JP2021136317A - Semiconductor laser device - Google Patents

Abstract

An external cavity type semiconductor laser device including a plurality of semiconductor laser elements is provided, in which the oscillation thresholds of the plurality of semiconductor laser elements can be brought close to each other. A semiconductor laser device 100 includes a semiconductor laser element 10 that has a ridge part 10R and emits light 400, and a semiconductor laser element that has a ridge part 11R and emits light 401 having a longer wavelength than light 400. 11, and an external resonator that causes light 400 to resonate between the semiconductor laser element 10 and light 401 to resonate between the semiconductor laser element 11. When viewed from the stacking direction, the width L0 of the ridge portion 10R at the first end face (output end face 240) which emits the light 400 in the semiconductor laser element 10 is equal to the width L0 of the ridge portion 10R at the first end face (output end face 240) which emits the light 401 in the semiconductor laser element 11. The width L1 of the ridge portion 11R at the output end surface 240) is smaller than the width L1 of the ridge portion 11R. [Selection diagram] Figure 3

Description

The present disclosure relates to an external cavity type semiconductor laser device.

Conventionally, there is a semiconductor laser apparatus used as a light source for laser processing. High light output is required for this type of semiconductor laser device. Therefore, in order to obtain a high light output, there is a method in which a plurality of laser beams are combined so as to pass through one optical path, that is, a plurality of laser beams are combined (see, for example, Patent Document 1).

Further, conventionally, in order to improve the light output, an external resonator type semiconductor laser that resonates the light emitted by the semiconductor laser element between the semiconductor laser element and an optical system such as a half mirror and emits it as laser light. There is a device.

Here, in order to externally resonate the light with the plurality of semiconductor laser elements using an optical system such as a half mirror and emit the laser light from the semiconductor laser device, the light is input to each of the plurality of semiconductor laser elements. The amount of current that needs to be generated may differ depending on the wavelength of light emitted by the plurality of semiconductor laser elements. This is because the oscillation thresholds of the plurality of semiconductor elements are different. In order to apply different current amounts to each of the plurality of semiconductor laser elements, the structure becomes complicated as compared with the case where the same amount of current is applied to each of the plurality of semiconductor laser elements.

Japanese Patent No. 5981855

J. Piprek and S. Nakamura, Physics of high-power InGaN = GaN lasers, IEE Proc. -Optorector. , Vol. 149, No. 4, August 2002 S. K. Puch, D.M. J. Dugdale, S.M. Brand, and R. A. Abram, Band-gap and k. p. parameters for GaAlN and GaInN alloys, Journal of Applied Physics 86, 3768 (1999), 25 January 1999 Larry A. Coldren, Translated by Tatsuya Kimura, Semiconductor Lasers and Photonics Integrated Circuits, Ohmsha, Chapter 2, 2.5

The present disclosure provides a semiconductor laser device capable of approaching the oscillation thresholds of each of the plurality of semiconductor laser elements in an external resonator type semiconductor laser device including a plurality of semiconductor laser elements.

The semiconductor laser device according to one aspect of the present disclosure is a semiconductor laser device including a plurality of semiconductor laser devices in which a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are laminated in this order. The semiconductor laser device has a first stripe structure for narrowing the current flowing through the first active layer, and narrows the first semiconductor laser device that emits the first light and the current flowing through the second active layer. The semiconductor laser device includes a second semiconductor laser device that has a second stripe structure for emitting a second light having a wavelength longer than that of the first light, and the semiconductor laser device is between the first semiconductor laser device and the device. The first semiconductor laser device is provided with an external resonator that resonates the first light and resonates the second light with the second semiconductor laser device when viewed from the stacking direction. The width of the first stripe structure, which is the width of the first stripe structure on the first end surface that emits the first light, is the width of the second stripe structure on the second end surface that emits the second light in the second semiconductor laser device. It is smaller than the width of the second stripe, which is the width of.

According to the present disclosure, in an external resonator type semiconductor laser device including a plurality of semiconductor laser elements, it is possible to provide a semiconductor laser device capable of approaching the oscillation thresholds of the plurality of semiconductor laser elements.

FIG. 1 is a top view showing a semiconductor laser device according to a comparative example. FIG. 2 is a top view showing the semiconductor laser device according to the embodiment. FIG. 3 is a top view showing the semiconductor laser device according to the embodiment. FIG. 4 is a cross-sectional view showing a semiconductor laser device according to an embodiment in the IV-IV line of FIG. FIG. 5 is a graph showing an oscillation threshold current density with respect to an oscillation wavelength in the semiconductor laser device according to the embodiment. FIG. 6 is a graph showing a stripe width with respect to an oscillation wavelength in the semiconductor laser device according to the embodiment. FIG. 7A is a schematic cross-sectional view showing the first step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7B is a schematic cross-sectional view showing a second step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7C is a schematic cross-sectional view showing a third step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7D is a schematic cross-sectional view showing a fourth step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7E is a schematic cross-sectional view showing a fifth step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7F is a schematic cross-sectional view showing a sixth step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 8 is a top view showing a semiconductor laser device according to a modified example.

(Knowledge on which this disclosure was based)
The semiconductor laser apparatus according to the present disclosure is used, for example, as a light source for laser processing.

Laser processing is attracting attention as a means for performing clean welding, cutting, modification, etc. on materials to be processed such as metals, resins, and carbon fibers with good controllability. According to laser processing, for example, high-quality processing can be realized because spot welding can be performed in a smaller size than arc discharge, and chip generation can be suppressed as compared with cutting using a mold.

In a laser processing machine that performs such laser processing, a DDL (Direct IDE Laser) method that directly uses a laser beam emitted from a semiconductor laser device may be adopted.

The DDL method is highly efficient because it does not convert (i) laser light, and (b) the wavelength ranges from ultraviolet to infrared by appropriately selecting the material used for the semiconductor laser element included in the semiconductor laser device. It has two features that it can be processed with any laser beam of. In recent years, in the DDL method, a semiconductor laser device using a nitride semiconductor (GaN, InGaN, AlGaN, etc.) and equipped with a semiconductor laser element that emits a laser beam having a wavelength in the 400 nm band can process copper with high efficiency. It is receiving particular attention.

Generally, by widening the width of the emitter (for example, the width of the ridge portion) which is the light emitting portion (active layer) of the semiconductor laser element, the electric power that can be input to the light emitting portion can be increased.

Thereby, the output (optical output) of the semiconductor laser element can be increased.

However, the luminous efficiency of the semiconductor laser device is 30% to 50%. Electric power that does not contribute to light emission becomes heat and raises the temperature of the emitter. This temperature rise causes thermal saturation due to light emission in the semiconductor laser element, which adversely affects the improvement of the output of the semiconductor laser element.

Therefore, there is a semiconductor laser array having an array structure (also referred to as a multi-emitter) in which a plurality of emitters are formed on one substrate.

In a semiconductor laser array, in order to use a plurality of laser beams emitted from each emitter for processing, it is necessary to combine the plurality of laser beams into one laser beam. For example, a plurality of laser beams emitted from different light emitting points in a semiconductor laser array need to irradiate the material to be processed at one point. Therefore, for example, it is necessary to align the optical axes of a plurality of laser beams.

For example, there is a wavelength synthesis method as a method of aligning a plurality of laser beams on one optical axis (in other words, collecting them so as to pass through one optical path). The wavelength synthesis method is a method of collecting the same optical axes of the respective optical axes of a plurality of laser beams emitted from a semiconductor laser array, and has high beam quality (for example, light spots of a plurality of laser beams in a material to be processed). The position and shape of the laser are easily aligned).

Here, the principle of the wavelength synthesis method will be described.

When N laser beams are incident on a diffraction grating having a period d, the wavelength of each laser beam is λi, and the incident angle of the laser light incident on the diffraction grating is θi, (i = 1, 2, ..., When N) is set and any integer other than 0 is set to m, the following equation (1) is satisfied.

d × (sinθi + sinθ0) = mλi equation (1)

If the above equation (1) is satisfied, it is derived as a general diffraction phenomenon that the laser beam is emitted in the direction of the emission angle θ0. That is, a plurality of laser beams can be combined (combined) coaxially (that is, on one optical axis) without degrading the beam quality.

A comparative example of a semiconductor laser device by such a wavelength synthesis method will be described.

FIG. 1 is a top view showing a semiconductor laser device according to a comparative example.

The semiconductor laser array 1000 having the semiconductor laser elements 1010, 1011 and 1012 according to the comparative example shown in FIG. 1 is a GaN (Gallium Nitride) -based semiconductor laser element. Further, a comparative example described below is an external resonator type wavelength synthesis method in which the semiconductor laser array 1000 and the output coupler (optical system such as a half mirror) resonate externally. In FIG. 1, the output coupler is used. The illustration is omitted.

In the wavelength synthesis method using external resonance, a plurality of semiconductor laser elements 1010, 1011 and 1012 are aligned (in the comparative example shown in FIG. 1, the semiconductor laser array 1000), and the collimator optical system (collimeter lens) 1060 and the diffraction grating are arranged. The wavelength dispersion element (not shown) included is arranged between the semiconductor laser array 1000 and the output coupler.

As a result, a plurality of lights having different wavelengths are superimposed on the output coupler. A part of the light superimposed by the output coupler is reflected from the output coupler toward the semiconductor laser array 1000, passes through the path (optical path) opposite to the outward path, and returns to the semiconductor laser array 1000.

In the above-mentioned Patent Document 1, wavelength synthesis using a near-infrared wavelength arsenide semiconductor (GaAs (Gallium Arsenide), AlGaAs (Aluminium Gallium Arsenide), InGaAs (Indium Gallium Arsenide), etc.) and adopting the DDL method. A legal system has been proposed. When combining light from each of a large number of emitters as in the system disclosed in Patent Document 1, it is important to emit light of uniform and high output from each emitter. In the configuration disclosed in Patent Document 1, a part of the light incident on the output coupler is directed from the output coupler to the semiconductor laser element, specifically, the optical system is directed to the semiconductor laser element by the path opposite to the outward path. Such light that returns with is collected by the collimator optical system and irradiates the end face of the semiconductor laser element.

Here, even if the collimator optical system is the same, since the wavelength of the returning light is a different wavelength selected by the wavelength dispersion optical system (diffraction grating), the light emitted from the collimator lens to the end face of the semiconductor laser element. Have different focal depths.

For example, as shown in FIG. 1, the light 1040 reflected by the output coupler is incident on the semiconductor laser element 1010. Further, the light 1041 reflected by the output coupler is incident on the semiconductor laser element 1011. The light 1042 reflected by the output coupler is incident on the semiconductor laser element 1012. The lights 1040, 1041 and 1042 have different wavelengths depending on, for example, a wavelength dispersion element. Here, as shown in FIG. 1, since the spread width of the light on the end faces of the semiconductor laser elements 1010, 1011 and 1012 differs depending on the wavelengths of the light 1040, 1041 and 1042, the semiconductor laser elements 1010, 1011 and 1012 are each. The proportion of light coupled to the waveguide mode in the waveguides 1030, 1031 and 1032 differs for each of the semiconductor laser elements 1010, 1011 and 1012.

Further, even if the width of the light returning to the semiconductor laser element that oscillates at a certain wavelength is designed so that the coupling efficiency to the waveguide mode is high, the coupling efficiency is high in the semiconductor laser element that oscillates at another wavelength. Since the appropriate width of the laser beam to be increased is different, the coupling efficiency is not increased.

As a result of diligent studies, the inventors of the present application set the size of the waveguide of the semiconductor laser device appropriately according to the wavelength of the emitted light, thereby adjusting the coupling efficiency of the waveguide mode in the waveguide to the wavelength of the light. We found that it can be kept large regardless. Further, as a result of diligent studies, the inventors of the present application have found that the oscillation threshold value can be adjusted by appropriately setting the size of the stripe structure for narrowing the current applied to the semiconductor laser device.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be noted that all of the embodiments described below show a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, the arrangement positions of the components, the connection form, and the like shown in the following embodiments are examples and are not intended to limit the present disclosure.

Further, each figure is a schematic view and is not necessarily exactly illustrated. Therefore, the scales and the like do not always match in each figure. In each figure, substantially the same configuration is designated by the same reference numerals, and duplicate description will be omitted or simplified.

Further, in the present specification, the terms "upper" and "lower" do not refer to the upward direction (vertically upward) and the downward direction (vertically downward) in absolute spatial recognition, but are based on the stacking order in the stacking configuration. It is used as a term defined by the relative positional relationship with. Also, the terms "upper" and "lower" are used not only when the two components are spaced apart from each other and another component exists between the two components, but also when the two components It also applies when they are placed in contact with each other.

Further, in the present specification, the X-axis, the Y-axis and the Z-axis indicate the three axes of the three-dimensional Cartesian coordinate system. In each embodiment, the Z-axis direction is the vertical direction, and the direction perpendicular to the Z-axis (the direction parallel to the XY plane) is the horizontal direction. Further, in the present specification, the Z-axis positive direction may be described as upward, and the Z-axis negative direction may be described as downward. Further, in the present specification, the direction in which the semiconductor laser device emits light may be described as the Y-axis positive direction.

Further, in the present specification, the numerical values described for dimensions and the like not only mean that they are completely the numerical values, but also mean that they include a difference of about several percent, for example, 5%.

(Embodiment)
[Configuration of semiconductor laser device]
FIG. 2 is a top view showing the semiconductor laser device according to the embodiment.

The semiconductor laser device 100 is a light source that outputs laser light. The laser light has a wavelength of, for example, about 400 nm to 450 nm, and a plurality of laser lights are combined and emitted from the semiconductor laser device 100 in one optical path (for example, the optical axes of the plurality of laser lights are aligned). NS.

The semiconductor laser device 100 includes a plurality of semiconductor laser arrays 200, 201, 202, a collimator optical system (collimator lens) 260, 261, 262, a combiner (wavelength dispersion element) 270, and an external resonator (half mirror). 280 and.

Each of the plurality of semiconductor laser arrays 200, 201, and 202 is a semiconductor laser light source that emits a plurality of light (laser light). Each of the plurality of semiconductor laser arrays 200, 201, 202 has one light emitting point, that is, includes a plurality of semiconductor laser elements that emit one laser beam. Each of the plurality of semiconductor laser arrays 200, 201, and 202 is a semiconductor laser array in which such a plurality of semiconductor laser elements are integrally formed.

The collimator optical systems 260, 261, and 262 are collimator lenses that collimate the laser light emitted from the semiconductor laser array, respectively. The collimator optical systems 260, 261, and 262 each include, for example, a fast-axis collimator lens (FAC / Fast Axis Collimator) and a slow-axis collimator lens (SAC / Slow Axis Collimator), respectively.

The combiner 270 is an optical system that combines and emits laser light emitted from each of the semiconductor laser arrays 200, 201, and 202. In this embodiment, the combiner 270 has a wavelength dispersion element.

The wavelength dispersion element is an optical system having a diffraction grating. The wavelength dispersion element reflects light at an angle corresponding to the wavelength of the incident light. Therefore, according to the wavelength dispersion element, a plurality of laser beams having different wavelengths can be emitted as one laser beam. Further, according to the wavelength dispersion element, one laser beam including light having a plurality of wavelengths can be emitted at different angles for each wavelength.

In the present embodiment, the reflection type wavelength dispersion element is illustrated, but a transmission type wavelength dispersion element may also be used.

The external cavity 280 is a half mirror that transmits a part of the incident laser beam and reflects the other part. The laser light reflected by the external resonator 280 returns to the semiconductor laser arrays 200, 201, 202 via the combiner 270 and the collimator optical system 260. The laser light returned to the semiconductor laser arrays 200, 201, 202 passes through the inside of the semiconductor laser arrays 200, 201, 202 (more specifically, the waveguide) and is reflected by the semiconductor laser arrays 200, 201, 202. It is reflected by the surface (the surface opposite to the exit end surface that emits the laser beam). The reflected laser light passes through the inside of the semiconductor laser arrays 200, 201, 202 (more specifically, the waveguide) and is emitted from the emission end faces of the semiconductor laser arrays 200, 201, 202.

In this way, the laser light resonated between the reflecting surfaces of the semiconductor laser arrays 200, 201, 202 and the external resonator 280 is emitted from the semiconductor laser apparatus 100.

[Structure of semiconductor laser element]
Subsequently, the configuration of the semiconductor laser device according to the embodiment will be described with reference to FIGS. 2 to 4. Since the structures of the semiconductor laser arrays 200, 201, and 202 included in the semiconductor laser apparatus 100 are substantially the same except for the stripe width described later, the structure of the semiconductor laser array 200 will be described in detail.

The semiconductor laser device 100 includes a plurality of semiconductor laser elements in which a first conductive type semiconductor layer, an active layer, and a second conductive type semiconductor layer different from the first conductive type are laminated in this order. In the present embodiment, the plurality of semiconductor laser elements included in the semiconductor laser device 100 include a semiconductor laser element (first semiconductor laser element) 10, a semiconductor laser element (second semiconductor laser element) 11, and a semiconductor laser element (first semiconductor laser element). 3 Semiconductor laser element) 12 and the like. Further, in the present embodiment, the semiconductor laser device 100 includes a semiconductor laser array in which a plurality of semiconductor laser elements are integrally formed. Specifically, the semiconductor laser device 100 includes a semiconductor laser array 200 in which the semiconductor laser element 10, the semiconductor laser element 11, and the semiconductor laser element 12 are integrally formed. The number of semiconductor laser elements included in the semiconductor laser array 200 may be a plurality, and is not particularly limited.

FIG. 3 is a top view showing the semiconductor laser device according to the embodiment.

The plurality of semiconductor laser elements 10, 11 and 12 included in the semiconductor laser array 200 include a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer, and a ridge portion (striped structure), respectively. .. Specifically, the semiconductor laser device 10 includes a first conductive semiconductor layer, an active layer (first active layer) 103, a second conductive semiconductor layer, and a ridge portion (first stripe structure) 10R. Be prepared. Further, the semiconductor laser device 11 includes a first conductive type semiconductor layer, a second active layer 103a (see FIG. 4), a second conductive type semiconductor layer, and a ridge portion (second stripe structure) 11R. Further, the semiconductor laser device 12 includes a first conductive type semiconductor layer, a third active layer 103b (see FIG. 4), a second conductive type semiconductor layer, and a ridge portion 12R. In the present embodiment, the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer of the semiconductor laser devices 10, 11 and 12, respectively, are integrally formed (as one layer).

The ridge portions 10R, 11R, and 12R are narrowed portions formed in the semiconductor laser elements 10, 11, and 12 in order to narrow the current flowing through the active layer of the semiconductor laser elements 10, 11, 12, respectively. The ridge portions 10R, 11R, and 12R extend in the light emission direction (in the present embodiment, the Y-axis direction). Waveguides are formed below the ridges 10R, 11R, and 12R, and light is emitted from the emission end face 240 through the waveguide. The waveguide is a light waveguide formed by a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer.

Specifically, the semiconductor laser device 10 has a ridge portion 10R for narrowing the current flowing through the first active layer 103, and emits the first light (light 400). Further, the semiconductor laser element 11 has a ridge portion 11R for narrowing the current flowing through the second active layer 103a, and emits second light (light 401) having a wavelength different from that of the light 400. Further, the semiconductor laser device 12 has a ridge portion 12R for narrowing the current flowing through the third active layer 103b, and emits a third light (light 402) having a wavelength different from that of the lights 400 and 401.

The collimator optical system 260 collimates the lights 400, 401, and 402 emitted from the semiconductor laser elements 10, 11, and 12, respectively, and emits them to the combiner 270. Specifically, for example, the collimator optical system is a collimator lens that collimates light 400, 401, and 402 between the semiconductor laser element 10, the semiconductor laser element 11, and the semiconductor laser element 12 and the external resonator 280. Is. Further, in the present embodiment, the first end surface of the semiconductor laser element 10 that emits the light 400, the second end surface of the semiconductor laser element 11 that emits the light 401, and the third end surface that emits the light 402 of the semiconductor laser element 12 are emitted. The end face is the same end face (emission end face 240). In the present embodiment, the distance between the first end surface and the collimator optical system 260, the distance between the second end surface and the collimator optical system 260, and the distance between the third end surface and the collimator optical system 260 are equal to each other at a distance L10. be. Further, the collimator optical system 260 collects the incident light (feedback light) reflected by the external resonator 280 and demultiplexed by the combiner 270 into the semiconductor laser elements 10, 11 and 12, respectively. And exit.

In the present embodiment, the collimator optical system 260 includes a lens unit that collimates the light 400 emitted from the semiconductor laser element 10, a lens unit that collimates the light 401 emitted from the semiconductor laser element 11, and the semiconductor laser element 12. The lens portion that collimates the light 402 emitted from the light 402 is integrally formed, but it may be formed separately. In the present embodiment, each lens portion is made of the same material and has the same shape (for example, the lens surface has the same curvature).

The combiner 270 combines the lights 400, 401, and 402 emitted from the collimator optical system 260 and emits them to the external resonator 280. In the present embodiment, the combiner 270 has a wavelength dispersion element having a diffraction grating that combines and emits light 400, 401, and 402. Further, the combiner 270 demultiplexes the incident light by being reflected by the external resonator 280 and emits it to the collimator optical system 260.

The external resonator 280 resonates the light 400 with the semiconductor laser element 10 via the combiner 270, resonates the light 401 with the semiconductor laser element 11 via the combiner 270, and The light 402 is resonated with the semiconductor laser element 12 via the combiner 270. In the present embodiment, the external resonator 280 is a half mirror that transmits a part of each of the light 400, 401, and 402 and reflects the other part.

Further, the light reflected by the external resonator 280 shown in FIG. 2 is incident from the exit end face 240, waveguideed through the waveguide, reflected by the reflection end face 250, and further waveguideed through the waveguide. It is emitted from the emission end face 240. For example, light having different wavelengths is incident and emitted from the semiconductor laser element 10, the semiconductor laser element 11, and the semiconductor laser element 12. Specifically, the light 400 incident and emitted by the semiconductor laser element 10, the light 401 incident and emitted by the semiconductor laser element 11, and the light 402 incident and emitted by the semiconductor laser element 12 have different wavelengths. different.

Therefore, when the same collimeter optical system 260 is used and the distance between the collimeter optical system 260 and the emission end face 240 is the same, the semiconductor laser element 10, the semiconductor laser element 11, and the semiconductor laser element 12 have an emission end surface. At 240, the spot diameters of the light 400, the light 401, and the light 402 are different.

Further, the ridge portion 10R, the ridge portion 11R, and the ridge portion 12R have different widths (length in the X-axis direction in the present embodiment). For example, the widths of the ridge portions 10R, 11R, and 12R are sized according to the spot diameters of the emission end faces 240 of the light 400, 401, and 402, respectively. Specifically, when viewed from the stacking direction (in the present embodiment, when the semiconductor laser array 200 is viewed from the Z-axis positive direction side), the light 400 of the semiconductor laser element 10 is emitted from the first end surface. The stripe width (width L0), which is the width of the ridge portion 10R, the second stripe width (width L1), which is the width of the ridge portion 11R at the second end surface of the semiconductor laser element 11 that emits light 401, and the semiconductor laser element. The width of the third stripe (width L2), which is the width of the ridge portion 12R at the end face that emits the light 402 in No. 12, is different from each other. In the present embodiment, the width here is the length in the X-axis direction.

Further, the width of the ridge portions 10R, 11R, 12R in the semiconductor laser elements 10, 11 and 12 included in the semiconductor laser array 200 is smaller when the emitted wavelength is shorter. In this embodiment, the light 401 has a longer wavelength than the light 400. Further, the light 402 has a longer wavelength than the light 401. In the present embodiment, for example, the wavelengths of the light 400 and the light 401 are separated by about 0.1 to 0.3 nm. The wavelengths of the light 401 and the light 402 are separated by about 0.1 to 0.3 nm. The difference in wavelength between the light 400, the light 401, and the light 402 is not particularly limited.

Further, when viewed from the stacking direction, the width L0 at the exit end face 240 is smaller than the width L1 at the exit end face 240. Further, when viewed from the stacking direction, the width L1 at the exit end face 240 is smaller than the width L2 at the exit end face 240.

In the present embodiment, when viewed from the stacking direction, the ridge portions 10R, 11R, and 12R are the emission directions of the light 400, 401, and 402 of the semiconductor laser elements 10, 11, and 12, respectively (this embodiment). In the form of, the widths L0, L1 and L2 extend uniformly in the Y-axis direction). For example, the ridge portion R10 extends uniformly with a width L0 in the emission direction of the light 400 in the semiconductor laser element 10. Further, for example, the ridge portion 11R extends uniformly with a width L1 in the emission direction of the light 401 in the semiconductor laser element 11. Further, for example, the ridge portion 12R extends uniformly with a width L2 in the emission direction of the light 402 in the semiconductor laser element 12.

FIG. 4 is a cross-sectional view showing a semiconductor laser device according to the embodiment. Specifically, FIG. 4 shows a cross section of the semiconductor laser device array 200 having a plurality of semiconductor laser devices according to the embodiment in the IV-IV line of FIG. The semiconductor laser elements 10, 11 and 12 have waveguides 10L, 11L and 12L, respectively, and have the same layer structure except for the widths L0, L1 and L2 of the ridge portions 10R, 11R and 12R. Therefore, the structure of the semiconductor laser device 10 will be described in detail below.

The semiconductor laser element 10 is a laser element having a light emitting side end face (exiting end face 240 shown in FIG. 3) and a light reflecting side end face (reflecting end face 250 shown in FIG. 3) forming a resonator.

The semiconductor laser element 10 includes a substrate 101, a laminated structure, a second conductive side electrode 107, a pad electrode 108, and a first conductive side electrode 109. The laminated structure includes a first conductive clad layer 102 which is a first conductive semiconductor layer, an active layer (first active layer) 103, and a second conductive clad layer 104 which is a second conductive semiconductor layer. include. In the present embodiment, the laminated structure further includes a contact layer 105 and an insulating layer 106. A waveguide 10L is formed between one end face of the laminated structure and the other end face. A light emitting side end face coating film (not shown) is arranged on one end face (for example, emitting end face 240) of the laminated structure, and a light reflecting side end face coating is arranged on the other end face (for example, reflecting end face 250). A membrane (not shown) is placed.

As a result, the end face on one side of the laminated structure becomes the end face on the light emitting side, and the end face on the other side becomes the end face on the light reflecting side.

The substrate 101 is a base material of the semiconductor laser device 10. In this embodiment, the substrate 101 is a GaN single crystal substrate. The substrate 101 is not limited to a GaN single crystal substrate, and may be any substrate on which a nitride semiconductor layer can be laminated. For example, the substrate 101 may be a SiC substrate, a sapphire substrate, or the like.

The first conductive clad layer 102 is a clad layer made of a first conductive semiconductor arranged above the substrate 101. In the present embodiment, the first conductive clad layer 102 is an n-type Al _x Ga _1-x N (x = 0.03) layer doped with Si and having a film thickness of 3 μm. For example, the Si concentration in the first conductive clad layer 102 is 1 × 10 ¹⁷ cm ^-3 .

The active layer 103 is a light emitting layer arranged above the first conductive clad layer 102 and made of a nitride semiconductor containing In. In the present embodiment, the active layer 103 has a film thickness of 5 nm and has a _{well layer made of In x} Ga _1-x N, and a barrier layer having a film thickness of 10 nm and made of GaN alternately. Includes quantum well active layers stacked layer by layer.

The configuration of the active layer 103 is not limited to this. The active layer 103 may include a guide layer formed on at least one of the upper side and the lower side of the quantum well active layer.

The second conductive clad layer 104 is a clad layer arranged above the active layer 103 and made of a second conductive nitride semiconductor. In the present embodiment, the second conductive clad layer 104 includes a p-type AlGaN / GaN superlattice layer doped with Mg. For example, the Mg concentration in the second conductive clad layer 104 is 1 × 10 ¹⁹ cm ^-3 . Further, for example, in the AlGaN / GaN superlattice layer, the average composition ratio of Al is 3%, and 100 layers of AlGaN layers having a film thickness of 3 nm and GaN layers having a film thickness of 3 nm are alternately laminated. It is a layer.

The contact layer 105 is arranged above the second conductive clad layer 104 and is a layer made of a second conductive nitride semiconductor. In the present embodiment, the contact layer 105 is a GaN layer doped with Mg and having a film thickness of 5 nm. For example, the Mg concentration in the contact layer 105 is 1 × 10 ²⁰ cm ^-3 .

For example, the first conductive type is an n type, and the second conductive type is a p type. Of course, the first conductive type may be the p type, and the second conductive type may be the n type.

The insulating layer 106 is a layer made of an insulating material arranged above the second conductive clad layer 104. _{In the present embodiment, the insulating layer 106 is a layer made of SiO 2} having a film thickness of 200 nm and arranged on the side surface of the contact layer 105 and the upper surface of the second conductive clad layer 104.

The second conductive side electrode 107 is a layer made of a conductive material arranged above the contact layer 105. The second conductive side electrode 107 comes into contact with the contact layer 105. In the present embodiment, the second conductive side electrode 107 is a laminated film in which Pd and Pt are laminated in order from the contact layer 105 side.

The configuration of the second conductive side electrode 107 is not limited to this. The second conductive side electrode 107 may be, for example, a monolayer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt and Au. In the present embodiment, the width of the second conductive side electrode 107 is 30 μm. Here, the width of the second conductive side electrode 107 is parallel to the main surface (the surface on the Z-axis positive direction side) of the substrate 101 and is perpendicular to the resonance direction of the semiconductor laser element 10. Means the dimensions of.

The width of the second conductive side electrode 107 is not limited to 30 μm, and may be 10 μm or more and 150 μm or less. Further, the second conductive side electrode 107 may also be formed on the insulating layer 106.

The pad electrode 108 is a pad-shaped electrode arranged above the second conductive side electrode 107. In the present embodiment, the pad electrode 108 is a laminated film in which Ti and Au are laminated in order from the second conductive side electrode 107 side.

The configuration of the pad electrode 108 is not limited to this. The pad electrode 108 may be, for example, a laminated film of Ti and Au, Ti, Pt and Au, Ni and Au and the like.

The first conductive side electrode 109 is an electrode arranged below the substrate 101. In the present embodiment, the first conductive side electrode 109 is a laminated film in which Ti, Pt, and Au are laminated in this order from the substrate 101 side.

The configuration of the first conductive side electrode 109 is not limited to this. The first conductive side electrode 109 may be, for example, a laminated film of Ti and Au, Ti, Pt, Au and the like.

Further, the semiconductor laser element 10 has a ridge portion 10R and a waveguide 10L.

The ridge portion 10R is a narrowed portion formed in the semiconductor laser element 10 in order to narrow the current flowing through the active layer 103. The ridge portion 10R is, for example, a part of the second conductive clad layer 104. The ridge portion 10R extends in the Y-axis direction.

The waveguide 10L is a portion through which light is guided inside the semiconductor laser device 10. The waveguide 10L is composed of, for example, a part of the first conductive clad layer 102, a part of the active layer 103, and a part of the second conductive clad layer 104. The position where light is generated in the active layer 103 is determined by narrowing the current flowing through the active layer 103 by the ridge portion 10R. Therefore, when viewed in cross section (for example, when the cross section of FIG. 4 is viewed), for example, the width of the ridge portion 10R (length in the Y-axis direction) is the width of 10 L of the waveguide (length in the Y-axis direction). Is almost the same as. Further, the width of the light emitting point of the light 400 emitted from the semiconductor laser element 10 (the light emitting portion in the emitting end surface 240) in the X-axis direction is the width of the waveguide 10L in the X-axis direction and the width L0 of the ridge portion 10R. And it will be about the same.

As described above, the structures of the semiconductor laser arrays 201 and 202 included in the semiconductor laser apparatus 100 are substantially the same as those of the semiconductor laser array 200 except for the stripe width. For example, the semiconductor laser array 201 includes a plurality of ridge portions having different stripe widths from the plurality of ridge portions included in the semiconductor laser array 200, and having different stripe widths from each other. Further, for example, the semiconductor laser array 202 includes a plurality of ridge portions having different stripe widths from the plurality of ridge portions included in the semiconductor laser arrays 200 and 201, and having different stripe widths from each other.

[Study results]
FIG. 5 is a graph showing an oscillation threshold current density with respect to an oscillation wavelength in the semiconductor laser device according to the embodiment. Note that FIG. 5 shows the calculation result (shown by the broken line) and the experimental result (shown by ◯). In the graph shown in FIG. 5, the horizontal axis is the wavelength (oscillation wavelength) of the laser light emitted from the semiconductor laser element, and the vertical axis is the stacking direction for oscillating the laser light of the corresponding wavelength in the semiconductor laser element. It is a threshold value (oscillation threshold current density) of the current density per unit area of the ridge portion when viewed from the viewpoint. The calculation results and experimental results in FIG. 5 are the results when InGaN is used for the active layer and the resonator length is 2 mm. Further, in the calculation for obtaining the calculation result shown in FIG. 5, the band calculation using the physical property parameters described in Non-Patent Document 1 and the k · p perturbation described in Non-Patent Document 2 is described in Non-Patent Document 3. It is applied to the classical laser theory described.

As shown in FIG. 5, in both the experimental result and the calculation result, the oscillation threshold current density per unit area decreases as the oscillation wavelength becomes longer up to about 450 nm.

For example, in the configuration disclosed in Patent Document 1 described above, a process including a DDL type semiconductor laser device that emits a wavelength in the 400 nm band (for example, 400 nm to 450 nm) by a wavelength synthesis method using the wavelength dispersion element described above. When constructing a machine system, the semiconductor laser device needs to have a large number of emitters that oscillate in the 400 nm band, for example.

For a semiconductor laser device that emits laser light in the 400 nm band, for example, an InGaN-based semiconductor is used for the active layer.

In the InGaN-based semiconductor, the oscillation wavelength can be lengthened by increasing the In composition. On the other hand, by increasing the In composition, the oscillation threshold current density decreases due to a change in the band structure of the semiconductor or the like. Therefore, since the oscillation threshold current density is different for each of the plurality of semiconductor laser elements, there is a problem that the amount of current (oscillation threshold) to be input is different for each of the plurality of semiconductor laser elements per unit area.

Here, if the amount of current introduced into the active layer can be increased, the oscillation threshold value can be increased accordingly. For example, when viewed from the stacking direction, the amount of current introduced into the active layer can be increased by increasing the area of the ridge portion. On the other hand, for example, when viewed from the stacking direction, the amount of current introduced into the active layer can be reduced by reducing the area of the ridge portion. That is, by appropriately setting the size of each ridge portion of the plurality of semiconductor laser elements, the oscillation threshold values of the plurality of semiconductor laser elements can be made uniform.

FIG. 6 is a graph showing the stripe width (for example, the width of the ridge portion) with respect to the oscillation wavelength in the semiconductor laser device according to the embodiment. In the graph shown in FIG. 6, the horizontal axis represents the oscillation wavelength, and the vertical axis represents the luminous efficiency when the laser diode of the corresponding wavelength is emitted to the semiconductor laser element (for example, the luminous efficiency is 85% or more). A suitable stripe width. Further, FIG. 6 is a graph when the stripe width extends uniformly. Further, in FIG. 6, the resonator length (for example, the length of the semiconductor laser element 10 shown in FIG. 3 in the Y-axis direction) is constant.

As shown in FIG. 6, as the oscillation wavelength becomes longer, the suitable stripe width also increases.

Therefore, for example, even if the resonator length is the same, the longer the oscillation wavelength is, the wider the ridge width is, so that the coupling efficiency between the light incident on the semiconductor laser device and the waveguide can be increased.

From the above results, for example, by adjusting the size of the ridge portion when viewed from the stacking direction, it is possible to realize a semiconductor laser device in which the oscillation thresholds of the semiconductor laser elements are aligned and the coupling efficiency is good. ..

[Production method]
Subsequently, an outline of the method for manufacturing the semiconductor laser device according to the embodiment will be described with reference to the drawings.

7A to 7F are cross-sectional views showing each step of the method for manufacturing a semiconductor laser device according to the embodiment, respectively. 7A to 7F show enlarged views of the semiconductor laser device 10 in the cross section corresponding to FIG. 4.

First, as shown in FIG. 7A, the substrate 101 is prepared, and the first conductive clad layer 102, the active layer 103, the second conductive clad layer 104, and the contact layer 105 are placed on the substrate 101 in this order from the substrate 101 side. To form. In the present embodiment, each layer is formed by the organic metal vapor deposition method (MOCVD / Metal Oxide Chemical Vapor Deposition).

Next, as shown in FIG. 7B, a mask 110 made of _{SiO 2 or the like is formed on the contact layer 105.} In the present embodiment, a mask 110 having a film thickness of about 300 nm is formed by plasma CVD (Chemical Vapor Deposition).

Next, the mask 110 is patterned as shown in FIG. 7C. In this embodiment, a part of the mask 110 is selectively removed by using photolithography and etching. As a result, the band-shaped mask 110 is formed.

Next, as shown in FIG. 7D, the contact layer 105 and the second conductive clad layer 104 are etched by using the mask 110 formed in a band shape to obtain the contact layer 105 and the second conductive clad layer 104. A ridge portion 10R is formed on the surface. As the etching of the contact layer 105 and the second conductive clad layer 104, for example, dry etching by a reactive ion etching (RIE) method using a chlorine-based gas such as _{Cl 2 may be used.} Further, the mask 110 is removed by wet etching with hydrofluoric acid or the like.

Next, as shown in FIG. 7E, the insulating layer 106 is formed so as to cover the contact layer 105 and the second conductive clad layer 104. As the insulating layer 106, SiO ₂ having a film thickness of 300 nm is formed by plasma CVD.

Next, only the insulating layer 106 on the ridge portion 10R is removed by photolithography and wet etching to expose the upper surface of the contact layer 105.

Next, the second conductive side electrode 107 is formed on the contact layer 105 by using the vacuum deposition method and the lift-off method.

Next, the pad electrode 108 is formed so as to cover the second conductive side electrode 107 and the insulating layer 106. Specifically, a resist is patterned on a portion where the pad electrode 108 is not formed by photolithography or the like, a pad electrode 108 is formed on the entire upper surface of the substrate 101 by a vacuum vapor deposition method or the like, and an unnecessary portion is used by a lift-off method. To remove. As a result, the pad electrode 108 having a predetermined shape is formed.

By the above steps, the semiconductor laser device 10 is formed as shown in FIG. 7F.

[Effects, etc.]
As described above, the semiconductor laser device 100 according to the embodiment is a semiconductor laser device including a plurality of semiconductor laser elements in which a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are laminated in this order. Is. The plurality of semiconductor laser elements included in the semiconductor laser device 100 have a first stripe structure (for example, a ridge portion 10R) for narrowing the current flowing through the first active layer 103, and the semiconductor laser element 10 that emits light 400. And a semiconductor laser element 11 having a second stripe structure (for example, a ridge portion 11R) for narrowing the current flowing through the second active layer 103a and emitting light 401 having a wavelength longer than that of light 400. .. Further, the semiconductor laser device 100 includes an external resonator 280 that resonates the light 400 with the semiconductor laser element 10 and resonates the light 401 with the semiconductor laser element 11. When viewed from the stacking direction, the width of the first stripe structure (for example, width L0) at the first end surface (emission end surface 240) of the semiconductor laser element 10 that emits light 400 is the width of the semiconductor laser. It is smaller than the width of the second stripe (for example, the width L1), which is the width of the second stripe structure on the second end surface (emission end surface 240) that emits the light 401 in the element 11.

In this way, for example, among a plurality of semiconductor laser elements that emit light having different wavelengths, the stripe width of the semiconductor laser element that emits light on the long wavelength side is widened, and the semiconductor laser that emits light on the short wavelength side is widened. Narrow the stripe width of the element. For example, among the semiconductor laser elements 10 and 11, the width L1 of the ridge portion 11R of the semiconductor laser element 11 is made wider than the width L0 of the ridge portion 10R of the semiconductor laser element 10. This makes it possible to raise the oscillation threshold value in a semiconductor laser device having a long wavelength of emitted light. Alternatively, the oscillation threshold value can be lowered in a semiconductor laser device having a short wavelength of emitted light. Therefore, the oscillation thresholds of a plurality of semiconductor laser devices that emit light having different wavelengths can be brought close to each other. Further, according to such a configuration, for example, the waveguide in the first end surface of the semiconductor laser element 11 having a wide spot diameter of the light (return light) returning from the external resonator 280 is in the second end surface of the semiconductor laser element 10. Wider than the waveguide. Therefore, the coupling efficiency between the feedback light and the waveguide can be increased in any of the semiconductor laser devices 10 and 11. As described above, according to the semiconductor laser device 100, in an external resonator type semiconductor laser device including a plurality of semiconductor laser elements, the oscillation thresholds of the plurality of semiconductor laser elements can be brought close to each other. Further, according to the semiconductor laser device 100, since the coupling efficiency between the feedback light and the waveguide can be increased in any of the semiconductor laser elements 10 and 11, the optical output with respect to the input power, that is, the luminous efficiency can be increased.

Further, for example, when viewed from the stacking direction, the ridge portion 10R extends uniformly with a width L0 in the emission direction of the light 400 in the semiconductor laser element 10, and the ridge portion 11R is in the semiconductor laser element 11. It extends uniformly with a width L1 in the emission direction of the light 401.

According to this, the semiconductor laser elements 10 and 11 can be easily manufactured as compared with the case where the widths of the ridge portions 10R and 11R are partially changed.

Further, for example, the semiconductor laser array 200 in which the semiconductor laser element 10 and the semiconductor laser element 11 are integrally formed is provided.

According to this, for example, as compared with the case where the semiconductor laser element 10 and the semiconductor laser element 11 are separate bodies, the semiconductor laser element 10 and the semiconductor laser element 11 and the semiconductor laser device 100 such as the external resonator 280 are provided. Easy to align with the optical system.

Further, for example, the external resonator 280 includes a half mirror that transmits a part of each of the light 400 and the light 401 and reflects the other part.

According to this, external resonance can occur between the semiconductor laser elements 10 and 11 and the external resonator 280 with a simple configuration.

Further, for example, the semiconductor laser device 100 further includes a combiner 270 that combines and emits light 400 and light 401. That is, the combiner 270 combines the light 400 and the light 401 so that the optical axis of the light 400 and the optical axis of the light 401 pass on the same optical axis.

According to this, the light 400 and the light 401 can be irradiated to the same place by the combiner 270.

Further, for example, the combiner 270 has a wavelength dispersion element having a diffraction grating.

According to the combined wave using the wavelength dispersion element, light having a different wavelength is incident on the semiconductor laser element depending on the position. That is, the wavelengths of the light emitted by the plurality of semiconductor laser elements are different from each other. As described above, according to the semiconductor laser device 100, the oscillation thresholds of the plurality of semiconductor laser elements that emit light having different wavelengths can be brought close to each other, and the coupling efficiency between the feedback light and the waveguide can be brought close to each other. Can be increased in any of the semiconductor laser elements 10 and 11, so that the light output with respect to the input power, that is, the light emission efficiency can be increased. Therefore, the present invention is particularly useful for an external resonator type semiconductor laser device 100 that uses a combined wave by a wavelength dispersion element.

Further, for example, the semiconductor laser device 100 further includes a collimator lens (collimator optical system 260) that collimates the light 400 and the light 401 between the semiconductor laser element 10 and the semiconductor laser element 11 and the external resonator 280. ..

According to this, the semiconductor laser apparatus 100 can emit collimated light.

Further, for example, the distance between the first end surface and the collimator lens described above is equal to the distance between the second end surface and the collimator lens described above. In the present embodiment, the first end face and the second end face are both emission end faces 240, and the distance to the collimator lens is a distance L10.

In this way, for example, the semiconductor laser elements 10 and 11 are arranged so that the lights 400 and 401 are collimated using the same collimator lens and the distance from the collimator lens is the same. Compared with the case where the arrangement of the elements 10 and 11 is changed, the manufacturing becomes easier. Here, for example, the wavelengths of the light 400 are arranged by collimating the lights 400 and 401 using the same collimator lens and arranging the semiconductor laser elements 10 and 11 so that the distances from the collimator lenses are the same. The spot diameter of the feedback light on the exit end face 240 is different between the light 400 and the light 401 because the wavelength of the light 401 is different from that of the light 401. However, as described above, according to the semiconductor laser apparatus 100, the coupling efficiency between the feedback light and the waveguide can be increased in any of the semiconductor laser elements 10 and 11. Therefore, according to the present invention, the semiconductor laser device 100 in which the semiconductor laser elements 10 and 11 are arranged so that the light 400 and 401 are collimated using the same collimator lens and the distance from the collimator lens is the same. Especially useful.

[Modification example]
Hereinafter, a modified example of the semiconductor laser device according to the present disclosure will be described. In the description of the semiconductor laser device according to the modified example, the same reference numerals may be given to the configurations substantially the same as those of the semiconductor laser device 100, and the description may be partially simplified or omitted. In the semiconductor laser device according to the modified example, the shape of the ridge portion of the semiconductor laser device is different from that of the semiconductor laser device 100, and the other parts are substantially the same.

FIG. 8 is a top view showing a semiconductor laser device according to a modified example. Although the cross section is not shown in FIG. 8, the ridge portion is shown with hatching for the sake of explanation.

The semiconductor laser device according to the modified example includes a plurality of semiconductor laser elements in which a first conductive type semiconductor layer, an active layer, and a second conductive type semiconductor layer different from the first conductive type are laminated in this order. For example, in the semiconductor laser device according to the modified example, the semiconductor laser element (first semiconductor laser element) 13, the semiconductor laser element (second semiconductor laser element) 14, and the semiconductor laser element (third semiconductor laser element) 15 are included. A semiconductor laser array 203 integrally formed is provided. The number of semiconductor laser elements included in the semiconductor laser array 203 may be a plurality, and is not particularly limited.

The plurality of semiconductor laser elements 13, 14, and 15 included in the semiconductor laser array 203 include a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer, and a ridge portion (striped structure), respectively. .. Specifically, the semiconductor laser device 13 includes a first conductive semiconductor layer, a first active layer 103, a second conductive semiconductor layer, and a ridge portion (first stripe structure) 13R. Further, the semiconductor laser device 14 includes a first conductive type semiconductor layer, a second active layer 103a, a second conductive type semiconductor layer, and a ridge portion (second stripe structure) 14R. Further, the semiconductor laser device 15 includes a first conductive type semiconductor layer, a third active layer 103b, a second conductive type semiconductor layer, and a ridge portion (third stripe structure) 15R.

In this modification, the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer of the semiconductor laser devices 13, 14, and 15, are integrally formed.

The ridge portions 13R, 14R, and 15R are narrowed portions formed in the semiconductor laser elements 13, 14, and 15 in order to narrow the current flowing through the active layer of the semiconductor laser elements 13, 14, 15, respectively. The ridge portions 13R, 14R, and 15R extend in the light emission direction (in the present modification, the Y-axis direction). Waveguides are formed below the ridges 13R, 14R, and 15R, and light is emitted from the emission end face 240 through the waveguide.

Specifically, the semiconductor laser device 13 has a ridge portion 13R for narrowing the current flowing through the first active layer 103, and emits the first light (light 403). Further, the semiconductor laser element 14 has a ridge portion 14R for narrowing the current flowing through the second active layer 103a, and emits second light (light 404) having a wavelength different from that of the light 403. Further, the semiconductor laser element 15 emits a third light (light 405) having a wavelength different from that of the lights 403 and 404.

Here, when viewed from the stacking direction, the ridge portion 13R is on the side opposite to the direction in which the light 403 of the semiconductor laser element 13 is emitted from the first end surface (emission end surface 240) (Y in the present embodiment). The width becomes narrower toward the negative axis side). Specifically, the width of the ridge portion 13R becomes narrower from the exit end surface 240 toward the reflection end surface 250 when viewed from the stacking direction.

For example, when viewed from the stacking direction, the first stripe width (width L3), which is the width of the ridge portion 13R at the emission end surface 240 that emits the light 403 in the semiconductor laser element 13, is determined based on FIG. NS. As a result, in the semiconductor laser device 13, the coupling efficiency between the waveguide and the feedback light can be improved. Further, the oscillation threshold value can be appropriately set by appropriately setting the width of the ridge portion 13R in the portion other than the emission end surface 240. As described above, for example, when viewed from the stacking direction, the oscillation threshold value can be reduced by reducing the area of the ridge portion 13R. Therefore, by narrowing the width of the semiconductor laser element 13 toward the side opposite to the direction in which the light 403 is emitted, the coupling efficiency between the waveguide and the feedback light is improved, and the plurality of semiconductor laser elements 13 and 14 are used. , 15 can be approached at each oscillation threshold value. Further, for example, when viewed from the stacking direction, the ridge portion 13R has a tapered shape in which the width gradually narrows toward the negative direction side of the Y axis. According to this, the loss of light in the waveguide can be reduced as compared with the case where the width is sharply narrowed.

As shown in FIG. 8, when viewed from the stacking direction, the ridge portion 13R has a portion whose width gradually narrows toward the negative direction side of the Y axis and a portion having a uniform width. Alternatively, the width may continue to gradually narrow toward the negative side of the Y-axis.

Further, the width of the ridge portion 14R becomes narrower from the emission end surface 240 toward the side opposite to the direction in which the light 404 of the semiconductor laser element 14 is emitted.

Further, the width of the ridge portion 15R becomes narrower from the emission end surface 240 toward the side opposite to the direction in which the light 405 of the semiconductor laser element 15 is emitted.

For example, the oscillation threshold value of the semiconductor laser device 10 shown in FIG. 3 is 225 mA. Further, for example, the oscillation threshold value of the semiconductor laser device 11 shown in FIG. 3 is 220 mA. The oscillation threshold value of the semiconductor laser device 12 shown in FIG. 3 is 218 mA. As described above, when the widths of the ridge portions 10R, 11R, and 12R are made uniform so as to increase the coupling efficiency between the feedback light and the waveguide, the oscillation thresholds are set to the semiconductor laser element 10 and the semiconductor laser element 11. And the semiconductor laser element 12.

Here, the oscillation threshold values of the semiconductor laser elements 13, 14 and 15 shown in FIG. 8 are all 218 mA.

As described above, as shown in FIG. 8, the structure is configured such that the width becomes narrower from the emission end surface 240 toward the side opposite to the direction in which the light 403, 404, 405 of the semiconductor laser elements 13, 14, 405 is emitted. As a result, the oscillation threshold values of the semiconductor laser elements 13, 14 and 15 can be brought close to each other.

Further, by changing the widths of the ridge portions 13R, 14R, and 15R at positions other than the emission end face 240, the oscillation threshold value can be controlled without affecting the coupling efficiency between the feedback light and the waveguide. ..

Of the ridge portions 13R, 14R, and 15R, only a part (for example, the ridge portion 13R of the semiconductor laser element 13 having the shortest emitted light wavelength among the semiconductor laser elements 13, 14, 15) is a semiconductor. The width of the laser element 13 becomes narrower toward the side opposite to the direction in which the light 40 is emitted, and the width of the other portion (for example, the ridge portions 14R and 15R) is one in the direction in which the light is emitted from the semiconductor laser element. It may be extended like this.

Further, for example, in the semiconductor laser elements 13, 14 and 15, the ridge portion 13R of the semiconductor laser element 13 having the shortest emitted light wavelength is on the side opposite to the direction in which the light 403 of the semiconductor laser element 13 is emitted. The width becomes narrower toward the direction, and the width of the ridge portion 15R of the semiconductor laser element 15 having the longest emitted light wavelength becomes wider toward the side opposite to the direction in which the light 405 of the semiconductor laser element 15 is emitted. The width of the ridge portion 14R may extend uniformly in the direction in which the light 404 of the semiconductor laser element 14 is emitted.

(Other embodiments)
The semiconductor laser device according to the present disclosure has been described above based on the embodiment, but the present disclosure is not limited to the above embodiment.

For example, in the above-described embodiment, the ridge portion is exemplified as the striped structure, but the striped structure is not limited to the above-mentioned ridge portion. The striped structure may be a structure that narrows the current flowing through the active layer, and may be formed as a barrier layer that narrows the current inside the semiconductor laser device, for example.

Further, for example, in the above-described embodiment, the semiconductor laser array in which a plurality of semiconductor laser elements are integrally formed has been described, but the plurality of semiconductor laser elements may be individually formed as separate bodies. In this case, for example, the positions of the light emitting end faces in the plurality of semiconductor laser elements may be different from each other, such as not being located on the same plane.

Further, for example, when the semiconductor laser apparatus includes a plurality of semiconductor laser arrays, the plurality of semiconductor laser elements in the semiconductor laser array having the plurality of semiconductor laser elements have the same stripe width and the plurality of semiconductor lasers. The stripe width may be different for each array.

Further, for example, in the above embodiment, the GaN-based semiconductor laser array is described as an example, but GaN capable of changing the wavelength of the light emitting region such as a GaAs-based semiconductor, an InP-based semiconductor, or a II-VI group semiconductor. A semiconductor laser device using a material other than the system may be used. Further, for example, as a plurality of semiconductor laser elements included in a semiconductor laser device, a semiconductor laser array using a GaN-based material and a semiconductor laser array using a GaAs-based material are set so that the oscillation threshold values are close to each other. , The stripe width may be different and then used in combination. As described above, the semiconductor laser device may include a plurality of semiconductor laser elements whose materials are different from each other and whose stripe widths are different from each other.

Further, for example, in the above embodiment, a wavelength dispersion element is exemplified as a combiner in order to combine a plurality of laser beams, but the combiner is not limited to the wavelength dispersion element. The combiner may be, for example, a prism. Alternatively, the combiner may be a VBG (Volume Bragg Grating).

A form obtained by applying various modifications to the above-described embodiment, and a form realized by arbitrarily combining the components and functions of the above-described embodiment without departing from the spirit of the present disclosure. Included in this disclosure.

The semiconductor laser apparatus of the present disclosure can be applied to a light source used for laser processing, particularly a light source of a laser processing machine using a semiconductor laser apparatus for direct processing.

10, 13 Semiconductor laser element (first semiconductor laser element)
10L, 11L, 12L, 1020, 1021, 1022 Waveguide 10R, 13R Ridge part (first stripe structure)
11, 14 Semiconductor laser element (second semiconductor laser element)
11R, 14R ridge part (second stripe structure)
12, 15 Semiconductor laser element (third semiconductor laser element)
12R, 15R ridge part (third stripe structure)
100 Semiconductor laser device 101 Substrate 102 First conductive clad layer 103 Active layer (first active layer)
103a 2nd active layer 103b 3rd active layer 104 2nd conductive clad layer 105 Contact layer 106 Insulation layer 107 2nd conductive side electrode 108 Pad electrode 109 1st conductive side electrode 200, 201, 202, 203, 1000 Semiconductor laser array 240 Ejecting end face 250 Reflecting end face 260, 261, 262, 1060 Collimator optical system (collimator lens)
270 combiner (wavelength disperser)
280 external cavity (half mirror)
400, 401, 402, 403, 404, 405, 1040, 1041, 1042 Optical 1010, 1011, 1012 Semiconductor laser element L0, L1, L2, L3, L4, L5 Width L10 Distance

Claims (9)

A semiconductor laser device including a plurality of semiconductor laser elements in which a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are laminated in this order.
The plurality of semiconductor laser elements
A first semiconductor laser device having a first stripe structure for narrowing the current flowing through the first active layer and emitting first light,
A second semiconductor laser device having a second stripe structure for narrowing the current flowing through the second active layer and emitting a second light having a wavelength longer than that of the first light is included.
The semiconductor laser device includes an external resonator that resonates the first light with the first semiconductor laser element and resonates the second light with the second semiconductor laser element.
When viewed from the stacking direction, the width of the first stripe structure, which is the width of the first stripe structure on the first end surface of the first semiconductor laser device that emits the first light, is the width of the first stripe structure of the second semiconductor laser device. A semiconductor laser device that is smaller than the width of the second stripe, which is the width of the second stripe structure on the second end surface that emits the second light. When viewed from the stacking direction
The first stripe structure extends uniformly in the emission direction of the first light in the first semiconductor laser device with the width of the first stripe.
The semiconductor laser device according to claim 1, wherein the second stripe structure uniformly extends in the emission direction of the second light in the second semiconductor laser element with the width of the second stripe. Claim that the width of the first stripe structure becomes narrower from the first end surface toward the side opposite to the direction in which the first light is emitted from the first semiconductor laser device when viewed from the stacking direction. The semiconductor laser device according to 1. The semiconductor laser apparatus according to any one of claims 1 to 3, further comprising a semiconductor laser array in which the first semiconductor laser element and the second semiconductor laser element are integrally formed. The semiconductor laser according to any one of claims 1 to 4, wherein the external resonator includes a half mirror that transmits a part of each of the first light and the second light and reflects the other part. Device. The semiconductor laser device according to any one of claims 1 to 5, further comprising a combiner that combines and emits the first light and the second light. The semiconductor laser device according to claim 6, wherein the combiner has a wavelength dispersion element having a diffraction grating. Further, any one of claims 1 to 7, further comprising a collimator lens that collimates the first light and the second light between the first semiconductor laser element and the second semiconductor laser element and the external resonator. The semiconductor laser device according to item 1. The semiconductor laser device according to claim 8, wherein the distance between the first end surface and the collimator lens and the distance between the second end surface and the collimator lens are equal.

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