 40 and laser light LB E An external resonator is formed between the emitter 20 and the second end face coating layer 12 from which the laser beam is emitted, and a combined laser beam (module laser beam LB M ) is emitted to the outside of the housing 50.

[0082] According to this embodiment, the laser light LB emitted from each of the multiple emitters 20 E Combined high power combined laser light (module laser light LB M ) can be obtained.

[0083] In addition, the oxide film 13 described above is formed on the outermost surface of the first end face coating layer 11 of each emitter 20. This makes it possible to reduce the reflectance at the front end face of the emitter 20, and laser oscillation is more likely to occur in the external cavity formed between the external cavity mirror 40 and the second end face coating layer 12 of the emitter 20. As a result, the module laser light LB M The output of the device can be increased.

[0084] In this embodiment, a plurality of laser beams LB E However, the present invention is not limited to this. E Alternatively, another optical element, for example a prism, may be used as the optical coupling element for coupling.

[0085] In addition, the laser module 60 may have one laser diode bar 10. In this case, the laser light LB emitted from each of the multiple emitters 20 is E Combined high power combined laser light (module laser light LB M In addition, a plurality of laser diodes each having a single emitter 20 may be arranged inside the housing 50, and the laser light LB emitted from each of the plurality of emitters 20 may be E Combine the module laser light LB M may be obtained.

[0086] (Embodiment 2) A laser oscillator may be configured using one or more laser modules 60 according to the first embodiment. When a plurality of laser modules 60 are used, the module laser light LB emitted from each laser module 60 MThe laser beams are further combined into one processing laser beam. For example, a spatial combining technique or a polarization combining technique is used as the combining technique. Also, a laser processing device may be configured by incorporating this laser oscillator.

[0087] FIG. 7 is a schematic diagram showing the configuration of a laser processing apparatus according to the second embodiment.

[0088] The laser processing apparatus 200 includes a housing 90, a laser oscillator 120, an optical fiber 130, and a laser head 140. Except for the control unit 100 and the power source 110, the laser oscillator 120 is housed inside the housing 90. In addition, a portion of the optical fiber 130 is also housed inside the housing 90.

[0089] The laser oscillator 120 has a plurality of laser modules 60, a beam combiner 70, a focusing optical unit 80, a control unit 100, and a power supply 110. The configuration of the laser module 60 is the same as that described in the first embodiment, and therefore a description thereof will be omitted.

[0090] The beam combiner 70 has a plurality of optical components (not shown) and combines the module laser light LB emitted from each of the plurality of laser modules 60. M into one processing laser beam LB1. In this case, both the spatial combining technique and the polarization combining technique are used. However, depending on the number of laser modules 60, only one of the spatial combining technique and the polarization combining technique may be used.

[0091] The focusing optical unit 80 has at least a focusing lens (not shown), receives the processing laser light LB1 emitted from the beam combiner 70, and focuses the light toward the incident end of the optical fiber .

[0092] The optical fiber 130 has at least a core and a cladding, not shown. The core is provided at the axial center of the optical fiber 130, and functions as an optical waveguide that guides the processing laser light LB1 incident from the focusing optical unit 80 to the laser head 140. The cladding is provided so as to surround the outer periphery of the core, and functions as an optical confinement layer that confines the processing laser light LB1 inside the core.

[0093] The control unit 100 controls the laser oscillation of the laser oscillator 120. Specifically, the control unit 100 controls the laser oscillation of each laser module 60 by supplying control signals such as output voltage and on-time to the power supply 110. It is also possible to control the laser oscillation of each laser module 60 individually. For example, the laser oscillation output and on-time may be different for each laser module 60. The control unit 100 may also control the operation of a robot (not shown) to which the laser head 140 is attached.

[0094] The control unit 100 is composed of, for example, one or more CPUs (Central Processing Units) and a storage unit (not shown) composed of semiconductor memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The storage unit may be composed of an HDD (Hard Disk Drive), SSD (Solid State Drive), etc.

[0095] For example, processing parameters during laser processing are simultaneously displayed on the display unit 101. The display unit 101 usually includes a display device such as a liquid crystal display or an organic EL display.

[0096] As described above, the power source 110 supplies power for performing laser oscillation to each of the multiple laser modules 60. The power supplied to each laser module 60 may be different in response to a command from the control unit 100. The power source 110 may also supply power to a moving part of the laser processing apparatus 200, for example, the robot described above. Note that power may be supplied to the moving part of the laser processing apparatus 200 from a separate power source (not shown).

[0097] By configuring the laser oscillator 120 in this way, it is possible to obtain a high-output laser processing apparatus 200 in which the output of the processing laser light LB1 exceeds several kW.

[0098] The laser head 140 irradiates the processing laser light LB1 transmitted through the optical fiber 130 toward the outside. For example, in the laser processing apparatus 200 shown in Fig. 7, the processing laser light LB1 is irradiated toward a workpiece W, which is an object to be processed and arranged at a predetermined position. In this manner, the workpiece W is laser processed.

[0099] In this embodiment, four laser modules 60 are mounted on the laser oscillator 120, but this is not particularly limited. The number of mounted laser modules 60 can be changed as appropriate depending on the output specifications required for the laser processing device 200 and the output specifications of each laser module 60. For example, there may be only one laser module 60. In this case, the module laser light LB M The beam combiner 70 is omitted. Therefore, the module laser beam LB emitted from the laser module 60 becomes the processing laser beam LB1. M That is, the processing laser light LB1 is incident on the focusing optical unit 80.

[0100] As described above, the laser oscillator 120 according to this embodiment includes one or more laser modules 60, a beam combiner 70, a focusing optical unit 80, a control unit 100, and a power supply 110.

[0101] The laser module 60 emits a laser beam LB M When the laser oscillator 120 has a plurality of laser modules 60, the beam combiner 70 outputs laser light LB M are combined into one processing laser beam LB1.

[0102] The focusing optical unit 80 focuses the processing laser light LB1 emitted from the beam combiner 70 and emits it to the outside of the laser oscillator 120. In this embodiment, the focusing optical unit 80 focuses the processing laser light LB1 and emits it to the incident end of the optical fiber 130.

[0103] The control unit 100 controls the laser oscillation of the laser oscillator 120. The power supply 110 supplies the laser module 60 with power for performing laser oscillation.

[0104] According to the laser oscillator 120 of this embodiment, laser oscillation is likely to occur in the external cavity formed between the external cavity mirror 40 and the second end face coating layer 12 of the emitter 20. As a result, the module laser light LB M This allows the output of multiple module laser beams LB M The output of the processing laser beam LB1 combined into one can be made high, for example, several kW.

[0105] Moreover, the laser processing apparatus 200 according to this embodiment includes at least a laser oscillator 120, an optical fiber 130, and a laser head 140.

[0106] The laser oscillator 120 emits a processing laser beam LB1. The optical fiber 130 receives the processing laser beam LB1 emitted from the laser oscillator 120 and guides it to the laser head 140. The laser head 140 is attached to the emission end of the optical fiber 130, receives the processing laser beam LB1 guided by the optical fiber 130, and irradiates the workpiece W with the processing laser beam LB1.

[0107] According to the laser processing apparatus 200 of the present embodiment, the workpiece W can be laser processed using a high-power processing laser light LB1. This allows, for example, drilling or cutting a thick plate of the workpiece W in a short time. In addition, by using the optical fiber 130, it becomes easy to guide the processing laser light LB1 to the workpiece W. In addition, by providing the laser head 140 at the tip of the optical fiber 130, it becomes easy to irradiate the processing laser light LB1 to a desired position of the workpiece W. [Industrial Applicability]

[0108] The semiconductor laser element of the present disclosure is useful because it facilitates external resonance and can provide high-output laser light. [Explanation of symbols]

[0109] 10 Laser diode bar (semiconductor laser element) 11 First end face coating layer 11a Part 1 12 Second end face coating layer 13. Oxide Film 20 Emitter 21 n-type substrate 22 n-type cladding layer 23 Active layer 24 p-type cladding layer 25 p-type contact layer 26 Insulating layer 27 n-side electrode 28 p side electrode 30 Diffraction grating (optical coupling element) 40 External cavity mirror 50 Case 60 Laser Module 70 Beam combiner 80 Condenser optical unit 90 Case 100 Control section 101 Display section 110 Power supply 120 Laser Oscillator 130 Optical Fiber 140 Laser Head 200 Laser processing equipment LB M Module laser light (combined laser light) LB1 laser beam for processing Double work

Claims

1. A semiconductor laser element having an emitter that emits laser light, the emitter has a front end face which is an output end face of the laser light, and a rear end face opposite to the front end face, a first end surface coating layer is provided on the front end surface, and a second end surface coating layer is provided on the rear end surface, an oxide film including a compound of silicon and oxygen is formed on a first portion of the outermost surface of the first end face coating layer through which the laser light passes; The hardness of the oxide film is SiO ２ A semiconductor laser element having a hardness lower than that of the semiconductor laser element.

2. 2. The semiconductor laser device according to claim 1, The hardness of the oxide film is 20 GPa or more and less than 60 GPa.

3. 2. The semiconductor laser device according to claim 1, The thickness of the oxide film is 3 nm or more and 30 nm or less.

4. 2. The semiconductor laser device according to claim 1, When viewed in a cross section intersecting the front end surface and the rear end surface, the thickness of the oxide film is greatest at the first portion and decreases with increasing distance from the first portion along the front end surface; a hardness of the oxide film is lowest at the first portion and increases with increasing distance from the first portion along the front end face, the hardness being such that the hardness of the oxide film increases with increasing distance from the first portion along the front end face.

5. 2. The semiconductor laser device according to claim 1, 13. A semiconductor laser device, wherein the oxide film does not contain argon but contains carbon or contains carbon and phosphorus.

6. 2. The semiconductor laser device according to claim 1, The hardness of the oxide film is 20 GPa or more and 40 GPa or less.

7. 2. The semiconductor laser device according to claim 1, The thickness of the oxide film is 10 nm or more and 30 nm or less.

8. 2. The semiconductor laser device according to claim 1, The wavelength region of the laser light is 350 nm or more and 460 nm or less.

9. 9. The semiconductor laser device according to claim 1, the semiconductor laser element is a laser diode bar having a plurality of the emitters spaced apart from one another along a longitudinal direction; a semiconductor laser element, wherein the laser light is emitted from each of the front end faces of the plurality of emitters.

10. The semiconductor laser element according to claim 9 ; an optical coupling element that couples the plurality of laser beams emitted from the plurality of emitters; an external cavity mirror that reflects the laser light coupled by the optical coupling element toward the optical coupling element; a housing that houses one or more of the semiconductor laser elements, the optical coupling element, and the external cavity mirror; an external cavity is configured between the external cavity mirror and the second end face coating layer formed on the emitter, A laser module, characterized in that a combined laser beam combined by the optical coupling element is emitted to the outside of the housing.

11. A laser module according to claim 10; A control unit; A laser oscillator including at least a power source, The laser module is one or more. The control unit controls laser oscillation of the laser oscillator, The laser oscillator is characterized in that the power source supplies power for performing the laser oscillation to the laser module.

12. 12. The laser oscillator according to claim 11, Further comprising a focusing optical unit; The light collecting optical unit includes: When the number of the laser modules mounted on the laser oscillator is one, the combined laser beam is condensed and output to the outside of the laser oscillator; A laser oscillator characterized in that, when the number of the laser modules mounted on the laser oscillator is multiple, the processing laser light generated by combining the multiple combined laser light is focused and emitted to the outside of the laser oscillator.

13. A laser beam splitter comprising at least the laser oscillator according to claim 11, an optical fiber, and a laser head, the optical fiber receives the processing laser light emitted from the laser oscillator and guides the light to the laser head; The laser head is attached to the output end of the optical fiber, receives the processing laser light guided by the optical fiber, and irradiates the processing laser light toward a workpiece.

14. A laser beam splitter comprising: a laser oscillator according to claim 11; an optical fiber; and a laser head; the optical fiber receives the processing laser light emitted from the laser oscillator and guides the light to the laser head; the laser head is attached to an output end of the optical fiber, receives the processing laser light guided by the optical fiber, and irradiates the processing laser light toward a workpiece; When one laser module is mounted on the laser oscillator, the processing laser beam is the combined laser beam, A laser processing apparatus characterized in that, when a plurality of the laser modules are mounted on the laser oscillator, a plurality of the combined laser beams emitted respectively from the plurality of the laser modules are combined to generate the processing laser beam.

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