External resonance type laser oscillator and processing apparatus

Abstract

To provide a semiconductor laser element capable of achieving a high output of laser processing equipment.SOLUTION: The semiconductor laser element is placed in a piece of wavelength beam-combining type processing equipment that has an external resonant mirror. The semiconductor laser element includes: a resonator structure having a light-emitting layer that emits laser light; a first reflective film and a second reflective film that are formed on a non-output end face and an output end face respectively of the resonator structure for reflecting the laser light. In a case of defining the reflectance of the second reflective film as R1 when the resonator structure oscillates the laser light at power 1.4 times the minimum threshold power, which is the minimum power at which the resonator structure oscillates the laser light, the reflectance of an external resonant mirror as R(Oc), and the coupling efficiency which is the rate at which reflected light from the external resonator mirror enters the resonator structure as C, the reflectance R of the second reflective film at the gain wavelength of the semiconductor laser element satisfies the relational expression R1≤R≤R(Oc)×C.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to External resonance type laser oscillator and a processing apparatus.

Background Art

[0002] In recent years, laser processing of various materials such as copper, gold, and resin has been expected. For example, in the automotive industry, electrification, miniaturization, high rigidity, improved design freedom, and improved productivity are required, and there is high expectation for laser processing.

[0003] In particular, in the manufacture of motors and batteries for electric vehicles, when performing metal processing such as copper using laser light, it is necessary to use a laser light source that can output blue-violet to blue (wavelength 350 nm or more and 450 nm or less) laser light with high light absorption efficiency. In addition, in order to realize highly productive laser processing, a laser light source having a high output and a high beam quality with high condensing property is required.

[0004] For this reason, there is a demand for the development of a laser processing apparatus that outputs laser light with a high output and a high beam quality by condensing a plurality of laser lights. For example, Patent Document 1 discloses a wavelength beam combining (WBC) system that condenses laser light output from a plurality of beam emitters arranged one-dimensionally. In a WBC type laser processing apparatus, for example, a monolithic type semiconductor laser array is used.

[0005] A monolithic type semiconductor laser array has a plurality of emitter portions that output laser light. Therefore, the optical output value of a WBC type processing apparatus corresponds to the sum of the output values of the laser light output from the plurality of emitter portions.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] In a semiconductor laser array included in a conventional WBC type processing apparatus, a reflection film is provided on its emission end face. Depending on the value of the reflectance (hereinafter, the "reflectance at the gain wavelength" may also be simply referred to as "reflectance") at the gain wavelength of the semiconductor laser array having this reflection film, there is a possibility that a sufficient output value cannot be obtained from the processing apparatus.

[0008] This disclosure aims to increase the output power of a laser processing apparatus External resonance type laser oscillator and to provide a processing apparatus. MEANS FOR SOLVING THE PROBLEMS

[0009] This disclosure External resonance type laser oscillator is A semiconductor laser element, An external resonance mirror, and comprises The semiconductor laser element is a resonator structure having a light emitting layer that emits laser light, a first reflection film and a second reflection film provided on the non-emission end face and the emission end face of the resonator structure, respectively, for reflecting the laser light, and The external resonance mirror causes external resonance with the first reflective film, when the reflectance of the second reflection film when the resonator structure laser oscillates at a power that is 1.4 times the minimum value of the threshold power, which is the minimum power at which the resonator structure laser oscillates, is R1, the reflectance of the external resonator mirror is R(Oc), and the coupling efficiency, which is the ratio at which the reflected light from the external resonator mirror enters the resonator structure, is C, the reflectance R of the second reflection film at the gain wavelength of the semiconductor laser element satisfies R1 ≦ R ≦ R(Oc) × C the relational expression represented by.

[0010] The present disclosure External resonance type laser oscillator is A semiconductor laser element, An external resonance mirror, and comprises The semiconductor laser element is a resonator structure having a light-emitting layer that emits laser light, a first reflective film and a second reflective film respectively provided on a non-emitting end face and an emitting end face of the resonator structure, for reflecting the laser light, and The external resonance mirror causes external resonance with the first reflective film, when the resonator structure laser oscillates at a power that is 1.4 times the minimum value of the threshold power, which is the minimum power at which the resonator structure laser oscillates, let the reflectivity of the second reflective film be R1, the reflectivity of the external resonant mirror be R(Oc), and the coupling efficiency, which is the ratio of the reflected light from the external resonant mirror incident on the resonator structure, be C. Then, the reflectivity R of the second reflective film at the gain wavelength of the semiconductor laser element is R1 ≦ R ≦ 2 × R(Oc) × C satisfies the relational expression represented by External resonance type laser oscillator .

[0011] The present disclosure External resonance type laser oscillator is An external resonance mirror, A semiconductor laser element, a resonator structure having a light-emitting layer that emits laser light, a first reflective film and a second reflective film respectively provided on a non-emitting end face and an emitting end face of the resonator structure, for reflecting the laser light, and and a semiconductor laser element comprising , when the resonator structure laser oscillates at a power that is 1.4 times the minimum value of the threshold power, which is the minimum power at which the resonator structure laser oscillates, let the reflectivity of the second reflective film be R1, the reflectivity of the external resonant mirror be R(Oc), and the coupling efficiency, which is the ratio of the reflected light from the external resonant mirror incident on the resonator structure, be C. Then, the reflectivity R of the second reflective film at the gain wavelength of the semiconductor laser element is R1 ≤ R ≤ 3 × R(Oc) × C satisfies the relational expression shown by

[0012] According to the present disclosure External resonance type laser oscillator is Comprises a semiconductor laser array having a plurality of the semiconductor laser elements.

[0013] According to the present disclosure The wavelength beam combining type processing apparatus Comprises the external resonance type laser oscillator according to any one of the above.

[0014] According to the present disclosure The wavelength beam combining type processing apparatus Comprises the above-described external resonance type laser oscillator.

Advantages of the Invention

[0015] According to the present disclosure, it is possible to provide a semiconductor laser element, a semiconductor laser array, and a processing apparatus capable of increasing the output power of a laser processing apparatus.

Brief Description of the Drawings

[0016]

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DETAILED DESCRIPTION OF THE INVENTION

[0017] First, with reference to FIGS. 1 to 3, the background leading to the semiconductor laser element, semiconductor laser array, and processing apparatus according to the present disclosure will be described.

[0018] FIG. 1 is a conceptual diagram of a high-power laser oscillator (hereinafter simply referred to as "laser oscillator") 10 used in a WBC type processing apparatus according to the present embodiment. FIG. 2 is a diagram showing a semiconductor laser array 200 according to the present embodiment. FIG. 3 is a diagram showing the relationship between the semiconductor laser array 200 and the diffraction grating 208 according to the present embodiment.

[0019] The laser oscillator 10 includes a plurality of semiconductor laser arrays 201 to 205, a plurality of beam twister units 206, a diffraction grating 208, and an external resonant mirror 210. In the following description, when not distinguishing the plurality of semiconductor laser arrays 201 to 205 provided in the laser oscillator 10, they will be described collectively as the semiconductor laser array 200.

[0020] The semiconductor laser array 200 has a resonator structure 214. The resonator structure 214 is an active layer in which a first semiconductor layer 216, a light-emitting layer 215, and a second semiconductor layer 217 are stacked. Further, the semiconductor laser array 200 has a ridge stripe structure, and a plurality of emitter portions 234 for emitting laser light 1 are formed in a stripe shape in the resonator structure 214. In the resonator structure 214, the portion directly below the convex portion 233 forms individual emitter portions 234.

[0021] In the resonator structure 214, laser light 1 is emitted from one end face of the emitter portion 234. Hereinafter, the end face from which the laser light 1 of the semiconductor laser array 200 is emitted will be referred to as the "emission end face", and the end face located on the side opposite to the emission end face and from which the laser light 1 is not emitted will be referred to as the non-emission end face.

[0022] A reflection film 221 is provided on the emission end face of the semiconductor laser array 200, and a reflection film 222 is provided on the non-emission end face.

[0023] The plurality of beam twister units 206 are respectively arranged on the emission end face side of the semiconductor laser arrays 201 to 205. The beam twister unit 206 rotates each of the plurality of laser lights 1 emitted from the semiconductor laser arrays 201 to 205 by 90°. This prevents the plurality of laser lights 1 having wavelengths close to each other from interfering with each other. The laser light 1 rotated by the beam twister unit 206 is incident on the diffraction grating 208.

[0024] The diffraction grating 208 is a transmission or reflection diffraction grating. In FIG. 1, it is shown that the diffraction grating 208 is a transmission diffraction grating. Thus, when the diffraction grating 208 is a transmission diffraction grating, the diffraction grating 208 diffracts the incident laser beam 1 at an emission angle (diffraction angle) β according to the wavelength of the laser beam 1 and emits it as the external resonance light 2. The external resonance light 2 emitted from the diffraction grating 208 enters the external resonance mirror 210.

[0025] The external resonance mirror 210 is a partially transmissive mirror. A part of the light 4 of the external resonance light 2 is perpendicularly reflected toward the diffraction grating 208 by the external resonance mirror 210. Thereby, a laser beam having a predetermined lock wavelength causes external resonance between the reflection film 222 on the non-emission end face and the external resonance mirror 210 and is output as the laser beam 3 from the external resonance mirror 210. Here, the lock wavelength is uniquely determined by the positional relationship among the emitter section 234, the diffraction grating 208, and the external resonance mirror 210.

[0026] (Lock wavelength) The lock wavelengths of the semiconductor laser arrays 201 to 205 will be described.

[0027] Among the laser beams 1 emitted from the respective emitter sections 234 of the semiconductor laser arrays 201 to 205, only the light 4 that satisfies the diffraction condition of the diffraction grating 208 and is perpendicularly reflected by the external resonance mirror 210 returns to the emitter section 234 of the emission source and undergoes external resonance by the reflection film 222 on the non-emission end face and the external resonance mirror 210. Then, laser oscillation due to external resonance occurs.

[0028] In the semiconductor laser array 200, assuming that the lock wavelength of each emitter section 234 corresponding to the current injection region is λL, the period of the diffraction grating 208 is d, the incident angle of the laser beam 1 with respect to the diffraction grating 208 is α, the emission angle of the external resonance light 2 is β, and the order is m (an integer), the lock wavelength λL is calculated based on the relational expression (0).

[0029] d(sinα + sinβ)=mλL (0)

[0030] Note that the order m can take different values depending on the arrangement position of the diffraction grating 208. For example, if the diffraction grating 208 is arranged such that m = 1, the calculation becomes simple.

[0031] For example, as shown in FIG. 1, assume that five semiconductor laser arrays 201 to 205 are arranged in the laser oscillator 10 such that the incident angles α of the laser light 1 with respect to the diffraction grating 208 are 21.6 deg, 22.4 deg, 23.2 deg, 24.0 deg, and 24.8 deg, respectively.

[0032] In this case, the locking wavelengths λL_CENTER of the emitter portions 234 located at the centers of the semiconductor laser arrays 201 to 205 are 435.9 nm, 440.3 nm, 444.5 nm, 448.8 nm, and 453.0 nm, respectively, as shown in Table 1. That is, the locking wavelengths λL_CENTER of the semiconductor laser arrays 201 to 205 change by approximately 4.3 nm each.

[0033] [Table 1]

[0034] Next, the case where the locking wavelength λL of the semiconductor laser array 200 satisfies the following element conditions (A) to (B) and installation conditions (C) to (E) will be described as an example.

[0035] <Element Conditions> (A) The semiconductor laser array 200 has 25 emitter portions 234. (B) The length (hereinafter referred to as the "array width") W in the direction in which the emitter portions 234 are arranged in the semiconductor laser array 200 is 10 mm.

[0036] <Installation Conditions> (C) The laser light 1 emitted from the semiconductor laser array 200 has a wavelength of about 400 nm or more and 500 nm or less, and the incident angle α with respect to the diffraction grating 208 is 21.1°. (D) The distance L from the semiconductor laser array 200 to the diffraction grating 208 is 2.6 m. (E) The diffraction grating 208 has a groove period of 3000 lines / mm, that is, the period d of the diffraction grating 208 is 0.333 μm.

[0037] When the above element conditions (A), (B) and installation conditions (C) to (E) are satisfied, the locking wavelength λL in each emitter section 234 of the semiconductor laser array 200 is as shown in Table 2.

[0038]

Table 2

[0039] The numbers of the emitter sections 234 in Table 2 are the numbers assigned to each of the 25 emitter sections 234. Specifically, in FIG. 3, among the plurality of emitter sections 234, numbers 1 to 25 are sequentially assigned from the emitter section located on one end side (right end side) to the emitter section located on the other end side (left end side).

[0040] As shown in Table 2, the locking wavelength λL of the first emitter section 234 from one end side (right end side) is 435.7 nm, and the locking wavelength λL of the 25th emitter section 234 is 436.51 nm. As it progresses to the other end side (left end side), the locking wavelength λL increases by about 0.05 nm each time, and the difference ΔλL_BAR in the locking wavelengths λL of the emitter sections 234 at both ends of the semiconductor laser array 200 is about 1.1 nm.

[0041] The respective emitter portions 234 of the semiconductor laser arrays 201 to 205 have different relative positions with respect to the diffraction grating 208. For this reason, external resonance occurs at different wavelengths in the emitter portion 234, and the laser light 1 oscillates. However, the laser light 1 from a large number of emitter portions 234 is condensed by the diffraction grating 208 and condensed onto one point on the incident surface of the external resonance mirror 210 as the external resonance light 2. Note that the higher the coincidence between the lock wavelength and the gain wavelength of the semiconductor laser arrays 201 to 205, the higher the output value of the laser light 3 (the output value of the laser oscillator 10). As a result, the output value of the processing apparatus including the laser oscillator 10 becomes higher.

[0042] Since the laser oscillator 10 condenses the laser light 1 emitted from the respective emitter portions 234, the laser light 3 becomes a high-output laser light. The output value of the laser light 3 corresponds to the sum of the output values of the laser light 1 emitted from the respective emitter portions 234.

[0043] Hereinafter, the reflectance of the reflection film 221 on the emission end face of the semiconductor laser array 200 will be described.

[0044] (When the reflectance of the reflection film 221 is high) When the reflectance of the reflection film 221 on the emission end faces of the semiconductor laser arrays 201 to 205 is made greater than 0%, theoretically, internal resonance occurs between the reflection film 221 on the emission end face and the reflection film 222 on the non-emission end face.

[0045] When the influence of the above-described internal resonance is greater than the influence of the external resonance between the reflection film 222 on the non-emission end face and the external resonance mirror 210 when the laser light 3 oscillates, the internal resonance may prevent the laser oscillation by the external resonance, and the output value of the laser light 3 may decrease.

[0046] For this reason, it is desirable to reduce the influence of the internal resonance, and it has been considered desirable to set the reflectance of the reflection film 221 on the emission end face to 0%, that is, for the laser light 1 emitted from the emitter portion 234 to transmit through the emission end face at 100%.

[0047] (When the reflectance of the reflection film 221 is low) The inventors noticed that it is not always desirable that the reflectance of the reflection film 221 on the emission end face is lower.

[0048] Before the semiconductor laser array 200 is incorporated into the laser oscillator 10, the gain wavelength and various characteristics of the semiconductor laser array 200 are measured.

[0049] When manufacturing the laser oscillator 10, in order to increase the output value of the laser light 3, it is necessary to maximize the consistency between the gain wavelength and the lock wavelength of the semiconductor laser array 200.

[0050] The gain wavelength is determined by the characteristics of the semiconductor laser array 200, and the lock wavelength is determined by the positional relationship between the semiconductor laser array 200 (especially the emitter section 234), the diffraction grating 208, and the external resonant mirror 210, as described above.

[0051] Therefore, in order to match the gain wavelength and the lock wavelength, it is necessary to measure the gain wavelength of the semiconductor laser array 200 in advance and adjust the positional relationship between the semiconductor laser array 200 (especially the emitter section 234), the diffraction grating 208, and the external resonant mirror 210 according to the measurement results.

[0052] In addition, the measurement of various characteristics is performed to select a semiconductor laser array suitable for incorporation into the laser oscillator 10.

[0053] The gain wavelength and various characteristics are measured based on the laser light 1 output when internal resonance occurs in the semiconductor laser array 200.

[0054] If the reflectance of the reflection film 221 on the emission end face is set to, for example, 0.005% (corresponding to the measurement limit value of a general reflectance measurement instrument), the amount of laser light 1 confined in the optical waveguide section of the emitter section 234 is very small, and internal resonance is unlikely to occur.

[0055] That is, the smaller the reflectivity of the reflection film 221 on the emission end face, the greater the power (hereinafter referred to as "threshold power") required to cause the semiconductor laser array 200 to oscillate by internal resonance.

[0056] While the laser oscillation is not occurring, the energy of the power (current) supplied to the semiconductor laser array 200 is not converted into light energy but into heat energy. When the heat energy is large, defects (for example, crystal defects) may occur inside the semiconductor laser array 200, and there is a risk that the light-emitting layer 215 and the emitter portion 234 will be damaged.

[0057] In particular, when crystal defects have occurred and damaged the portion corresponding to the light-emitting layer 215 of the emitter portion 234, the output value of the laser light 1 emitted from the emitter portion 234 decreases. As a result, the output value of the semiconductor laser array 200, and further the output value of the laser oscillator 10 based on external resonance, also decreases. As a result, the output value of the processing apparatus equipped with the laser oscillator 10 also decreases.

[0058] It is difficult to detect abnormal locations such as crystal defects and damaged portions in advance through measurement and analysis. Also, after the semiconductor laser array 200 is incorporated into the laser oscillator 10, an abnormal region may grow starting from the abnormal location inside the semiconductor laser array 200, and the laser output value of the laser oscillator 10 may further decrease. That is, there is a risk that the output value of the laser oscillator 10 will become unstable. As a result, there is a risk of causing a decrease and destabilization of the output value of the processing apparatus equipped with the laser oscillator 10.

[0059] In summary, when using a processing apparatus equipped with the laser oscillator 10 for processing a workpiece, the internal resonance generated in the semiconductor laser array 200 contributes to a decrease in the laser output value of the laser oscillator 10. On the other hand, in order to increase the laser output value of the laser oscillator 10, it is necessary to generate laser oscillation due to internal resonance and measure the gain wavelength and various characteristics before incorporating the semiconductor laser array 200 into the laser oscillator 10. Hereinafter, such measurement may also be referred to as "pre-measurement".

[0060] Note that the above problem also holds true for not only the semiconductor laser array 200 but also the semiconductor laser element 100 (see FIG. 7) having only one emitter section 234.

[0061] As a result of intensive studies on the internal resonance of the semiconductor laser array 200, the inventor has found that by adjusting the reflectivity of the reflection film 221 on the emission end face side of the semiconductor laser array 200 to an appropriate value, the following (Effect 1) and (Effect 2) can be obtained. (Effect 1) It is possible to perform pre-measurement with internal resonance while reducing the possibility of crystal defects occurring inside the semiconductor laser array 200. As a result, it is possible to suppress a decrease in the laser output value due to external resonance of the laser oscillator 10. (Effect 2) It is possible to reduce the influence of internal resonance when laser output is emitted from the laser oscillator 10 due to external resonance, and suppress a decrease in the laser output value of the laser oscillator 10.

[0062] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the numerical values, shapes, materials, components, the arrangement positions of the components, the connection forms, the processes (steps), and the order of the processes described below are merely examples and do not limit the present disclosure. Therefore, among the components in the following embodiments, the components not described in the independent claims indicating the highest concept of the present disclosure are described as arbitrary components.

[0063] In addition, each figure is a schematic diagram and is not drawn precisely. Therefore, scales and the like in each figure do not necessarily match. In each figure, substantially the same configurations are denoted by the same reference numerals, and overlapping descriptions are omitted or simplified.

[0064] [Embodiment] (Configuration of Semiconductor Laser Array) With reference to FIGS. 2, 4A, 4B, 5, and 6, the semiconductor laser array 200 according to this embodiment will be described in detail. FIGS. 4A and 4B are examples of profiles showing the wavelength dependence of the reflectance of the reflection film 221 on the emission end face, and show cases satisfying different film thickness conditions. FIG. 5 is an example of a profile showing the wavelength dependence of the reflectance of the reflection film 222 on the non-emission end face when a specific film thickness condition is satisfied. FIG. 6 is a graph showing the relationship between the threshold power and the reflectance of the reflection film 221 on the emission end face.

[0065] The semiconductor laser array 200 according to this embodiment will be described as a GaN-based semiconductor laser array that emits laser light 1 in a wavelength band of 405 nm or more and 450 nm or less.

[0066] The semiconductor laser array 200 includes a substrate 212 and a resonator structure 214. The semiconductor laser array 200 is a monolithic semiconductor laser array in which a plurality of emitter portions 234 are formed on a single substrate 212. Also, as described above, a reflection film 221 and a reflection film 222 are provided on the emission end face and the non-emission end face of the semiconductor laser array 200. Further, an n-side electrode 219 is formed on the back surface of the substrate 212, and a p-side electrode 283 is formed on the surface of the resonator structure 214.

[0067] In this embodiment, the substrate 212 is a single crystal substrate formed of single crystal gallium nitride (GaN), for example, an n-type hexagonal GaN substrate.

[0068] The first semiconductor layer 216 of the resonator structure 214 is a first cladding layer formed of an n-type semiconductor such as AlGaN, for example.

[0069] The light-emitting layer 215 is a layer that emits the laser light 1, and has a structure in which multiple quantum well layers are sandwiched by guide layers. The multiple quantum well layers are formed of, for example, undoped InGaN. The guide layers are formed of, for example, undoped GaN.

[0070] The composition ratio of the light-emitting layer 215 of the resonator structure 214 is adjusted according to the gain wavelength. When the laser oscillator 10 included in the processing apparatus according to the present embodiment has five semiconductor laser arrays 201 to 205 as described above, for example, as shown in Table 1 above, it has a width such that the lock wavelength is 435.9 nm or more and 453.0 nm or less. Therefore, it is necessary to match the gain wavelength to the lock wavelength.

[0071] The gain wavelength can be adjusted by adjusting the composition ratio of the light-emitting layer 215. Specifically, the gain wavelength can be adjusted by adjusting the In composition ratio of the multiple quantum well layers made of InGaN in the light-emitting layer 215. For example, when the In composition ratio is set to 17%, the gain wavelength of the semiconductor laser array 200 is on average 450 nm. Note that the temperature distribution when forming the light-emitting layer 215 may be adjusted to adjust the In composition for each emitter unit 234, and a semiconductor laser array having different gain wavelengths may be formed.

[0072] The second semiconductor layer 217 of the resonator structure 214 is configured by laminating, in order from the light-emitting layer 215 side, an electron overflow suppression layer, a second cladding layer, and a contact layer. The electron overflow suppression layer and the cladding layer are formed of a p-type semiconductor such as AlGaN, for example, and the contact layer is formed of a p-type semiconductor such as GaN, for example. A p-side electrode 283 is disposed on the contact layer.

[0073] Next, the emitter unit 234 will be described. In the second semiconductor layer 217, a plurality of convex portions 233 are formed in a stripe shape. Below the convex portions 233, an optical waveguide portion for confining light is formed due to the refractive index difference between the light-emitting layer 215 and the first semiconductor layer 216, and the refractive index difference between the light-emitting layer 215 and the second semiconductor layer 217.

[0074] The length x of the convex portion 233 is called the resonator length of the semiconductor laser array 200. The semiconductor laser array 200 of the present embodiment will be described assuming that the resonator length x is 2000 μm, the array width W is 9000 μm, and 40 emitter portions 234 each having a width of 225 μm are formed. The width of the convex portion 233 is, for example, 10 μm or more and 40 μm or less, and specifically, it is 15 μm.

[0075] The p-side electrode 283 is formed on the upper surface of the convex portion 233, more specifically, on the upper surface of the contact layer, and is connected to the upper surface of the optical waveguide portion through the contact layer. The p-side electrode 283 is an electrode that makes an ohmic contact with the contact layer above each optical waveguide portion. The p-side electrode 283 is formed of a metal material such as Pd, Pt, or Ni, for example. The p-side electrode 283 of the present embodiment has a two-layer structure composed of a Pd layer and a Pt layer.

[0076] The surface of the resonator structure 214 excluding the upper surface of the p-side electrode 283 is covered with an insulating film. Specifically, the insulating film covers the region of the upper surface of the contact layer where the p-side electrode 283 is not formed. The insulating film is made of, for example, SiO2 as a material.

[0077] Further, the semiconductor laser array 200 has a pad electrode (not shown) that covers the entire surface of the resonator structure 214, and a plurality of p-side electrodes 283 are connected to each other by this pad electrode.

[0078] The n-side electrode 219 is formed so as to cover the entire surface of the substrate 212.

[0079] The reflective film 221 on the emission end face of the semiconductor laser array 200 has its reflectivity set within a predetermined range. The predetermined range will be described later. Also, as will be described later, since the reflectivity of the reflective film 221 is not 0, the reflective film 221 slightly reflects the laser light 1.

[0080] The reflective film 221 is a dielectric multilayer film formed by a combination of a silicon dioxide (SiO2) layer and an aluminum oxide (Al2O3) layer. By adjusting the thickness of each layer and the refractive index of each layer, the reflectivity of the reflective film 221 can be changed. Note that the reflectivity of the reflective film 221 with respect to the laser light 1 depends on the wavelength of the laser light 1.

[0081] For example, if the gain wavelength of the semiconductor laser array 200 is 450 nm and it is desired to obtain a reflective film 221 with a reflectivity of 0.01% for a wavelength of 450 nm, the thickness of each layer of the reflective film 221 may be adjusted so as to satisfy the first film thickness condition. FIG. 4A shows a profile indicating the wavelength dependence of the reflectivity of the reflective film 221 that satisfies the first film thickness condition.

[0082] If the gain wavelength of the semiconductor laser array 200 is 440 nm and it is desired to obtain a reflective film 221 with a reflectivity of 0.01% for a wavelength of 440 nm, the thickness of each layer of the reflective film 221 may be adjusted so as to satisfy another film thickness condition.

[0083] Also, for example, if the gain wavelength of the semiconductor laser array 200 is 450 nm and it is desired to obtain a reflective film 221 with a reflectivity of 0.5% when the wavelength is 450 nm, the thickness of each layer of the reflective film 221 may be adjusted so as to satisfy the second film thickness condition. FIG. 4B shows a profile indicating the wavelength dependence of the reflectivity of the reflective film 221 that satisfies the second film thickness condition.

[0084] The reflective film 222 on the non-emitting end face of the semiconductor laser array 200 is a dielectric multilayer film formed by a combination of an SiO2 layer and an aluminum oxynitride (AlON) layer. Similar to the reflective film 221, the reflectivity of the reflective film 222 can be changed by adjusting the thickness of each layer and the refractive index of each layer. Note that the reflectivity of the reflective film 222 with respect to the laser light 1 also depends on the wavelength of the laser light 1, similar to the reflectivity of the reflective film 221.

[0085] For example, when the gain wavelength of the semiconductor laser array 200 is 450 nm and it is desired to obtain a reflective film 222 with a reflectivity of 98.7% at a wavelength of 450 nm, the thickness of each layer of the reflective film 222 may be adjusted so as to satisfy the third film thickness condition. FIG. 5 shows a profile indicating the wavelength dependence of the reflectivity of the reflective film 222 that satisfies the third film thickness condition.

[0086] <Output of Semiconductor Laser Array> When a current of 60 A is injected into the semiconductor laser array 200 according to this embodiment, a laser output can be obtained such that the sum of the laser light 1 from the emitter section 234 is 70 W or more and 88 W or less.

[0087] Since the semiconductor laser array 200 has 40 emitter sections 234, when a current of 1.5 A (that is, 60 A ÷ 40) is injected into one emitter section 234, a high laser output value of up to 2.2 W (88 W ÷ 40) can be obtained from one emitter section 234.

[0088] <Reflectivity of Reflective Film on Emitting End Face> The reflectivity of the reflective film 221 on the emitting end face will be described. In this embodiment, the reflectivity R of the reflective film 221 on the emitting end face at the gain wavelength of the semiconductor laser array 200 satisfies the relational expression (1). R1 ≦ R ≦ R(Oc) × C (1)

[0089] In relational expression (1), R1 is the reflectance of the reflection film 221 on the emission end face when the light-emitting layer 215 laser-oscillates with the power P14. The power P14 is, as shown in FIG. 6, a power that is 1.4 times the minimum threshold power Ptm, which is the minimum value of the threshold power at which the light-emitting layer 215 laser-oscillates. R(Oc) is the reflectance of the external resonance mirror 210. C is the ratio of the light 4 that is reflected by the external resonance mirror 210 and returned to the semiconductor laser array 200 and that enters the optical waveguide portion of the semiconductor laser array 200 (hereinafter referred to as the "coupling efficiency").

[0090] (Semiconductor laser element) With reference to FIG. 7, the semiconductor laser element 100 according to the present embodiment will be described. FIG. 7 is a diagram showing the semiconductor laser element 100 according to the present embodiment.

[0091] Similar to the semiconductor laser array 200, the semiconductor laser element 100 includes an n-side electrode 219, a substrate 212, a resonator structure 214, a p-side electrode 283, a reflection film 221, and a reflection film 222. In the resonator structure 214 of the semiconductor laser element 100, only one convex portion 233, that is, an emitter portion 234, is formed. The features of the other configurations of the semiconductor laser element 100 are the same as those of the semiconductor laser array 200.

[0092] It should be noted that the semiconductor laser array 200 can also be said to include a plurality of semiconductor laser elements 100 each having one emitter portion 234.

[0093] (Method for manufacturing a semiconductor laser array) Next, with reference to FIG. 8, the method for manufacturing the semiconductor laser array 200 will be described. FIG. 8 is a diagram showing the manufacturing process of the semiconductor laser array 200 according to the embodiment.

[0094] (Step S1) First, an n-type hexagonal GaN substrate (substrate 212) whose main surface is the (0001) plane is formed. Here, the thickness of the substrate 212 is, for example, 400 μm.

[0095] <Process S2> Next, a resonator structure 214 is formed on the substrate 212. Process S2 includes Process S21 and Process S22. <<Process S21>> First, a multilayer 400 is formed on the substrate 212 by crystal growth using the metalorganic chemical vapor deposition (MOCVD) method. Specifically, a first semiconductor layer 216 as a first cladding layer, a light-emitting layer 215, and a second semiconductor layer 217 are formed.

[0096] When the light-emitting layer 215 is formed of InGaN, in Process S21, by setting the In composition to about 10% or more and 17% or less, a semiconductor laser array 200 having different gain wavelengths for each emitter portion 234 can be obtained in the range of 400 nm or more and 450 nm or less.

[0097] <<Process S22>> Next, an etching mask having a width of 15 μm is formed in a stripe shape on the surface of the multilayer 400 using ordinary photolithography. Then, dry etching using a chlorine-based gas is performed on the second semiconductor layer 217 of the multilayer 400. In this etching, the etching target is the contact layer (the uppermost layer of the second semiconductor layer 217) and the cladding layer (the layer immediately below the contact layer), and the etching depth corresponds to the film thickness from the uppermost surface to the lowermost surface of the contact layer. As a result, a large number of convex portions 233 are formed in the multilayer 400.

[0098] Therefore, a resonator structure 214 is formed on the surface of the substrate 212. This resonator structure 214 has 20 emitter portions 234 with a convex portion 233 width of 15 μm and a resonator length of 2000 mm.

[0099] <Process S3> An insulating film is formed on the surface of the resonator structure 214 using a method such as CVD. This insulating film is a silicon dioxide (SiO2) layer. Next, normal photolithography is performed to remove the insulating film in a predetermined region of the convex portion 233.

[0100] On the region where the insulating film of the convex portion 233 has been removed, a p-side electrode 283 is formed using Pd and Pt as materials. Further, a pad electrode is formed so as to connect the plurality of p-side electrodes 283.

[0101] Next, the substrate 212 is polished or etched from the (000-1) plane (the back surface of the substrate 212) so that the thickness becomes about 100 μm. By thinning the substrate 212, the heat dissipation performance of the finally completed semiconductor laser array 200 can be improved.

[0102] Next, titanium and gold are deposited on the back surface of the substrate 212, and an alloy treatment is performed to form an n-side electrode 219.

[0103] <Process S4> Next, using the cleavage property of the m-plane of the substrate 212, the substrate 212 is cleaved, and a plurality of array body portions 199 including the substrate 212, the resonator structure 214, the p-side electrode 283, and the n-side electrode 219 are cut out. In this embodiment, the resonator length x is 2000 μm, the array width W is 9000 μm, and an array body portion 199 having 40 convex portions 233 is cut out.

[0104] <Process S5> Next, by laminating a SiO2 layer and an Al2O3 layer on the emission end face of the array body portion 199, a reflection film 221 having a reflectivity in a predetermined range is formed.

[0105] Also, a reflection film 222 is formed by laminating a SiO2 layer and an AlON layer on the non-emission end face of the array body portion 199.

[0106] As described above, the semiconductor laser array 200 is formed by steps S1 to S5.

[0107] Note that the semiconductor laser element 100 is obtained by dividing the array main body 199 to form an element main body having only one emitter section 234, forming a reflective film 221 on the emission end face of the element main body, and forming a reflective film 222 on the non-emission end face.

[0108] (Configuration of Laser Module) Hereinafter, with reference to FIGS. 9A and 9B, a laser module 900 on which a semiconductor laser array 200 according to the present embodiment is mounted will be described. FIG. 9A is a perspective view of the laser module 900, and FIG. 9B is an exploded perspective view of the laser module 900.

[0109] The laser module 900 is mounted on a laser oscillator 10 (see FIG. 10).

[0110] In the present embodiment, the semiconductor laser array 200 includes an upper metal block 930, a lower metal block 940, a heat conductive sheet 960, and a water cooling pedestal 970, and is configured as a high heat dissipation type module that performs cooling by water cooling. Details will be described below.

[0111] The upper metal block 930 and the lower metal block 940 are metal blocks having high heat dissipation properties, and are formed of, for example, copper. The upper metal block 930 and the lower metal block 940 are disposed above and below the semiconductor laser array 200, respectively. The heat conductive sheet 960 has insulating properties.

[0112] The laser module 900 has a structure in which the semiconductor laser array 200 can be cooled from the water cooling pedestal 970 through the heat conductive sheet 960 and the lower metal block 940.

[0113] The laser module 900 further includes a submount 920 and an insulating sheet 950. The submount 920 and the insulating sheet 950 are disposed between the semiconductor laser array 200 and the upper metal block 930 and the lower metal block 940.

[0114] Since the semiconductor laser array 200 has a plurality of emitter portions 234, the power required for laser oscillation may be several tens of W or more. Therefore, the submount 920 may be formed of a conductive material and function as a current path. For example, the submount 920 is formed of a high heat dissipation material, for example, silicon carbide.

[0115] The submount 920 may be formed of an insulating material. In this case, the surface of the submount 920 connected to the semiconductor laser array 200 may be subjected to metal plating such as gold plating and copper plating to ensure conductivity.

[0116] The upper metal block 930 and the lower metal block 940 connect the p-side electrode 283 and the n-side electrode 219 to the positive electrode and the negative electrode of a power supply device (not shown), respectively.

[0117] The beam twister unit 206 is disposed on the emission end face side of the semiconductor laser array 200. The beam twister unit 206 rotates each of the plurality of laser beams 1 emitted from the semiconductor laser array 200 by 90° to prevent mutual interference of the individual laser beams 1 having close wavelengths.

[0118] When a pulse current of 60 A is injected into the laser module 900 according to the present embodiment, laser light 1 of 60 W or more and 80 W or less can be obtained. A current of 1.5 A is injected into one emitter portion 234. As a result, a light output of up to 2.0 W (80 W÷40 (the number of emitter portions 234)) can be obtained from one emitter portion 234.

[0119] (Configuration of Laser Oscillator) The processing apparatus according to this embodiment includes a laser oscillator 10. Hereinafter, the laser oscillator 10 according to this embodiment will be described with reference to FIG. 10. FIG. 10 is a diagram showing the laser oscillator 10 used in the processing apparatus according to this embodiment. Note that the path of the cooling water and the power supply device are omitted from FIG. 10.

[0120] The laser oscillator 10 includes five laser modules 901 to 905. The above-described laser module 900 is applied to each of the laser modules 901 to 905. Further, FIG. 10 shows that semiconductor laser arrays 201 to 205 are mounted on the respective laser modules 901 to 905.

[0121] The laser oscillator 10 further includes a housing 11, a plurality of mirrors 17, a diffraction grating 208, and an external resonant mirror 210.

[0122] The housing 11 is made of, for example, stainless steel, and the laser modules 901 to 905 are arranged inside the housing 11. Actually, the laser modules 901 to 905 are arranged in a fan shape. FIG. 10 shows that they are arranged in the order of laser module 901, laser module 902, laser module 903, laser module 904, and laser module 905. Currents are injected into the laser modules 901 to 905 in series from the power supply device, and laser light 1 is emitted.

[0123] A plurality of mirrors 17, a diffraction grating 208, and an external resonant mirror 210 are arranged inside the housing 11.

[0124] The laser light 1 emitted from the laser modules 901 to 905 is condensed on the diffraction grating 208 by the plurality of mirrors 17. In this embodiment, the diffraction grating 208 is a transmission-type diffraction grating, and is arranged such that the distance (optical path length) from the emission end faces of the semiconductor laser arrays 201 to 205 to the diffraction grating 208 is 2.6 m.

[0125] The incident angle α of the laser beam 1 with respect to the diffraction grating 208 varies depending on the position of the laser module from which the laser beam 1 is emitted. The incident angles α of the laser beam 1 from the laser modules 901, 902, 903, 904, and 905 are 21.6°, 22.4°, 23.2°, 24.0°, and 24.8°, respectively, and change in increments of 0.8°. The emission angle β of the external resonance light 2 emitted from the diffraction grating 208 is 70°.

[0126] The lock wavelengths of the semiconductor laser arrays 201 to 205 in the laser oscillator 10 according to this embodiment, as well as conditions such as the groove period and lattice constant of the diffraction grating, are shown in Table 3 below.

[0127]

Table 3

[0128] The laser oscillator 10 causes resonance between the external resonance mirror 210 and the reflection film 222 on the non-emitting end faces of the semiconductor laser arrays 201 to 205, and emits a part as the laser beam 3. Note that the reflectivity of the external resonance mirror 210 is set to 15%.

[0129] In the laser oscillator 10, the coupling efficiency is set to about 15% by adjusting the optical axes of the mirror 17 and the optical components (not shown).

[0130] (Method for manufacturing a laser oscillator) The above-described laser oscillator 10 is assembled as follows. First, a housing 11 is prepared that can accommodate a plurality of laser modules 900, a diffraction grating 208, a plurality of mirrors 17, and an external resonance mirror 210, and has a capacity that allows fine adjustment of their arrangement positions.

[0131] Next, a plurality of mirrors 17, a diffraction grating 208, and an external resonant mirror 210 are arranged. At this time, the positions of the plurality of mirrors 17, the diffraction grating 208, and the external resonant mirror 210 are adjusted, and optical axis adjustment is performed so that no optical axis deviation occurs during external resonance.

[0132] Next, a plurality of laser modules 900 are prepared. Then, pre-measurement is performed on the semiconductor laser array 200 included in the prepared laser module 900. In the pre-measurement, internal resonance is generated in the semiconductor laser array 200 to cause laser oscillation.

[0133] In the pre-measurement, it is desirable to measure the gain wavelengths at the right end (one end), the left end (the other end), and the central part of the semiconductor laser array 200 at the current value used in the laser oscillator 10. When current flows, the emitter portion 234 generates heat, and the bandgap of the light-emitting layer 215 of the semiconductor laser array 200, that is, the gain wavelength changes. As a result, the gain wavelength varies depending on the position of the semiconductor laser array 200.

[0134] Also, since the output value and various characteristics change depending on the quality of the semiconductor laser array 200, it is desirable to measure the optical output at a constant current value, the threshold current, the threshold voltage, that is, the threshold power required for laser oscillation.

[0135] From the measured gain wavelength values, a laser module 900 having a semiconductor laser array 200 that matches the lock wavelength of the laser oscillator 10 is selected. At this time, it is desirable to select a laser module 900 having a semiconductor laser array 200 that can efficiently obtain optical output by internal resonance. The selected laser modules 900 are used as laser modules 901 to 905.

[0136] Next, the laser modules 901 to 905 are arranged at appropriate positions inside the housing 11. Then, the lid (not shown) of the housing 11 is closed so that scattered light does not leak outside the housing 11.

[0137] As described above, the laser oscillator 10 is completed. After that, after operating the cooling mechanism of the laser oscillator 10, the power supply of the power supply device is turned on, and the performance of the laser oscillator 10 is evaluated by measuring the output value and quality of the laser beam 3 emitted from the external resonance mirror 210.

[0138] Although the laser module 900 has been described as having the semiconductor laser array 200 (that is, a plurality of semiconductor laser elements 100), the laser module 900 may have a single semiconductor laser element 100. That is, the laser oscillator 10 may have a plurality of laser modules 900 each having only one single semiconductor laser element 100.

[0139] [Embodiment] Next, with reference to FIGS. 11 to 13, FIGS. 14A and 14B, the basis of the relational expression (1) will be described based on the embodiment.

[0140] FIG. 11 is a diagram showing the relationship between the reflectance of the reflection film 221 on the emission end face of the semiconductor laser array 200 according to the embodiment and the optical output of the laser oscillator 10 used in the processing apparatus. FIG. 12 is a view of the emitter portion 234 of the semiconductor laser array 200 according to the embodiment as viewed from the n-side electrode 219 side, showing the vicinity of the emission end face. FIG. 13 is a diagram showing the relationship between the threshold power and the reflectance of the reflection film 221 on the emission end face in the semiconductor laser array 200 according to the embodiment. The vertical axis of FIG. 13 indicates the ratio of the threshold power (hereinafter referred to as "threshold power ratio") when the minimum value of the threshold power (that is, Ptm) is 100%, and the horizontal axis of FIG. 13 indicates the reflectance of the reflection film 221 on the emission end face. FIGS. 14A and 14B are diagrams showing the wavelength spectra of the laser beam output by external resonance from the laser oscillator 10 used in the processing apparatus according to the embodiment. FIG. 14A is a spectrum obtained under the conditions that the reflectance of the reflection film 221 on the emission end face is 0.16% and the gain wavelength is 440 nm, and FIG. 14B is a spectrum obtained under the conditions that the reflectance of the reflection film 221 on the emission end face is 3.3% and the gain wavelength is 438 nm.

[0141] In this embodiment, in accordance with the above-described embodiment, the semiconductor laser array 200 was mounted on the laser module 900, and the laser oscillator 10 having a plurality of the laser modules 900 mounted thereon was manufactured.

[0142] First, ten (10) semiconductor laser arrays 200 each having the reflectivity of the reflection film 221 on the emission end face set to 0.07%, 0.16%, 0.25%, 0.35%, 0.46%, 0.55%, 0.66%, 0.75%, 0.85%, 0.95%, 1.0%, 2.2%, 3.3%, 4.0%, and 5.5% respectively were prepared (a total of 150). Note that the reflectivity of the reflection film 221 was changed by changing the film thickness configuration of the dielectric layer constituting the reflection film 221, and set to have 15 levels of reflectivity. Note that the semiconductor laser arrays 200 having the same reflectivity have substantially the same characteristics as each other and match the lock wavelength in Table 3 above.

[0143] Next, the semiconductor laser arrays 200 were mounted on the laser modules 900 one by one to form 150 laser modules 900. Then, each semiconductor laser array 200 was laser-oscillated by internal resonance. Further, at each level, five (5) laser modules 900 having the semiconductor laser array 200 in which the lock wavelength and the gain wavelength are matched were selected from among the 10 laser modules 900.

[0144] Then, using the selected laser modules 900, the laser oscillator 10 was manufactured for each of the 15 levels. Note that when arranging the selected laser modules 900, the optical axis adjustment was performed.

[0145] Thereafter, in each laser oscillator 10, the cooling mechanism was operated, the power was turned on, and the output value of the laser light 3 emitted from the external resonance mirror 210 was measured.

[0146] As shown in FIG. 11, it was confirmed that, with respect to the output value of the laser oscillator 10 when the reflectance of the reflection film 221 on the output end face is in the range of 0.35% or more and 2.2% or less, the output values when the reflectance is less than 0.35% and when the reflectance is greater than 2.2% are smaller. From this result, it can be said that in the ranges where the reflectance is less than 0.35% and greater than 2.2%, the optical output, which is the basic performance of the laser oscillator 10, decreases.

[0147] Regarding the results in FIG. 11, the inventor analyzed the reasons why the optical output value decreases as the reflectance decreases with the reflectance of 0.35% as a boundary (hereinafter referred to as "reason 1"), and the reasons why the optical output decreases as the reflectance increases with the reflectance of 2.2% as a boundary (hereinafter referred to as "reason 2").

[0148] <Cause 1> The laser module 900 was taken out from each laser oscillator 10, and the semiconductor laser array 200 was laser-oscillated by internal resonance. In the semiconductor laser array 200 having reflection films 221 with reflectances of 0.07%, 0.16%, and 0.25%, it was found that a plurality of the emitter portions 234 among the 40 emitter portions 234 were not emitting light.

[0149] Furthermore, the semiconductor laser array 200 was taken out from the laser module 900, and the emitter portions 234 of the semiconductor laser array 200 were observed from the n-side electrode 219 side.

[0150] As a result, as shown in FIG. 12, a region corresponding to the emitter portion 234 was observed. FIG. 12 shows five emitter portions 234, and among them, three non-emitting emitter portions 234 were present. Also, it was confirmed that crystal defects 600 occurred near the output end faces of the three emitter portions 234.

[0151] Note that since the n-side electrode 219 is not disposed in the region directly below the emitter portion 234 on the back surface of the substrate 212, the light emission intensity of the emitter portion 234 and the presence or absence of crystal defects 600 can be visualized.

[0152] From the results of FIG. 12, the inventor reached the following conclusion. When the reflectance of the output end face of the semiconductor laser array 200 is very small, in order to cause the semiconductor laser array 200 to oscillate by internal resonance, it is necessary to inject a relatively large amount of power into the emitter portion 234. By injecting such power, a relatively large thermal load is applied to the emitter portion 234, and crystal defects 600 are generated.

[0153] Hereinafter, the above conclusion will be described in detail.

[0154] When manufacturing the laser oscillator 10, it is necessary to examine the gain wavelength and various characteristics (for example, the output value of the laser beam 1 and semiconductor characteristics, etc.) of the prepared laser module 900 by pre-measurement. The measurement of the gain wavelength is a measurement necessary for performing the operation of selecting the laser module 900.

[0155] During the pre-measurement, it is necessary to cause the semiconductor laser array 200 to oscillate at least once by internal resonance.

[0156] When causing internal resonance in the semiconductor laser array 200, all the energy of the power supplied until the injection power reaches the threshold power is converted into thermal energy. When the thermal load inside the emitter portion 234 increases, crystal defects 600 are likely to occur at the portions where stress is applied to the resonator structure 214 and the emitter portion 234.

[0157] In the laser oscillator 10 equipped with the semiconductor laser array 200 having the emitter portion 234 including crystal defects 600, when external resonance is generated, the crystal defects 600 spread to the light emitting layer 215, and finally, the crystal constituting the light emitting layer 215 is destroyed.

[0158] <<Regarding the power at which crystal defects begin to occur>> Considering from the above conclusion, it seems that the reflectance of the reflection film 221 on the emission end face should be set so that the threshold power becomes the smallest.

[0159] Depending on the resonator length x and the shape of the emitter portion 234, the reflectance of the reflection film 221 on the emission end face showing the minimum threshold power (minimum threshold power Ptm) is different. When the semiconductor laser array 200 with a resonator length of 2000 μm is laser-oscillated by internal resonance, the reflectance of the reflection film 221 at which the threshold power is minimum is 5.5%.

[0160] Actually, in the embodiment, a semiconductor laser array 200 with a resonator length of 2000 μm has been manufactured. In the semiconductor laser array 200, as shown in FIG. 13, the threshold power showed the minimum value when the reflectance of the reflection film 221 on the emission end face was 5.5%.

[0161] However, as shown in FIG. 11, when the reflectance of the reflection film 221 is 5.5%, the optical output value of the laser oscillator 10 becomes small. Therefore, it can be said that the reflection film 221 of the semiconductor laser array 200 of the present embodiment needs to be smaller than 5.5%.

[0162] As shown in FIG. 13, in the range where the reflectance is 0.35% or less and 0.16% or more, the smaller the reflectance, the greater the tendency for the threshold power ratio to increase. Therefore, it is preferable to set 0.35%, which is the reflectance at which the optical output of the laser oscillator 10 starts to decrease, as the lower limit of the reflectance. It can be said that the threshold power at that time corresponds to the maximum value within the power range where no crystal defect 600 occurs in the emitter portion 234. According to FIG. 13, the threshold power when the reflectance is 0.35% was 1.4 times the threshold power (minimum threshold power Ptm) when the reflectance was 5.5%.

[0163] As described above, the following conclusions were obtained from FIGS. 11 to 13. When a power exceeding 1.4 times the minimum threshold power Ptm is supplied to the semiconductor laser array 200, crystal defects 600 are generated in the emitter portion 234. Since the crystal defects 600 destroyed the light emitting layer 215, the optical output of the laser oscillator 10 decreased.

[0164] Also, when the resonator length is 2000 μm, it is advisable to set the lower limit of the reflectance R to 0.35%. More generally, it is advisable to set the lower limit of the reflectance R to the reflectance of the reflection film 221 when the semiconductor laser array 200 laser oscillates at a power of 1.4 times the minimum threshold power Ptm.

[0165] <Cause 2> First, regarding the laser oscillator 10 in which the laser module 900 equipped with the semiconductor laser array 200 having the reflection film 221 with a reflectance of 3.3% is arranged, the wavelength spectrum of the laser light 3 was examined. Here, one of the five laser modules 900 of the laser oscillator 10 was laser-oscillated by external resonance, and the wavelength spectrum of the laser light 3 obtained from the laser oscillator 10 was analyzed by a spectroscope (see FIG. 14B).

[0166] Also, for comparison, regarding the laser oscillator 10 in which the laser module 900 equipped with the semiconductor laser array 200 having the reflection film 221 with a reflectance of 0.16% is arranged, the wavelength spectrum of the laser light 3 was examined in the same manner (see FIG. 14A).

[0167] The wavelength spectra of FIGS. 14A and 14B are generated by changing the lock wavelength in the range of ±3.0 nm from the gain wavelength of the laser module 900, outputting the laser light 3 at each lock wavelength, acquiring the wavelength spectrum of the laser light 3, and arranging the acquired wavelength spectra. The lock wavelength was adjusted by changing the relative orientation of the laser module 900 with respect to the diffraction grating 208.

[0168] As shown in FIG. 14A, in the wavelength spectrum with a reflectivity of 0.16%, there is no spectral peak 701 of the light obtained by internal resonance (described later), and only the spectral peak 700 of the light obtained by external resonance exists. Furthermore, it was found that the spectral peak 700 shifts to the higher wavelength side or the lower wavelength side as the lock wavelength changes. Hereinafter, such characteristics are referred to as "ideal spectral characteristics". Also, according to the wavelength spectrum of FIG. 14A, it was found that external resonance occurs even when the lock wavelength changes by ±3.0 nm.

[0169] The wavelength spectrum obtained from the laser oscillator 10 used in the WBC type processing apparatus preferably has the above-described ideal spectral characteristics.

[0170] However, as shown in FIG. 14B, in the wavelength spectrum with a reflectivity of 3.3%, it was found that a spectral peak 701 of the light obtained by internal resonance exists when the lock wavelength is shifted by ±1.5 nm from 438 nm.

[0171] Thus, it is reasonable to consider the reason for the coexistence of the spectral peak 701 caused by internal resonance and the spectral peak 700 caused by external resonance as follows. As shown in FIG. 4A, when the wavelength is shifted to the lower wavelength side by a predetermined value (a value larger than 1.5 nm) from 438 nm, the reflectivity of the reflection film 221 becomes larger than 2.2%. And at the shifted wavelength, internal resonance occurs in the semiconductor laser array 200.

[0172] When the influence of internal resonance is relatively large, the internal resonance becomes a factor in the decrease of the laser output value due to external resonance.

[0173] Therefore, when manufacturing the laser oscillator 10 using the semiconductor laser array 200 with the reflectivity of the reflection film 221 set to a value greater than a specific value, if the following factors 1 to 3 are satisfied, it can be considered that some emitter portions 234 of the semiconductor laser array 200 oscillate by internal resonance. Also, since the laser light 1 oscillated from this laser oscillation is not oscillated due to external resonance, it does not contribute to the optical output of the laser oscillator 10. Rather, it can be considered that the optical output of the laser oscillator 10 is decreased. (Factor 1) The variation in the gain wavelength for each emitter portion 234 of the semiconductor laser array 200 is greater than a certain value. (Factor 2) The variation in the reflectivity of the reflection film 221 is greater than a certain value. (Factor 3) The deviation between the gain wavelength and the lock wavelength is greater than a certain value.

[0174] The above-mentioned specific value is a value greater than approximately 2.2%, that is, a value greater than 2.225% which is the product of the reflectivity of 15% of the external resonance mirror 210 and the coupling efficiency of 15%.

[0175] For example, in this embodiment, in the laser oscillator 10 having the semiconductor laser array 200 with the reflectivity of the reflection film 221 set to 5.5%, when laser light 3 is output by external resonance, estimating from the amount of decrease in the optical output (see FIG. 11), it can be estimated that approximately 6% of the emitter portions 234 are oscillating by internal resonance.

[0176] Based on the above-mentioned matters, the inventor concluded that in this embodiment, in some of the emitter portions 234 within the laser oscillator 10, the feedback rate of internal resonance becomes larger than that of external resonance, and the optical output decreases. Further, the inventor concluded that the reflectivity that coincides with the product of the reflectivity of the external resonance mirror 210 and the coupling efficiency C is the critical point at which the optical output value of the laser oscillator 10 begins to decrease, and it is advisable to determine that critical point as the upper limit. From this, by satisfying the relational expression (1) for the reflectivity R of the reflection film 221 on the output end face, pre-measurement can be performed without generating crystal defects 600 in the semiconductor laser array 200, and when oscillating the laser beam 3 by external resonance, the influence of internal resonance can be suppressed to a minimum, so it is concluded that a decrease in the laser output value can be suppressed.

[0177] In this embodiment, it was implemented based on the embodiment of the semiconductor laser array 200, but even when the semiconductor laser element 100 is used, the same conclusion can be drawn.

[0178] As described above, the semiconductor laser element 100 according to the embodiment is a semiconductor laser element 100 disposed in a laser oscillator 10 provided in a processing apparatus of a WBC having an external resonance mirror 210, and includes a resonator structure 214 having a light-emitting layer 215 that emits a laser beam 1, and a reflection film 222 and a reflection film 221 that are respectively provided on the non-output end face and the output end face of the resonator structure 214 and reflect the laser beam 1. Further, when the resonator structure 214 oscillates in laser at a power P14 that is 1.4 times the minimum value of the threshold power (minimum threshold power Ptm) which is the minimum power at which the resonator structure 214 laser oscillates, the reflectivity of the reflection film 221 is R1, the reflectivity of the external resonance mirror 210 is R(Oc), and the coupling efficiency which is the ratio at which the reflected light from the external resonance mirror 210 enters the resonator structure 214 is C, the reflectivity R of the reflection film 221 at the gain wavelength of the semiconductor laser element 100 satisfies the above-mentioned relational expression (1).

[0179] The laser oscillator 10 provided in the processing apparatus according to the embodiment includes a laser module 900 including a single semiconductor laser element 100.

[0180] As described in the embodiments, according to the embodiment, when manufacturing the laser oscillator 10 using the semiconductor laser element 100, even if laser oscillation is caused by internal resonance in the pre-measurement, crystal defects do not occur in the semiconductor laser element 100. Therefore, the laser output value of the laser oscillator 10 does not decrease. Also, when laser light 3 is oscillated by external resonance in the laser oscillator 10, since the influence of internal resonance on the optical output of external resonance is small, a decrease in the laser output value of the laser oscillator 10 due to internal resonance is suppressed. Therefore, laser light 3 suitable for the laser oscillator 10 used in the processing apparatus can be obtained.

[0181] Therefore, it is possible to increase the output power of the laser oscillator 10, and thus increase the output power of the processing apparatus.

[0182] Also, since it is not necessary to incorporate the semiconductor laser element 100 having crystal defects into the laser oscillator 10, the output value of the laser oscillator 10, that is, the processing apparatus can be stabilized.

[0183] Even if pre-measurement is performed, the semiconductor laser element 100 according to the present embodiment does not generate crystal defects in each emitter section 234, so special measurement and analysis for examining the presence of crystal defects are unnecessary. Therefore, the laser oscillator 10 with a stable laser output value can be easily manufactured.

[0184] The semiconductor laser array 200 according to the embodiment includes a plurality of the above-described semiconductor laser elements 100. Also, the laser oscillator 10 included in the processing apparatus according to the embodiment includes a laser module 900 including the semiconductor laser array 200. Therefore, the same effects as in the case of manufacturing the laser oscillator 10 using the semiconductor laser element 100 can be obtained.

[0185] Also, it is difficult to detect crystal defects existing in each emitter section 234 of the semiconductor laser array 200 by measurement or analysis from the end of the pre-measurement until the semiconductor laser array 200 is incorporated into the laser oscillator 10. Naturally, it can also be said that it is difficult to select and remove only the emitter sections 234 in which crystal defects have occurred from the semiconductor laser array 200 before incorporating it into the laser oscillator 10.

[0186] As described above, even if pre-measurement is performed, in the semiconductor laser array 200 according to the present embodiment, crystal defects do not occur in each emitter section 234, so special measurement and analysis for examining the presence of crystal defects are unnecessary. Therefore, a laser oscillator 10 with a stable laser output value can be easily manufactured.

[0187] The semiconductor laser array 200 according to the embodiment is a component configured by a set of a plurality of semiconductor laser elements 100. That is, the semiconductor laser array 200 is a component having a plurality of laser light sources. Therefore, compared with the case where a laser module 900 is manufactured for each semiconductor laser element 100 and the laser module 900 is incorporated into the laser oscillator 10, the number of laser modules 900 to be incorporated into the laser oscillator 10 can be reduced.

[0188] [Modification Example 1] Hereinafter, regarding Modification Example 1, mainly the differences from the embodiment will be described.

[0189] The reflection film 221 included in the semiconductor laser element 100 and the semiconductor laser array 200 according to Modification Example 1 has less variation in reflectance compared to the reflection film 221 of the embodiment. That is, the reflection film 221 according to Modification Example 1 has a constant reflectance regardless of the position. Also, the deviation between the gain wavelength and the lock wavelength in the laser oscillator 10 used in the processing apparatus according to Modification Example 1 is smaller than the deviation between the gain wavelength and the lock wavelength in the laser oscillator 10 used in the processing apparatus according to the embodiment.

[0190] In Modification 1, in order to reduce the variation in the reflectance of the reflection film 221, the thicknesses of the respective layers (dielectric layers) constituting the reflection film 221 are precisely controlled. Further, in order to reduce the deviation between the gain wavelength and the lock wavelength, when selecting the laser module 900 incorporated in the laser oscillator 10, a laser module 900 having a semiconductor laser element 100 or a semiconductor laser array 200 with a smaller deviation between the gain wavelength and the lock wavelength is selected.

[0191] The reflectance R of the reflection film 221 on the emission end face at the gain wavelength of the semiconductor laser element 100 and the semiconductor laser array 200 according to Modification 1 satisfies the relational expression (2). That is, the upper limit of the reflectance R in Modification 1 is twice the upper limit of the reflectance R in the embodiment. R1≦R≦2×R(Oc)×C (2)

[0192] Hereinafter, the basis of the relational expression (2) will be described.

[0193] <Another upper limit (1) in the embodiment> Based on the results of the embodiment, the inventor further intensively studied the upper limit of the reflectance of the reflection film 221 on the emission end face. The details will be described below.

[0194] The laser oscillator 10 was manufactured such that the variation in the reflectance of the reflection film 221 on the emission end face of the semiconductor laser array 200 and the deviation between the gain wavelength and the lock wavelength were reduced. Specifically, by precisely controlling the thicknesses of the respective layers (dielectric layers) constituting the reflection film 221, the variation in the reflectance of the reflection film 221 on the emission end face was reduced. Further, by selecting a semiconductor laser array 200 having a gain wavelength closer to the lock wavelength, the deviation between the gain wavelength and the lock wavelength was reduced.

[0195] As a result, it was confirmed that even when the reflectance of the reflection film 221 on the emission end face was set to a value that matches twice the product of the reflectance of the external resonance mirror 210 of the laser oscillator 10 and the coupling efficiency, i.e., 2.225% (1.5% × 1.5%), the optical output value of the laser oscillator 10 did not decrease.

[0196] That is, it was confirmed that if the variation in the reflectivity of the reflection film 221 on the emission end face of the semiconductor laser array 200 and the deviation between the gain wavelength and the lock wavelength can be reduced, even if the reflectivity of the reflection film 221 is relatively large, the optical output value of the laser oscillator 10 does not decrease.

[0197] The result of the intensive study on the above-mentioned another upper limit (1) is the same even when the semiconductor laser element 100 is used.

[0198] As described above, according to the first modification, even if the reflectivity of the reflection film 221 on the emission end face is set to a relatively large value, since the reflectivity R of the reflection film 221 on the emission end face satisfies the relational expression (2), the influence of internal resonance can be suppressed to a small level, and the output value of the laser oscillator 10, that is, the output value of the processing apparatus does not decrease.

[0199] [Second Modification] Hereinafter, the main differences from the first modification will be mainly described for the second modification.

[0200] The reflection film 221 on the emission end face of the semiconductor laser element 100 and the semiconductor laser array 200 according to the second modification has less variation in reflectivity compared to the reflection film 221 of the first modification. Also, the deviation between the gain wavelength and the lock wavelength in the laser oscillator 10 used in the processing apparatus according to the second modification is smaller than the deviation between the gain wavelength and the lock wavelength in the laser oscillator 10 used in the processing apparatus according to the first modification.

[0201] In the second modification, the thickness of each layer (dielectric layer) constituting the reflection film 221 on the emission end face is more strictly controlled. Also, when selecting the laser module 900 incorporated in the laser oscillator 10, a laser module 900 having a semiconductor laser element 100 or a semiconductor laser array 200 with a gain wavelength whose lock wavelength coincides or is even closer is selected.

[0202] Furthermore, during the generation of the resonator structure 214, the distribution of the growth temperature of the light-emitting layer 215 is suppressed. As a result, the variation in the gain wavelengths of the plurality of emitter portions 234 finally formed is reduced. Also, the gain wavelengths of the plurality of emitter portions 234 become the same as or a value relatively close to the lock wavelength of the laser oscillator 10.

[0203] The reflectance R of the reflective film 221 on the output end face at the gain wavelength of the semiconductor laser element 100 and the semiconductor laser array 200 according to Modification 2 satisfies the relational expression (3). That is, the upper limit of the reflectance R of the output end face of Modification 2 is three times the upper limit of the reflectance R of the embodiment. R1 ≦ R ≦ 3×R(Oc)×C (3)

[0204] Hereinafter, the basis of the relational expression (3) will be described.

[0205] <Another upper limit in the embodiment (2)> Based on the results of the embodiment and the results of the above-described another upper limit (1), the inventor further intensively studied the upper limit of the reflectance of the reflective film 221 on the output end face. The details will be described below.

[0206] The laser oscillator 10 was manufactured such that the variation in the reflectance of the reflective film 221 of the semiconductor laser array 200 and the deviation between the gain wavelength and the lock wavelength were further reduced.

[0207] Specifically, the variation in the reflectance of the reflective film 221 on the output end face was reduced by more precisely controlling the thickness of each layer (dielectric layer) constituting the reflective film 221 on the output end face. Also, the deviation between the gain wavelength and the lock wavelength was further reduced by selecting a semiconductor laser array 200 having a gain wavelength that coincides with or is even closer to the lock wavelength of the laser oscillator 10.

[0208] Furthermore, during the manufacture of the semiconductor laser array 200, the distribution of the growth temperature of the light-emitting layer 215 was suppressed to reduce the variation in the gain wavelength of the plurality of emitter portions 234 finally formed. As a result, the gain wavelengths of the plurality of emitter portions 234 became the same as or relatively close to the lock wavelength of the laser oscillator 10.

[0209] As a result, even when the reflectance of the reflection film 221 on the output end face was set to a value such that the product of the reflectance of the external resonator mirror 210 of the laser oscillator 10 and the coupling efficiency was equal to three times 2.225% (1.5% × 1.5%), it was confirmed that the optical output value of the laser oscillator 10 did not decrease.

[0210] That is, it was confirmed that if the variation in the reflectance of the reflection film 221 on the output end face of the semiconductor laser array 200 and the deviation between the gain wavelength and the lock wavelength could be further reduced, the optical output value of the laser oscillator 10 would not decrease even if the reflectance of the reflection film 221 was set relatively large.

[0211] The result of the intensive study regarding the above-described another upper limit (2) is the same even when the semiconductor laser element 100 is used.

[0212] As described above, according to Modification 2, even if the reflectance of the reflection film 221 on the output end face is set to an even larger value, since the reflectance R of the reflection film 221 on the output end face satisfies the relational expression (3), the influence of internal resonance can be suppressed to a small level, and the output value of the laser oscillator 10, that is, the output value of the processing apparatus does not decrease.

[0213] [Modification 3] Hereinafter, regarding Modification 3, mainly the differences from the embodiment will be described.

[0214] The gain wavelength of the light-emitting layer 215 of the semiconductor laser element 100 and the semiconductor laser array 200 according to Modification 3 is in the range of 350 nm or more and 450 nm or less, and the resonator length is in the range of 1200 μm or more and 3000 μm or less.

[0215] Also, when the resonator length is x, the reflectivity R of the reflection film 221 on the emission end face at the gain wavelength of the semiconductor laser element 100 or the semiconductor laser array 200 satisfies the relational expression (4). R ≦ 0.3568e -0.001x (4)

[0216] Also, the reflectivity R further satisfies the relational expression (5). 0.8613e -0.003x ≦ R (5)

[0217] The range of the reflectivity R that satisfies the relational expressions (4) and (5) is a numerically achievable range in the manufacture of the reflection film 221. Therefore, according to Modification 3, if the configuration of the semiconductor laser element 100 or the semiconductor laser array 200 to be manufactured, and the laser oscillator 10 (particularly, the resonator length) are determined in advance, by setting the reflectivity R of the reflection film 221 so as to satisfy the relational expressions (4) and (5) according to the resonator length, the same effects as those of the embodiment can be obtained. Note that as long as the resonator length is set to be 1200 μm or more and 3000 μm or less, the upper limit value calculated based on the relational expression (4) will not be smaller than the lower limit value calculated based on the relational expression (5).

[0218] When the semiconductor laser element 100 and the semiconductor laser array 200 are formed of a nitride semiconductor and include a light-emitting layer 215 having a gain wavelength of 350 nm or more and 480 nm or less as in Modification 3, a high optical output value can be obtained in the range where the resonator length is 1200 μm or more and 3000 μm or less. Furthermore, crystal defects are more likely to occur in the light-emitting layer 215 formed of a nitride semiconductor during pre-measurement than in a light-emitting layer formed of other materials such as GaAs or InP.

[0219] That is, according to Modification 3, even if the semiconductor laser element 100 and the semiconductor laser array 200 are formed of a material in which crystal defects are relatively likely to occur, by setting the reflectivity of the reflection film 221 so as to satisfy the relational expressions (4) and (5), the same effects as those of the embodiment can be surely obtained.

[0220] Next, the reason why the above effects are obtained will be explained with Modification 3.

[0221] Based on the results of the embodiments, the inventor intensively studied the upper and lower limits of the reflectance of the ideal output end face reflective film 221 for the semiconductor laser array 200, which has different resonator lengths and the other configurations are the same as those of the semiconductor laser array 200 in the embodiments.

[0222] First, the inventor estimated the upper and lower limits of the reflectance of the output end face reflective film 221 when the resonator lengths were 1200 μm, 1500 μm, and 3000 μm.

[0223] Here, as the lower limit, the inventor estimated the minimum reflectance at which crystal defects 600 do not occur in the semiconductor laser array 200 and the optical output value of the laser oscillator 10 does not decrease even when laser oscillation is caused by internal resonance, based on the following (a) to (c). (a) In the range where the reflectance of the output end face reflective film 221 is relatively small, the threshold power tends to increase as the reflectance of the reflective film 221 decreases (see Fig. 13) (b) The lower limit when the resonator length is 2000 μm (results of the embodiments) (c) The relationship between the resonator length and the threshold power

[0224] Also, as the upper limit, when the laser light 3 is output from the laser oscillator 10 by external resonance, the inventor estimated the maximum value of the reflectance at which internal resonance does not occur in the emitter portion 234 of the semiconductor laser array 200 and the optical output value of the laser oscillator 10 does not decrease, based on the following (d) to (e). (d) The longer the resonator length, the smaller the optimal reflectance of the external resonance mirror 210 tends to be (e) The optimal reflectance of the external resonance mirror 210 when the resonator length is 2000 μm (5.6%)

[0225] FIG. 15 is a diagram showing the relationship between the upper and lower limits of the reflectance of the reflection film 221 on the emission end face and the resonator length. In FIG. 15, in addition to the upper and lower limits obtained in the examples (both values obtained by experiments), the upper and lower limits (both estimated values) when the resonator lengths are 1200 μm, 1500 μm, and 3000 μm are plotted.

[0226] When the data of the plurality of upper limits and the data of the plurality of lower limits in FIG. 15 are respectively fitted, the upper limit function is 0.3568e -0.001x represented by, and the lower limit function is 0.8613e -0.003x It was found that it is represented by.

[0227] That is, when the semiconductor laser array 200 satisfies at least the following conditions 1 and 2, when the reflectance of the reflection film 221 is R, by setting the value of the reflectance of the reflection film 221 so as to satisfy the above relational expressions (4) and (5), it has been found that the laser oscillator 10 can output higher-power laser light 3. (Condition 1) The semiconductor laser array 200 has a light-emitting layer 215 in which the gain wavelength ranges from 350 nm to 450 nm. (Condition 2) The semiconductor laser array 200 has an emitter portion 234 in which the resonator length ranges from 1200 μm to 3000 μm.

[0228] When the reflectance R of the reflection film 221 on the emission end face satisfies the above relational expressions (4) and (5), even if laser oscillation is caused by internal resonance in pre-measurement, crystal defects 600 are less likely to occur in the semiconductor laser array 200, and it can be said that a decrease in the laser output value of the laser oscillator 10 due to the crystal defects 600 can be prevented. Also, when the laser oscillator 10 is laser-oscillated by external resonance, it can be said that a decrease in the output value of the laser light 3 due to internal resonance can be prevented.

[0229] Furthermore, since crystal defects 600 are less likely to occur in the semiconductor laser array 200, it is not necessary to use the semiconductor laser array 200 including crystal defects 600 in the manufacture of the laser oscillator 10, so it can be said that the laser output value from the laser oscillator 10 is stabilized.

[0230] Incidentally, the results of intensive studies on the upper and lower limits of the reflectance of the reflection film 221 on the emission end face described above are the same even when the semiconductor laser element 100 is used.

[0231] [Other Modification Examples] The semiconductor laser array 200 according to the present embodiment, Modification Examples 1 and 2 has been described as a GaN-based semiconductor laser array that uses a GaN-based compound as a material and emits laser light 1 in a wavelength band of 405 nm or more and 450 nm or less. However, the material and the wavelength band are not limited to this. Even when the semiconductor laser array 200 according to the present embodiment, Modification Examples 1 and 2 employs a GaN-based semiconductor laser array, for example, a semiconductor laser array that emits laser light 1 in a wavelength band of 350 nm or more and 405 nm or less (blue-violet to ultraviolet) may be used.

[0232] Further, the semiconductor laser array 200 according to the present embodiment and Modification Examples 1 to 3 may be a semiconductor laser array using another III-V group semiconductor material such as GaAs or InP as a material.

[0233] The content described in the above other modification examples is the same not only for the semiconductor laser array 200 but also for the semiconductor laser element 100 according to the present embodiment and Modification Examples 1 to 3.

Industrial Applicability

[0234] According to the present disclosure External resonance type laser oscillator and the processing apparatus are suitable for a wavelength beam combining type processing apparatus.

Description of Reference Numerals

[0235] 1 Laser light 2 External resonance light 3 Laser light 4 Light 10 Laser oscillator 11 Housing 17 Mirror 100 Semiconductor laser element 199 Array main body 200 - 205 Semiconductor laser array 206 Beam twister unit 208 Diffraction grating 210 External resonant mirror 212 Substrate 214 Resonator structure 215 Light - emitting layer 216 First semiconductor layer 217 Second semiconductor layer 219 n - side electrode 221 Reflective film 222 Reflective film 233 Convex part 234 Emitter part 283 p - side electrode 400 Multilayer 600 Crystal defect 700 Spectrum peak 701 Spectrum peak 900 - 905 Laser module 920 Sub - mount 930 Upper metal block 940 Lower metal block 950 Insulating sheet 960 Thermal conduction sheet 970 Water - cooling stand x Resonator length L Distance α Incident angle β Exit angle

Claims

1. An external resonance type laser oscillator, comprising: a semiconductor laser element; an external resonance mirror; wherein the semiconductor laser element includes a resonator structure having a light emitting layer that emits laser light, a first reflective film and a second reflective film respectively provided on a non-emitting end face and an emitting end face of the resonator structure to reflect the laser light; wherein the external resonance mirror causes external resonance with the first reflective film, when the resonator structure laser oscillates at a power that is 1.4 times the minimum value of the threshold power which is the minimum power at which the resonator structure laser oscillates, taking the reflectivity of the second reflective film as R1, the reflectivity of the external resonance mirror as R( Oc), and the coupling efficiency which is the ratio of the reflected light from the external resonance mirror incident on the resonator structure as C, the reflectivity R of the second reflective film at the gain wavelength of the semiconductor laser element satisfies R1 ≤ R ≤ R( Oc) × C An external resonance type laser oscillator satisfying the relational expression shown above.

2. An external resonance type laser oscillator, comprising: a semiconductor laser element; an external resonance mirror; wherein the semiconductor laser element includes a resonator structure having a light emitting layer that emits laser light, a first reflective film and a second reflective film respectively provided on a non-emitting end face and an emitting end face of the resonator structure to reflect the laser light; wherein the external resonance mirror causes external resonance with the first reflective film, when the resonator structure laser oscillates at a power that is 1.4 times the minimum value of the threshold power which is the minimum power at which the resonator structure laser oscillates, taking the reflectivity of the second reflective film as R1, the reflectivity of the external resonance mirror as R( Oc), and the coupling efficiency which is the ratio of the reflected light from the external resonance mirror incident on the resonator structure as C, the reflectivity R of the second reflective film at the gain wavelength of the semiconductor laser element satisfies R1 ≤ R ≤ 2 × R( Oc) × C An external resonance type laser oscillator satisfying the relational expression shown above.

3. An external resonance type laser oscillator, comprising: a semiconductor laser element; an external resonance mirror; wherein the semiconductor laser element includes a resonator structure having a light emitting layer that emits laser light, a first reflective film and a second reflective film respectively provided on a non-emitting end face and an emitting end face of the resonator structure to reflect the laser light; wherein the external resonance mirror causes external resonance with the first reflective film, When the resonator structure oscillates lasing at a power that is 1.4 times the minimum value of the threshold power, which is the minimum power at which the resonator structure oscillates lasing, let the reflectivity of the second reflective film be R1, the reflectivity of the external resonant mirror be R(OC), and the coupling efficiency, which is the ratio at which the reflected light from the external resonant mirror enters the resonator structure, be C. Then, the reflectivity R of the second reflective film at the gain wavelength of the semiconductor laser element is R1 ≤ R ≤ 3 × R(OC) × C An external resonant laser oscillator that satisfies the relational expression shown.

4. Comprising a semiconductor laser array having a plurality of the semiconductor laser elements The external resonant laser oscillator according to any one of Claims 1 to 3.

5. Comprising the external resonant laser oscillator according to any one of Claims 1 to 3 A wavelength beam combining processing apparatus.

6. Comprising the external resonant laser oscillator according to Claim 4 A wavelength beam combining processing apparatus.

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