JP7426255B2 - semiconductor laser equipment - Google Patents

Description

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

Conventionally, there is a semiconductor laser device used as a light source for laser processing. This type of semiconductor laser device is required to have high optical output. Therefore, in order to obtain high optical output, there is a method of combining a plurality of laser beams so that they pass through one optical path, that is, a method of multiplexing a plurality of laser beams (for example, see Patent Document 1).

In addition, conventionally, in order to improve optical output, external cavity type semiconductor lasers emit light as laser light by causing the light emitted by a semiconductor laser element to resonate between the semiconductor laser element and an optical system such as a half mirror. There is a device.

Here, in order to emit laser light from the semiconductor laser device by externally resonating the light between the plurality of semiconductor laser elements using an optical system such as a half mirror, a light beam is input to each of the plurality of semiconductor laser elements. The amount of current that needs to be applied may vary depending on the wavelength of light emitted by the plurality of semiconductor laser elements. This is because each of the plurality of semiconductor elements has a different oscillation threshold. In order to supply different amounts of current to each of the plurality of semiconductor laser elements, the structure becomes more complicated than when the same amount of current is supplied to each of the plurality of semiconductor laser elements.

Patent No. 5981855

J. Piprek and S. Nakamura, Physics of high-power InGaN=GaN lasers, IEE Proc. -Optoelectron. , Vol. 149, No. 4, August 2002 S. K. Pugh, D. J. Dugdale, S. 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 an external cavity type semiconductor laser device including a plurality of semiconductor laser elements, in which the oscillation thresholds of the plurality of semiconductor laser elements can be brought close to each other.

A semiconductor laser device according to one aspect of the present disclosure is a semiconductor laser device including a plurality of semiconductor laser elements in which a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer are stacked in this order. The semiconductor laser device has a first stripe structure for confining the current flowing through the first active layer, and constricts the current flowing through the first semiconductor laser device emitting the first light and the second active layer. a second semiconductor laser device having a second stripe structure for emitting second light having a longer wavelength than the first light; an external resonator for resonating the first light with the second semiconductor laser element and resonating the second light with the second semiconductor laser element; The first stripe width, 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 element. The second stripe width is smaller than the second stripe width.

According to the present disclosure, in an external cavity type semiconductor laser device including a plurality of semiconductor laser elements, it is possible to provide a semiconductor laser device in which the oscillation thresholds of the plurality of semiconductor laser elements can be brought close to each other.

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 taken along line IV-IV in FIG. 3, showing the semiconductor laser device according to the embodiment. FIG. 5 is a graph showing the oscillation threshold current density versus the oscillation wavelength in the semiconductor laser device according to the embodiment. FIG. 6 is a graph showing the stripe width versus 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 the second step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7C is a schematic cross-sectional view showing the third step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7D is a schematic cross-sectional view showing the fourth step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7E is a schematic cross-sectional view showing the fifth step of the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 7F is a schematic cross-sectional view showing the 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.

(Findings that formed the basis of this disclosure)
The semiconductor laser device according to the present disclosure is used, for example, as a light source for laser processing.

Laser processing is attracting attention as a means of welding, cutting, modifying, etc. with good controllability and cleanliness on materials to be processed, such as metals, resins, and carbon fibers. Laser machining can achieve high-quality machining because, for example, it is possible to perform small spot welding compared to arc discharge, and the generation of chips can be suppressed compared to cutting using a mold.

A laser processing machine that performs such laser processing may employ a DDL (Direct Diode Laser) method that directly uses laser light emitted from a semiconductor laser device.

The DDL method is (i) highly efficient because it does not convert the 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 characteristics: it can be processed with any laser beam. In recent years, in the DDL method, semiconductor laser devices equipped with semiconductor laser elements that use nitride semiconductors (GaN, InGaN, AlGaN, etc.) and emit laser light with a wavelength of 400 nm have gained popularity in that they 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), which is the light emitting part (active layer) of a semiconductor laser element, it is possible to increase the power that can be input to the light emitting part.

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

However, the luminous efficiency of semiconductor laser devices is between 30% and 50%. Electric power that does not contribute to light emission turns into heat and increases the temperature of the emitter. This temperature increase causes thermal saturation in the semiconductor laser device due to light emission, and has a negative effect on improving the output of the semiconductor laser device.

Therefore, there is a semiconductor laser array having an array structure (also referred to as 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 be irradiated onto the workpiece at one point. Therefore, for example, the optical axes of the plurality of laser beams need to be aligned.

For example, as a method of aligning a plurality of laser beams to one optical axis (in other words, combining them so that they pass through one optical path), there is a wavelength synthesis method. The wavelength synthesis method is a method of converging the optical axes of multiple laser beams emitted from a semiconductor laser array to the same optical axis, and the beam quality is high (for example, the optical spot of multiple laser beams on the material to be processed is It has the characteristic that the position and shape of the parts can be easily aligned.

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

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 beams incident on the diffraction grating is θi, (i=1, 2,..., N), and when m is any integer other than 0, the following formula (1) is satisfied.

d×(sinθi+sinθ0)=mλi Formula (1)

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

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

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

Note that 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. In addition, the comparative example described below is an external resonator type wavelength synthesis method in which external resonance is performed between the semiconductor laser array 1000 and an output coupler (an optical system such as a half mirror). 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, a semiconductor laser array 1000), and a collimator optical system (collimator lens) 1060 and a diffraction grating are arranged. A wavelength dispersion element (not shown) is disposed between the semiconductor laser array 1000 and the output coupler.

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

In Patent Document 1 mentioned above, an arsenide semiconductor (GaAs (Gallium Arsenide), AlGaAs (Aluminum Gallium Arsenide), InGaAs (Indium Gallium Arsenide), etc.) having a near-infrared wavelength is used, and a DDL method is adopted. wavelength synthesis A legal system is proposed. When multiplexing light from a large number of emitters as in the system disclosed in Patent Document 1, it is important to emit uniform and high-output light 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, through the optical system in the opposite direction to the semiconductor laser element. This returning light is focused by a collimator optical system and irradiated onto the end face of the semiconductor laser element.

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

For example, as shown in FIG. 1, light 1040 reflected by an output coupler is incident on a semiconductor laser device 1010. Furthermore, 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 due to, for example, a wavelength dispersion element. Here, as shown in FIG. 1, the spread width of the light at the end faces of the semiconductor laser elements 1010, 1011, 1012 differs depending on the wavelength of the light 1040, 1041, 1042. The proportion of light coupled to the waveguide mode in the waveguides 1030, 1031, and 1032 differs among the semiconductor laser elements 1010, 1011, and 1012.

Furthermore, even if the width of the light returning to a semiconductor laser device that oscillates at a certain wavelength is designed to increase the coupling efficiency to the waveguide mode, the coupling efficiency will be low for a semiconductor laser device that oscillates at a different wavelength. Since the appropriate width of the laser beam to be increased differs, the coupling efficiency cannot be increased.

As a result of intensive studies, the inventors of the present application have determined that by appropriately setting the size of the waveguide of a semiconductor laser device according to the wavelength of the emitted light, the coupling efficiency of the waveguide mode in the waveguide can be increased by the wavelength of the light. It has been found that it is possible to maintain a large size regardless of the Further, as a result of extensive studies, the inventors of the present invention have found that the oscillation threshold can be adjusted by appropriately setting the size of the stripe structure for confining the current applied to the semiconductor laser element.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that the embodiments described below each represent a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and do not limit the present disclosure.

Furthermore, each figure is a schematic diagram and is not necessarily strictly illustrated. Therefore, the scale etc. in each figure are not necessarily the same. In addition, in each figure, the same code|symbol is attached to the substantially the same structure, and the overlapping description is omitted or simplified.

Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upper direction (vertically upward) or the lower direction (vertically downward) in absolute spatial recognition, but are based on the stacking order in the stacked structure. Used as a term defined by the relative positional relationship. Additionally, the terms "above" and "below" are used not only when two components are spaced apart and there is another component between them; This also applies when they are placed in contact with each other.

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

Further, in this specification, the numerical values described for dimensions etc. do not only mean the exact 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 beam has a wavelength of, for example, about 400 nm to 450 nm, and a plurality of laser beams are combined and emitted from the semiconductor laser device 100 in one optical path (for example, the optical axes of the plurality of laser beams are aligned). Ru.

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

Each of the plurality of semiconductor laser arrays 200, 201, and 202 is a semiconductor laser light source that emits a plurality of lights (laser lights). Each of the plurality of semiconductor laser arrays 200, 201, and 202 has one light emitting point, that is, it 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 a plurality of such semiconductor laser elements are integrally formed.

Collimator optical systems 260, 261, and 262 are collimator lenses that collimate 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).

The multiplexer 270 is an optical system that multiplexes and outputs laser beams emitted from each of the semiconductor laser arrays 200, 201, and 202. In this embodiment, multiplexer 270 includes a wavelength dispersion element.

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

Note that in this embodiment, a reflection type wavelength dispersion element is illustrated, but a transmission type wavelength dispersion element may also be used.

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

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

[Structure of semiconductor laser device]
Next, the configuration of the semiconductor laser device according to the embodiment will be described with reference to FIGS. 2 to 4. Note that the structures of the semiconductor laser arrays 200, 201, and 202 included in the semiconductor laser device 100 are substantially the same except for the stripe width described later, so 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 conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer different from the first conductivity type are stacked in this order. In this 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 (second semiconductor laser element) 10, a semiconductor laser element (second semiconductor laser element) 11, and a semiconductor laser element (second semiconductor laser element) 11. 3 semiconductor laser element) 12. Further, in this 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 a semiconductor laser element 10, a semiconductor laser element 11, and a semiconductor laser element 12 are integrally formed. Note that the number of semiconductor laser elements included in the semiconductor laser array 200 is not particularly limited as long as it is plural.

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 each include a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, and a ridge portion (stripe structure). . Specifically, the semiconductor laser device 10 includes a first conductivity type semiconductor layer, an active layer (first active layer) 103, a second conductivity type semiconductor layer, and a ridge portion (first stripe structure) 10R. Be prepared. Further, the semiconductor laser element 11 includes a first conductivity type semiconductor layer, a second active layer 103a (see FIG. 4), a second conductivity type semiconductor layer, and a ridge portion (second stripe structure) 11R. Further, the semiconductor laser element 12 includes a first conductivity type semiconductor layer, a third active layer 103b (see FIG. 4), a second conductivity type semiconductor layer, and a ridge portion 12R. In this embodiment, the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer of each of the semiconductor laser elements 10, 11, and 12 are formed integrally (as one layer).

The ridge portions 10R, 11R, and 12R are constriction portions formed in the semiconductor laser devices 10, 11, and 12 to constrict the current flowing in the active layers of the semiconductor laser devices 10, 11, and 12, respectively. The ridge portions 10R, 11R, and 12R extend in the light emission direction (in this embodiment, the Y-axis direction). Waveguides are formed below the ridges 10R, 11R, and 12R, and light is guided through the waveguides and is emitted from the output end face 240. The waveguide is an optical waveguide formed by a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer.

Specifically, the semiconductor laser device 10 has a ridge portion 10R for confining 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 confining the current flowing through the second active layer 103a, and emits second light (light 401) having a different wavelength from the light 400. Further, the semiconductor laser element 12 has a ridge portion 12R for confining the current flowing through the third active layer 103b, and emits third light (light 402) having a different wavelength from 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 outputs the collimated lights to the multiplexer 270. Specifically, for example, the collimator optical system includes collimator lenses that collimate each of the lights 400, 401, and 402 between the semiconductor laser element 10, the semiconductor laser element 11, the semiconductor laser element 12, and the external resonator 280. It is. Further, in this embodiment, a first end facet of the semiconductor laser element 10 that emits the light 400, a second end facet of the semiconductor laser element 11 that emits the light 401, and a third end facet of the semiconductor laser element 12 that emits the light 402 are described. The end faces are the same end face (emission end face 240). In this 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 the distance L10. be. Further, the collimator optical system 260 focuses the incident light (return light) that is reflected by the external resonator 280 and demultiplexed by the multiplexer 270 onto each of the semiconductor laser elements 10, 11, and 12. and emit light.

In this embodiment, the collimator optical system 260 includes a lens section that collimates the light 400 emitted from the semiconductor laser device 10, a lens section that collimates the light 401 emitted from the semiconductor laser device 11, and a lens section that collimates the light 401 emitted from the semiconductor laser device 12. Although the lens portion that collimates the light 402 emitted from the lens portion is formed integrally with the lens portion, they may be formed separately. In this embodiment, each lens part is formed of the same material and the same shape (for example, the lens surface has the same curvature).

The multiplexer 270 multiplexes the lights 400 , 401 , and 402 emitted from the collimator optical system 260 and outputs the multiplexed lights to the external resonator 280 . In this embodiment, the multiplexer 270 includes a wavelength dispersion element having a diffraction grating that multiplexes and outputs the lights 400, 401, and 402. Further, the multiplexer 270 splits the incident light by being reflected by the external resonator 280 and outputs the split light to the collimator optical system 260 .

The external resonator 280 resonates the light 400 with the semiconductor laser device 10 via the multiplexer 270, resonates the light 401 with the semiconductor laser device 11 via the multiplexer 270, and, The light 402 is caused to resonate with the semiconductor laser element 12 via the multiplexer 270. In this embodiment, external resonator 280 is a half mirror that transmits a portion of each of the lights 400, 401, and 402 and reflects the other portion.

Furthermore, the light reflected by the external resonator 280 shown in FIG. The light is emitted from the emission end face 240. For example, light of different wavelengths enters and exits the semiconductor laser device 10, the semiconductor laser device 11, and the semiconductor laser device 12. Specifically, the wavelengths of light 400 entering and exiting the semiconductor laser device 10, light 401 entering and exiting the semiconductor laser device 11, and light 402 entering and exiting the semiconductor laser device 12 are different.

Therefore, when the same collimator optical system 260 is used and the distance between the collimator optical system 260 and the emission end facet 240 is the same, the emission end facets of the semiconductor laser element 10, the semiconductor laser element 11, and the semiconductor laser element 12 are the same. In 240, the spot diameters of light 400, light 401, and light 402 are different.

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

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

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

Note that in this embodiment, when viewed from the stacking direction, the ridge portions 10R, 11R, and 12R are in the emission direction of the light beams 400, 401, and 402 of the semiconductor laser elements 10, 11, and 12, respectively (this embodiment In the embodiment, the widths L0, L1, and L2 extend uniformly in the Y-axis direction. For example, the ridge portion R10 uniformly extends in the emission direction of the light 400 in the semiconductor laser element 10 with a width L0. Further, for example, the ridge portion 11R uniformly extends 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 uniformly extends 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 an embodiment. Specifically, FIG. 4 shows a cross section of a semiconductor laser element array 200 having a plurality of semiconductor laser elements according to the embodiment, taken along line IV-IV in FIG. 3. Note that 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 device 10 is a laser device having a light emitting side end face (emitting 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 device 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 conductivity type cladding layer 102 which is a first conductivity type semiconductor layer, an active layer (first active layer) 103, and a second conductivity type cladding layer 104 which is a second conductivity type semiconductor layer. include. In this embodiment, the stacked structure further includes a contact layer 105 and an insulating layer 106. A waveguide 10L is formed between one end face and the other end face of the laminated structure. A light-emitting side end-face coating film (not shown) is disposed on one end face (e.g., the emitting end face 240) of the laminated structure, and a light-reflecting end face coat is disposed on the other end face (e.g., the reflective end face 250). A membrane (not shown) is placed.

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

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

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

The active layer 103 is a light emitting layer disposed above the first conductivity type cladding layer 102 and made of a nitride semiconductor containing In. In this embodiment, the active layer 103 has two well layers each having a thickness of 5 nm and made of In _x Ga _1-x N and barrier layers having a thickness of 10 nm and made of GaN. It includes a quantum well active layer stacked layer by layer.

Note that the configuration of the active layer 103 is not limited to this. The active layer 103 may include a guide layer formed above or below the quantum well active layer.

The second conductivity type cladding layer 104 is a cladding layer disposed above the active layer 103 and made of a second conductivity type nitride semiconductor. In this embodiment, the second conductivity type cladding layer 104 includes a p-type AlGaN/GaN superlattice layer doped with Mg. For example, the Mg concentration in the second conductivity type cladding layer 104 is 1×10 ¹⁹ cm ⁻³ . For example, the AlGaN/GaN superlattice layer has an average Al composition ratio of 3%, and is made up of 100 AlGaN layers each having a thickness of 3 nm and 100 GaN layers each having a thickness of 3 nm. It is a layer.

The contact layer 105 is a layer disposed above the second conductivity type cladding layer 104 and made of a second conductivity type nitride semiconductor. In this embodiment, contact layer 105 is a GaN layer doped with Mg and having a thickness of 5 nm. For example, the Mg concentration in the contact layer 105 is 1×10 ²⁰ cm ⁻³ .

Note that, for example, the first conductivity type is n-type, and the second conductivity type is p-type. Of course, the first conductivity type may be the p-type and the second conductivity type may be the n-type.

The insulating layer 106 is a layer made of an insulating material disposed above the second conductivity type cladding layer 104. In this embodiment, the insulating layer 106 is a layer made of SiO ₂ and has a thickness of 200 nm, and is disposed on the side surface of the contact layer 105 and the upper surface of the second conductivity type cladding layer 104.

The second conductive side electrode 107 is a layer made of a conductive material disposed above the contact layer 105. The second conductive side electrode 107 contacts the contact layer 105. In this 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.

Note that 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 single layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au. In this embodiment, the width of the second conductive side electrode 107 is 30 μm. Here, the width of the second conductive side electrode 107 refers to the width of the second conductive side electrode 107 in a direction parallel to the main surface (the surface on the positive side of the Z axis) of the substrate 101 and perpendicular to the resonance direction of the semiconductor laser element 10. means the dimensions of

Note that the width of the second conductive side electrode 107 is not limited to 30 μm, but may be from 10 μm to 150 μm. 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 this 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.

Note that 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, or the like.

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

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

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

The ridge portion 10R is a constriction portion formed in the semiconductor laser device 10 to constrict the current flowing through the active layer 103. The ridge portion 10R is, for example, a part of the second conductivity type cladding 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 includes, for example, a part of the first conductivity type cladding layer 102, a part of the active layer 103, and a part of the second conductivity type cladding layer 104. The current flowing through the active layer 103 is constricted by the ridge portion 10R, thereby determining the position where light is generated in the active layer 103. Therefore, when viewed in cross section (for example, when looking at the cross section in FIG. 4), for example, the width (length in the Y-axis direction) of the ridge portion 10R is the width (length in the Y-axis direction) of the waveguide 10L. It is almost the same as. Furthermore, the width in the X-axis direction of the light emitting point of the light 400 emitted from the semiconductor laser element 10 (the light emitting portion on the emission end face 240) is the width in the X-axis direction of the waveguide 10L and the width L0 of the ridge portion 10R. It will be about the same.

Note that, as described above, the structure of the semiconductor laser arrays 201 and 202 included in the semiconductor laser device 100 is substantially the same as that 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 stripe widths different from the plurality of ridge portions included in the semiconductor laser array 200 and mutually different stripe widths. Further, for example, the semiconductor laser array 202 includes a plurality of ridge portions having stripe widths different 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 the oscillation threshold current density versus the oscillation wavelength in the semiconductor laser device according to the embodiment. Note that FIG. 5 shows calculation results (indicated by broken lines) and experimental results (indicated by circles). In the graph shown in FIG. 5, the horizontal axis is the wavelength of the laser light emitted from the semiconductor laser device (oscillation wavelength), and the vertical axis is the stacking direction for making the semiconductor laser device oscillate the laser light of the corresponding wavelength. This is the threshold value of current density per unit area of the ridge portion (oscillation threshold current density) when viewed from above. The calculation results and experimental results in FIG. 5 are both results when InGaN is used for the active layer and the resonator length is 2 mm. In addition, in the calculations to obtain the calculation results shown in FIG. This is carried out by applying the classical laser theory described above.

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

For example, in the configuration disclosed in Patent Document 1 mentioned above, processing is provided with 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 above-mentioned wavelength dispersion element. When constructing an optical system, the semiconductor laser device needs to have a large number of emitters that oscillate in the 400 nm band, for example.

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

In an InGaN-based semiconductor, the oscillation wavelength can be made longer by increasing the In composition. On the other hand, by increasing the In composition, the oscillation threshold current density decreases due to changes in the band structure of the semiconductor. Therefore, since the oscillation threshold current density differs for each of the plurality of semiconductor laser elements, there is a problem that the amount of current (oscillation threshold) that should be applied to each of the plurality of semiconductor laser elements per unit area differs.

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

FIG. 6 is a graph showing the stripe width (for example, the width of the ridge portion) versus the oscillation wavelength in the semiconductor laser device according to the embodiment. In the graph shown in FIG. 6, the horizontal axis is the oscillation wavelength, and the vertical axis is the oscillation wavelength when the laser beam of the corresponding wavelength is emitted from the semiconductor laser element. ) is the preferred stripe width. Moreover, FIG. 6 is a graph when the stripe width extends uniformly. Further, in FIG. 6, the resonator length (for example, the length in the Y-axis direction of the semiconductor laser device 10 shown in FIG. 3) is constant.

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

Therefore, for example, if the resonator length is the same, the longer the oscillation wavelength is, the wider the ridge width can increase the coupling efficiency between the light incident on the semiconductor laser element and the waveguide.

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

[Production method]
Next, an outline of a method for manufacturing a semiconductor laser device according to an embodiment will be explained using 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. Note that FIGS. 7A to 7F show enlarged views of the semiconductor laser device 10 in a cross section corresponding to FIG. 4.

First, as shown in FIG. 7A, a substrate 101 is prepared, and a first conductivity type cladding layer 102, an active layer 103, a second conductivity type cladding layer 104, and a contact layer 105 are placed on the substrate 101 in order from the substrate 101 side. form. In this embodiment, each layer is formed by metal organic chemical vapor deposition (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 this embodiment, the mask 110 with a thickness of about 300 nm is formed by plasma CVD (Chemical Vapor Deposition).

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

Next, as shown in FIG. 7D, the contact layer 105 and the second conductive type cladding layer 104 are etched using the mask 110 formed in a band shape. A ridge portion 10R is formed on. For etching the contact layer 105 and the second conductivity type cladding layer 104, it is preferable to use, for example, dry etching using a reactive ion etching (RIE) method using a chlorine-based gas such as Cl ₂ . Further, the mask 110 is removed by wet etching using hydrofluoric acid or the like.

Next, as shown in FIG. 7E, an insulating layer 106 is formed to cover the contact layer 105 and the second conductivity type cladding layer 104. As the insulating layer 106, SiO ₂ with a thickness of 300 nm is formed by plasma CVD.

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

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

Next, a pad electrode 108 is formed to cover the second conductive side electrode 107 and the insulating layer 106. Specifically, a resist is patterned by photolithography or the like in the areas where the pad electrodes 108 are not to be formed, the pad electrodes 108 are formed on the entire surface above the substrate 101 by vacuum evaporation or the like, and the unnecessary areas are removed by a lift-off method. remove. Thereby, a pad electrode 108 having a predetermined shape is formed.

Through 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 includes a plurality of semiconductor laser elements in which a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer are stacked in this order. It is. A plurality of semiconductor laser elements included in the semiconductor laser device 100 have a first stripe structure (for example, a ridge portion 10R) for confining the current flowing through the first active layer 103, and each semiconductor laser element 10 emits light 400. and a semiconductor laser element 11 that has a second stripe structure (for example, a ridge portion 11R) for confining the current flowing through the second active layer 103a and emits light 401 having a longer wavelength than the light 400. . The semiconductor laser device 100 also includes an external resonator 280 that causes the light 400 to resonate with the semiconductor laser element 10 and the light 401 to resonate with the semiconductor laser element 11. When viewed from the stacking direction, the first stripe width (for example, width L0), which is the width of the first stripe structure at the first end face (emission end face 240) that emits the light 400 in the semiconductor laser element 10, is the width of the first stripe structure in the semiconductor laser element 10. It is smaller than the second stripe width (for example, width L1), which is the width of the second stripe structure at the second end face (output end face 240) of the element 11 that emits the light 401.

In this way, for example, among a plurality of semiconductor laser elements that emit light of 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 Narrow the stripe width of the element. For example, among the semiconductor laser devices 10 and 11, the width L1 of the ridge portion 11R of the semiconductor laser device 11 is made wider than the width L0 of the ridge portion 10R of the semiconductor laser device 10. As a result, the oscillation threshold value can be increased in a semiconductor laser device whose emitted light has a long wavelength. Alternatively, the oscillation threshold can be lowered in a semiconductor laser element whose emitted light has a short wavelength. Therefore, the oscillation thresholds of a plurality of semiconductor laser elements that emit light of different wavelengths can be brought close to each other. Further, according to such a configuration, for example, the waveguide at the first end facet of the semiconductor laser element 11 in which the spot diameter of the light returning from the external resonator 280 (return light) is wide is the waveguide at the second end facet 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 both semiconductor laser devices 10 and 11. As described above, according to the semiconductor laser device 100, in an external cavity type semiconductor laser device including a plurality of semiconductor laser elements, the oscillation thresholds of the plurality of semiconductor laser elements can be made close to each other. Further, according to the semiconductor laser device 100, the coupling efficiency between the feedback light and the waveguide can be increased in both of the semiconductor laser elements 10 and 11, so that 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 uniformly extends with a width L0 in the emission direction of the light 400 in the semiconductor laser device 10, and the ridge portion 11R extends uniformly in the emission direction of the light 400 in the semiconductor laser device 11. It extends uniformly with a width L1 in the emission direction of the light 401.

According to this, the semiconductor laser devices 10 and 11 can be manufactured more easily than when the widths of the ridge portions 10R and 11R are partially changed.

Further, for example, a 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, compared to the case where the semiconductor laser element 10 and the semiconductor laser element 11 are separate bodies, the semiconductor laser device 100 includes the semiconductor laser element 10, the semiconductor laser element 11, the external resonator 280, etc. Easy to align with optical system.

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

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 multiplexer 270 that multiplexes the light 400 and the light 401 and outputs the multiplexed light. That is, the multiplexer 270 multiplexes 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 location by the multiplexer 270.

Further, for example, the multiplexer 270 includes a wavelength dispersion element having a diffraction grating.

According to multiplexing using a wavelength dispersion element, light of different wavelengths is incident on the semiconductor laser element depending on its position. In other words, the wavelengths of 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 of different wavelengths can be brought close to each other, and the coupling efficiency between the feedback light and the waveguide can be improved. can be made high in both the semiconductor laser elements 10 and 11, so that the optical output relative to the input power, that is, the luminous efficiency can be made high. Therefore, the present invention is particularly useful for an external cavity type semiconductor laser device 100 that uses multiplexing using a wavelength dispersion element.

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 device 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 this embodiment, both the first end surface and the second end surface are the output end surface 240, and the distance from the collimator lens is L10.

In this way, for example, by collimating the lights 400 and 401 using the same collimator lens and arranging the semiconductor laser elements 10 and 11 so that the distance from the collimator lens is the same, the semiconductor laser Compared to the case where the arrangement of each of the elements 10 and 11 is changed, manufacturing becomes easier. Here, for example, by collimating the lights 400 and 401 using the same collimator lens and arranging the semiconductor laser elements 10 and 11 so that the distance from the collimator lens is the same, the wavelength of the light 400 can be changed. Since the wavelengths of the light 400 and the light 401 are different, the spot diameter of the return light at the output end face 240 is different between the light 400 and the light 401. However, as described above, according to the semiconductor laser device 100, the coupling efficiency between the feedback light and the waveguide can be increased in both the semiconductor laser elements 10 and 11. Therefore, the present invention provides a semiconductor laser device 100 in which 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 distances from the collimator lens are the same. Particularly useful.

[Modified example]
Modifications of the semiconductor laser device according to the present disclosure will be described below. In the description of the semiconductor laser device according to the modification, components that are substantially the same as those of the semiconductor laser device 100 will be denoted by the same reference numerals, and the description may be partially simplified or omitted. Note that the semiconductor laser device according to the modification differs from the semiconductor laser device 100 in the shape of the ridge portion of the semiconductor laser element, and other parts are substantially the same.

FIG. 8 is a top view showing a semiconductor laser device according to a modified example. Note that although FIG. 8 does not show a cross section, the ridge portion is shown with hatching for explanation.

The semiconductor laser device according to the modification includes a plurality of semiconductor laser elements in which a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer different from the first conductivity type are stacked in this order. For example, the semiconductor laser device according to the modification includes a semiconductor laser element (first semiconductor laser element) 13, a semiconductor laser element (second semiconductor laser element) 14, and a semiconductor laser element (third semiconductor laser element) 15. It includes a semiconductor laser array 203 that is integrally formed. Note that the number of semiconductor laser elements included in the semiconductor laser array 203 is not particularly limited as long as it is plural.

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

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

The ridge portions 13R, 14R, and 15R are constriction portions formed in the semiconductor laser devices 13, 14, and 15 to constrict the current flowing in the active layers of the semiconductor laser devices 13, 14, and 15, respectively. The ridge portions 13R, 14R, and 15R extend in the light emission direction (in this modification, the Y-axis direction). Waveguides are formed below the ridge portions 13R, 14R, and 15R, and light is guided through the waveguides and is emitted from the output end face 240.

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

Here, when viewed from the stacking direction, the ridge portion 13R is located from the first end face (emission end face 240) to the side opposite to the direction in which the light 403 is emitted from the semiconductor laser element 13 (in this embodiment, the Y The width becomes narrower toward the negative axis side). Specifically, the width of the ridge portion 13R becomes narrower from the emission 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) of the ridge portion 13R, which is the width at the emission end face 240 that emits the light 403 in the semiconductor laser element 13, is determined based on FIG. Ru. Thereby, in the semiconductor laser element 13, the coupling efficiency between the waveguide and the feedback light can be increased. Further, by appropriately setting the width of the ridge portion 13R in a portion other than the emission end face 240, the oscillation threshold value can be appropriately set. As described above, for example, by reducing the area of the ridge portion 13R when viewed from the stacking direction, the oscillation threshold can be reduced. Therefore, by narrowing the width toward the side opposite to the direction in which the light 403 is emitted in the semiconductor laser element 13, the coupling efficiency between the waveguide and the feedback light is increased, and the plurality of semiconductor laser elements 13, 14 , 15 oscillation thresholds can be approximated. Further, for example, when viewed from the stacking direction, the ridge portion 13R has a tapered shape whose width gradually narrows toward the Y-axis negative direction side. According to this, the loss of light in the waveguide can be reduced compared to the case where the width suddenly becomes narrower.

Note that, as shown in FIG. 8, when viewed from the stacking direction, the ridge portion 13R has a portion whose width gradually becomes narrower toward the Y-axis negative direction and a portion whose width is uniform. Alternatively, the width may continue to gradually become narrower toward the Y-axis negative direction side.

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

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

For example, the oscillation threshold of the semiconductor laser device 10 shown in FIG. 3 is 225 mA. Further, for example, the oscillation threshold of the semiconductor laser device 11 shown in FIG. 3 is 220 mA. The oscillation threshold of the semiconductor laser device 12 shown in FIG. 3 is 218 mA. In this way, 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 threshold is changed between the semiconductor laser device 10 and the semiconductor laser device 11. and the semiconductor laser element 12 are different.

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

As shown in FIG. 8, the structure is such that the width becomes narrower from the emission end face 240 toward the side opposite to the direction in which the lights 403, 404, and 405 in the semiconductor laser elements 13, 14, and 15 are emitted. This allows the oscillation thresholds of the semiconductor laser elements 13, 14, and 15 to be brought closer to each other.

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

Note that only a part of the ridge portions 13R, 14R, and 15R (for example, the ridge portion 13R of the semiconductor laser element 13 whose emitted light wavelength is the shortest among the semiconductor laser elements 13, 14, and 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 other parts (for example, the ridge parts 14R and 15R) of the semiconductor laser element becomes narrower in the direction in which the light is emitted. It may extend in any direction.

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 wavelength of emitted light is located on the opposite side of the direction in which the light 403 of the semiconductor laser element 13 is emitted. The width of the ridge portion 15R of the semiconductor laser element 15, which has the longest wavelength of emitted light, becomes narrower as it goes toward the opposite side of the direction in which the light 405 is emitted from the semiconductor laser element 15, The ridge portion 14R may have a uniform width extending in the direction in which the light 404 in the semiconductor laser element 14 is emitted.

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

For example, in the above embodiment, the ridge portion is illustrated as the stripe structure, but the stripe structure is not limited to the above-described ridge portion. The stripe structure may be any structure as long as it constricts the current flowing through the active layer, and may be formed as a barrier layer that constricts the current inside the semiconductor laser element, for example.

Further, for example, in the above embodiment, a semiconductor laser array is described in which a plurality of semiconductor laser elements are integrally formed, but a plurality of semiconductor laser elements may be formed individually as separate bodies. In this case, for example, the positions of the light emitting end faces of 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 a semiconductor laser device includes a plurality of semiconductor laser arrays, the plurality of semiconductor laser elements in the semiconductor laser array having a plurality of semiconductor laser elements have the same stripe width, and the plurality of semiconductor laser elements have the same stripe width. The stripe width may be different for each array.

For example, in the above embodiments, a GaN-based semiconductor laser array is described as an example, but GaAs-based, InP-based, or II-VI group semiconductors, etc., which can change the wavelength of the light emitting region, may also be used. Semiconductor laser elements using materials other than the above-mentioned materials may also be used. 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 may be arranged so that their oscillation threshold values are close to each other. , may be used in combination with different stripe widths. In this manner, a semiconductor laser device may include a plurality of semiconductor laser elements made of different materials and having different stripe widths.

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

There are also forms obtained by making various modifications to the above embodiments that those skilled in the art can think of, and forms realized by arbitrarily combining the components and functions of the above embodiments without departing from the spirit of the present disclosure. Included in this disclosure.

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

10, 13 Semiconductor laser device (first semiconductor laser device)
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 conductivity type cladding layer 103 Active layer (first active layer)
103a Second active layer 103b Third active layer 104 Second conductivity type cladding layer 105 Contact layer 106 Insulating layer 107 Second conductive side electrode 108 Pad electrode 109 First conductive side electrode 200, 201, 202, 203, 1000 Semiconductor laser array 240 Output end face 250 Reflection end face 260, 261, 262, 1060 Collimator optical system (collimator lens)
270 Multiplexer (wavelength dispersion element)
280 External resonator (half mirror)
400, 401, 402, 403, 404, 405, 1040, 1041, 1042 Light 1010, 1011, 1012 Semiconductor laser element L0, L1, L2, L3, L4, L5 Width L10 Distance

Claims (10)

A semiconductor laser device comprising a plurality of semiconductor laser elements in which a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer are stacked in this order,
The plurality of semiconductor laser elements are
a first semiconductor laser element having a first stripe structure for confining the current flowing through the first active layer and emitting first light;
a second semiconductor laser element having a second stripe structure for confining the current flowing through the second active layer and emitting second light having a longer wavelength than the first light;
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 first stripe width, which is the width of the first stripe structure at the first end surface from which the first light is emitted in the first semiconductor laser element, is the width of the first stripe structure in the second semiconductor laser element. smaller than the second stripe width, which is the width of the second stripe structure at the second end surface that emits the second light;
A spot diameter of the first light returning from the external resonator on the first end face is smaller than a spot diameter of the second light returning from the external resonator on the second end face.
Semiconductor laser equipment. When viewed from the stacking direction,
The first stripe structure uniformly extends with the first stripe width in the emission direction of the first light in the first semiconductor laser element,
The semiconductor laser device according to claim 1, wherein the second stripe structure uniformly extends with the second stripe width in the emission direction of the second light in the second semiconductor laser element. When viewed from the stacking direction, the width of the first stripe structure becomes narrower from the first end face toward a side opposite to the direction in which the first light is emitted from the first semiconductor laser element. 1. The semiconductor laser device according to 1. The semiconductor laser device according to claim 1, 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 multiplexer that multiplexes the first light and the second light and outputs the combined result. The semiconductor laser device according to claim 6, wherein the multiplexer includes a wavelength dispersion element having a diffraction grating. Further, a collimator lens for collimating the first light and the second light is provided between the first semiconductor laser element, 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 a distance between the first end face and the collimator lens is equal to a distance between the second end face and the collimator lens. A semiconductor laser device comprising a plurality of semiconductor laser arrays in which a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer are stacked in this order,
The plurality of semiconductor laser arrays are
a first semiconductor laser array having a plurality of first stripe structures for confining the current flowing through the first active layer and emitting first light;
a second semiconductor laser array having a plurality of second stripe structures for confining the current flowing through the second active layer and emitting second light having a longer wavelength than the first light;
The semiconductor laser device includes an external resonator that resonates the first light with the first semiconductor laser array and resonates the second light with the second semiconductor laser array ,
When viewed from the stacking direction, the first stripe width , which is the width of the first stripe structure at the first end surface from which the first light is emitted in the first semiconductor laser array, is the width of the first stripe structure in the second semiconductor laser array . A semiconductor laser device, which is smaller than a second stripe width that is a width of the second stripe structure at a second end face that emits the second light.

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