Light-emitting device

Abstract

To provide a light-emitting device that makes it easy to adjust the oscillation wavelength to a desired value. [Solution] The light-emitting device comprises a semiconductor laser array having a plurality of semiconductor laser element sections, including a first semiconductor laser element section and a second semiconductor laser element section, wherein each of the plurality of semiconductor laser element sections comprises a first section including a diffraction grating, a core section, and a second section having cladding sections provided on both sides of the core section and propagating light, the second semiconductor laser element section is arranged to have a higher operating temperature than the first semiconductor laser element section, and the period of the diffraction grating in the second semiconductor laser element section is shorter than the period of the diffraction grating in the first semiconductor laser element section.

Description

[Technical Field]

[0001] This disclosure relates to a light-emitting device. [Background technology]

[0002] Conventionally, array-type semiconductor lasers are known in which multiple stripe-shaped active layers are formed at intervals from each other (see, for example, Patent Document 1). However, the oscillation wavelength of such array-type semiconductor laser elements may change due to temperature changes during operation. In addition, the oscillation wavelength of array-type semiconductor laser elements may deviate from the expected value due to variations in the compositional distribution within the plane. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-147154 [Overview of the project] [Problems that the invention aims to solve]

[0004] This disclosure provides a light-emitting device that allows for easy adjustment of the oscillation wavelength to a desired value. [Means for solving the problem]

[0005] In one embodiment, the light-emitting device includes a semiconductor laser array having a plurality of semiconductor laser element sections, including a first semiconductor laser element section and a second semiconductor laser element section, wherein each of the plurality of semiconductor laser element sections includes a first section including a diffraction grating, a core section, and a second section having cladding sections provided on both sides of the core section for propagating light, the second semiconductor laser element section is arranged to have a higher operating temperature than the first semiconductor laser element section, and the period of the diffraction grating in the second semiconductor laser element section is shorter than the period of the diffraction grating in the first semiconductor laser element section. [Effects of the Invention]

[0006] A light-emitting device that easily adjusts the oscillation wavelength to a desired value is realized.

Brief Description of the Drawings

[0007] [Figure 1] It is a schematic top view of a semiconductor laser array according to Embodiment 1 of the present disclosure. [Figure 2] It is a schematic diagram showing the waveguide structure of the semiconductor laser array according to Embodiment 1 of the present disclosure. [Figure 3] It is a schematic cross-sectional view taken along line III-III of the semiconductor laser element part in the semiconductor laser array of FIG. 1. [Figure 4] It is a schematic cross-sectional view taken along line IV-IV of the semiconductor laser element part in the semiconductor laser array of FIG. 1. [Figure 5] It is a schematic top view of a light-emitting device according to Embodiment 1 of the present disclosure. [Figure 6] It is a schematic top view of the light-emitting device according to Embodiment 1 of the present disclosure with the lid removed. [Figure 7] It is a schematic top view of the light-emitting device according to Embodiment 2 of the present disclosure with the lid removed. [Figure 8] It is a schematic top view of a cooling device according to Embodiment 2 of the present disclosure. [Figure 9] It is a schematic top view of another light-emitting device according to Embodiment 2 of the present disclosure with the lid removed. [Figure 10] It is a schematic top view of another cooling device according to Embodiment 2 of the present disclosure. [Figure 11] It is a schematic diagram showing the waveguide structure of the semiconductor laser array according to Embodiment 3 of the present disclosure.

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments for implementing the present disclosure will be described while referring to the drawings. The following description is for embodying the technical idea of the present disclosure, and without specific description, the present disclosure is not limited to the following description. In the present disclosure, for the sake of easy understanding of the explanation, names such as "upper" and "lower" may be used, but this does not limit the orientation during the use of the light-emitting device, and the orientation of the light-emitting device is arbitrary. In each drawing, members having the same function may be denoted by the same reference numeral. For the sake of explanation of key points or ease of understanding, it may be shown separately in embodiments for convenience, but partial substitution or combination of the configurations shown in different embodiments or Example 1 is possible. In the embodiments shown later, mainly the matters different from the previously shown embodiments will be described, and duplicate explanations for the matters common to the previously shown embodiments may be omitted. The sizes, positional relationships, etc. of the members shown in each drawing may be exaggerated for clarity of explanation.

[0009] <Embodiment 1> FIG. 1 is a schematic top view of a semiconductor laser array 100 according to Embodiment 1 of the present disclosure. FIG. 2 is a schematic diagram showing the waveguide structure of the semiconductor laser array according to Embodiment 1 of the present disclosure. FIG. 3 is a schematic cross-sectional view taken along line III-III of the semiconductor laser element part in the semiconductor laser array of FIG. 1. FIG. 4 is a schematic cross-sectional view taken along line IV-IV of the semiconductor laser element part in the semiconductor laser array of FIG. 1. Hereinafter, each configuration in the light-emitting device 10 of Embodiment 1 will be described in detail with specific examples. Note that the light-emitting device 10 of Embodiment 1 is not limited to the following specific examples as long as it has the basic configuration capable of obtaining the above effects.

[0010] (Light-emitting device 10) The light-emitting device 10 includes a semiconductor laser array 100 having a plurality of semiconductor laser element sections, including a first semiconductor laser element section 101 and a second semiconductor laser element section 102. Each of the plurality of semiconductor laser element sections includes a first section 110 including a diffraction grating 115, a core section 121, and a second section 120 that propagates light and has cladding sections 122 provided on both sides of the core section 121. The second semiconductor laser element section 102 is positioned so that its operating temperature is higher than that of the first semiconductor laser element section 101, and the period of the diffraction grating 115 in the second semiconductor laser element section 102 is shorter than the period of the diffraction grating 115 in the first semiconductor laser element section 101.

[0011] As shown in Figures 1 and 2, the semiconductor laser array 100 has a plurality of semiconductor laser element sections, including a first semiconductor laser element section 101 and a second semiconductor laser element section 102. In the example shown in the figures, the semiconductor laser array 100 further has a third semiconductor laser element section 103. As shown in Figure 2, each of the plurality of semiconductor laser element sections comprises a first section 110 including a diffraction grating 115, a core section 121, and a second section 120 having cladding sections 122 provided on both sides of the core section and propagating laser light. The diffraction grating 115 includes a diffraction grating 115A provided in the first semiconductor laser element section 101, a diffraction grating 115B provided in the second semiconductor laser element section 102, and a diffraction grating 115C provided in the third semiconductor laser element section 103. Furthermore, as shown in Figure 3, each of the multiple semiconductor laser element sections includes a substrate 201, an n-side semiconductor layer 202, an active layer 203, and a p-side semiconductor layer 204. Each of the multiple semiconductor laser element sections may also include an n-side electrode, a p-side electrode 205, a p-side pad electrode 206, an insulating film 207, and a mirror formed on the end face. However, in Figure 3, the n-side electrode, p-side electrode 205, p-side pad electrode 206, insulating film 207, and mirror formed on the end face are omitted from the illustration. In Figure 4, the n-side electrode and the mirror formed on the end face are omitted from the illustration. Furthermore, each of the multiple semiconductor laser element sections has a ridge 210 formed on its upper surface. Each of the multiple semiconductor laser element sections is, for example, an end-face emitting laser element having a light-emitting end face and a light-reflecting end face that intersect with the main surface of the semiconductor layer. The stacking direction of the semiconductor laser element sections may be called upward, and the opposite direction may be called downward. The stacking direction of the semiconductor laser element is the direction of the p-side semiconductor layer 204 relative to the n-side semiconductor layer 202. The semiconductor laser array 100 is made of, for example, a nitride semiconductor, a phosphide semiconductor, or an arsenide semiconductor. The following explanation will use an example where the semiconductor laser array 100 is made of a nitride semiconductor.

[0012] (Circuit board 201) The substrate 201 of the semiconductor laser array 100 in Embodiment 1 is, for example, a semiconductor substrate. The substrate 201 is, for example, a nitride semiconductor substrate such as a GaN substrate. The nitride semiconductor substrate may contain n-type impurities. The elements that constitute the n-type impurities may be, for example, O, Si, or Ge. The substrate 201 can be made of a nitride semiconductor substrate, and its upper surface can be a +c plane (i.e., a (0001) plane). In Embodiment 1, the c plane is not limited to a plane that strictly coincides with the (0001) plane, but also includes a plane having an off-angle of ±1 degree or less, preferably ±0.03 degrees or less. The semiconductor laser array 100 does not have to have a substrate 201. The upper surface of the substrate may be an m plane, an a plane, or an r plane, etc.

[0013] (n-side semiconductor layer 202) The n-side semiconductor layer 202 has one or more semiconductor layers containing n-type impurities. The n-side semiconductor layer 202 may include, for example, an n-side cladding layer 2021 and an n-side guide layer 2022. The n-side semiconductor layer 202 may further have an undoped layer in which impurities are not intentionally doped. The concentrations of n-type and p-type impurities in the undoped layer are below the detection limit in analytical results such as secondary ion mass spectrometry (SIMS). For example, if Si is included as an n-type impurity in the undoped layer, the concentration may be 1 × 10⁻⁶. 16 cm -3 The following applies, and if Ge is present as an n-type impurity, then 1 × 10 17 cm -3 The following is preferable: The refractive index of the n-side cladding layer 2021 is preferably smaller than that of the n-side guide layer 2022. This makes it easier for light to be confined to the n-side guide layer 2022. The n-side cladding layer 2021 is located between the active layer 203 and the substrate 201.

[0014] The n-side cladding layer 2021 may be, for example, a nitride semiconductor layer. Examples of nitride semiconductors include AlGaN or GaN. The thickness of the n-side cladding layer 2021 may be between 0.45 μm and 3.0 μm. The content of n-type impurities is 1 × 10⁻⁶. 17 cm―3 Above 5×10 18 cm ―3 The following may be applicable. The n-side guide layer 2022 is disposed between the active layer 203 and the n-side cladding layer 2021. The n-side guide layer 2022 may be, for example, a nitride semiconductor layer. Examples of the nitride semiconductor include AlGaN, GaN, or InGaN. The film thickness of the n-side guide layer 2022 may be, for example, 0.05 μm or more and 0.5 μm or less. The content rate of the n-type impurity is 1×10 17 cm ―3 Above 5×10 18 cm ―3 The following may be applicable.

[0015] (Active layer 203) The active layer 203 is formed on the n-side guide layer 2022. The active layer 203 emits light having a wavelength of, for example, 360 nm or more and 530 nm or less. The active layer 203 may have a quantum well structure composed of one or more well layers and a plurality of barrier layers. The well layer and the barrier layer are, for example, GaN, InGaN, AlGaN, or AlInGaN. The well layer is, for example, AlGaN, GaN, or InGaN, and is a nitride semiconductor having a smaller bandgap energy than the barrier layer. The active layer 203 may be a multiple quantum well structure or a single quantum well structure. Note that impurities may be contained in either or both of the well layer and the barrier layer.

[0016] (p-side semiconductor layer 204) The p-side semiconductor layer 204 includes one or more semiconductor layers containing a p-type impurity. The p-side semiconductor layer 204 is formed on the active layer 203. The p-side semiconductor layer 204 may include, for example, a p-side guide layer 2041 and a p-side cladding layer 2042 in order from the substrate 201 side (that is, from the active layer 203 side). Note that the p-side semiconductor layer 204 may not include the p-side cladding layer 2042. The p-side semiconductor layer 204 may include other layers. The p-side semiconductor layer 204 may have an undoped layer that is not intentionally doped with impurities. The refractive index of the p-side cladding layer 2042 is preferably smaller than the refractive index of the p-side guide layer 2041. Thereby, light is likely to be confined to the p-side guide layer 2041 side.

[0017] The p-side guide layer 2041 may be, for example, a nitride semiconductor layer. Examples of nitride semiconductors include AlGaN or GaN. The thickness of the p-side guide layer 2041 may be 0.05 μm or more and 0.25 μm or less. The p-side guide layer 2041 may also be an undoped layer, with a thickness of 1 × 10⁻¹⁶. 16 cm ―3 The above 1 x 10 18 cm ―3 The following range may contain p-type impurities. The p-side cladding layer 2042 may be, for example, a nitride semiconductor layer. Examples of nitride semiconductors include AlGaN or GaN. It may be a single-layer structure or a multilayer structure in which nitride semiconductor layers with different compositions are stacked. The p-type impurity content is 1 × 10⁻⁶ 17 cm ―3 The above 1 x 10 20 cm ―3 The following may apply: The p-side cladding layer 2042 may include a p-side contact layer. The p-side contact layer may be, for example, a nitride semiconductor.

[0018] (Ridge 210) Each of the multiple semiconductor laser element sections has a ridge 210 formed on its upper surface. The ridge 210 is provided, for example, on a portion of the upper surface of the p-side semiconductor layer 204. In the illustrated example, the ridge 210 includes a first ridge 210a and a second ridge 210b. The first ridge 210a is provided in the portion that overlaps with the first section 110 in a top view. The second ridge 210b is provided in the second section 120 in a top view, and in a top view, the width of the second ridge 210b in the direction perpendicular to the waveguide direction is narrower than that of the first ridge 210a. The first ridge 210a is provided continuously with the second ridge 210b, for example, such that its central axis in the waveguide direction coincides with the optical axis of the second section 120.

[0019] (p-side electrode 205, p-side pad electrode 206, insulating film 207) The p-side electrode 205 is provided on the upper surface of the ridge 210. The p-side electrode 205 is provided so as to be in contact with the upper surface of the first ridge 210a and the upper surface of the second ridge 210b. The p-side electrode 205 may be provided with the electrode portion connected to the upper surface of the first ridge 210a and the electrode portion connected to the upper surface of the second ridge 210b electrically separated.

[0020] The material of the p-side electrode 205 can be a single-layer or multilayer film of a conductive oxide containing, for example, at least one selected from metals or alloys such as Ni, Rh, Cr, Au, W, Pt, Ti, Al, Zn, In, and Sn. Examples of conductive oxides include ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), and GZO (Gallium-doped Zinc Oxide). The thickness of the electrode can usually be any thickness that allows it to function as an electrode in a semiconductor device. For example, it can be about 0.05 μm to 2 μm.

[0021] The p-side pad electrode 206 is provided above the p-side electrode 205. The material of the p-side pad electrode 206 may be the same as the material of the p-side electrode 205, for example.

[0022] The insulating film 207 is provided above the p-side electrode 205. The insulating film 207 is a component that does not conduct current and restricts the path through which current flows. Examples of materials for the insulating film 207 include SiO2, Al2O3, or AlN.

[0023] (Part 1 110) The first section 110 is a portion that includes an emission end face for emitting light and is provided with a diffraction grating 115. The first section 110 may be a slab waveguide. That is, in the first section 110, light confinement may be limited to the stacking direction only. Because the first section 110 is a slab waveguide and is provided with a diffraction grating 115, the equivalent refractive index will be approximately the same even for different transverse modes, and the selected wavelengths (Bragg wavelengths) at the diffraction grating 115 will be aligned.

[0024] (Diffraction grating 115) The diffraction grating 115 is provided in the first portion 110, as shown in Figure 2, etc. The diffraction grating 115 includes, for example, a diffraction grating 115A provided in the first semiconductor laser element portion 101, a diffraction grating 115B provided in the second semiconductor laser element portion 102, and a diffraction grating 115C provided in the third semiconductor laser element portion 103. In the semiconductor laser element portion of Embodiment 1, the width of the diffraction grating 115 is greater than the width of the core portion 121 when viewed from above. This structure reduces the variation in the oscillation wavelength of light incident on the diffraction grating 115 from the core portion 121. In particular, when the second portion has a structure that propagates laser light in multiple transverse modes, the fact that the width of the diffraction grating 115 is greater than the width of the core portion 121 reduces the variation in equivalent refractive index due to different transverse mode orders, and thus reduces the variation in wavelength selection by the diffraction grating 115.

[0025] The distance between the two ends of the diffraction grating 115 is, for example, 1.5 to 100 times the width of the core portion 121, and more preferably 3 to 10 times. That is, if the width of the core portion 121 is, for example, 15 μm to 100 μm, then the distance between the two ends of the diffraction grating 115 is 22.5 μm to 10000 μm, more preferably 45 μm to 1000 μm, and even more preferably 45 μm to 500 μm. The distance between the two ends of the diffraction grating 115 may be constant, or it may be increased from the second portion 120 side toward the laser light emission end face side of the first portion 110. The diffraction grating 115 can be formed by alternately (periodically) providing members with different refractive indices in the direction of light propagation.

[0026] The diffraction grating 115 may be provided, for example, between two adjacent semiconductor layers, on the p-side semiconductor layer 204, or on the n-side semiconductor layer 202. The diffraction grating 115 may be provided, for example, between the n-side cladding layer 2021 and the n-side guide layer 2022. Specifically, the diffraction grating 115 is provided on the surface of the n-side cladding layer 2021 and alternately includes one or more first protrusions projecting toward the n-side guide layer 2022, and one or more second protrusions provided on the surface of the n-side guide layer 2022 and projecting toward the n-side cladding layer 2021, in the direction of light propagation. The period of the diffraction grating 115 can be appropriately selected considering the wavelength of light emitted by the active layer 203. The period of the diffraction grating 115 may be, for example, 60 nm to 400 nm, preferably 70 nm to 300 nm. The differences in the period of the diffraction grating 115 for each different semiconductor laser element section will be described in detail later.

[0027] (Second part 120) The waveguide structure of the second part 120 is a waveguide for propagating light, having a core portion 121 and cladding portions 122 located on both sides of the core portion 121. The second part 120 may propagate light along the longitudinal direction of the core portion 121 in multiple transverse modes (i.e., transverse multimodes). This allows the semiconductor laser element to have a high output. The number of transverse modes is determined by the width of the core portion 121 and the difference between the refractive index of the core portion 121 and the refractive index of the cladding portion 122. The width of the core portion 121 is defined in a plane perpendicular to the optical axis of the waveguide, in a direction perpendicular to the stacking direction of the semiconductor laser element. The thickness of the core portion 121 is the thickness in the stacking direction of the semiconductor laser element in a plane perpendicular to the optical axis of the waveguide.

[0028] In Embodiment 1, the core portion 121 overlaps with the second ridge 210b in a top view and is a portion set based on the width of the second ridge 210b, and includes at least an n-side semiconductor layer 202, an active layer 203, and a p-side semiconductor layer 204. The cladding portion 122 is a portion sandwiching the core portion 121 and includes at least an n-side semiconductor layer 202, an active layer 203, and a p-side semiconductor layer 204. The refractive index of the core portion 121 and the refractive index of the cladding portion 122 are equivalent refractive indices focusing on the height direction of each portion.

[0029] (Semiconductor laser array 100) As shown in Figure 1, the semiconductor laser array 100 has a plurality of semiconductor laser element sections, including a first semiconductor laser element section 101 and a second semiconductor laser element section 102. In the example shown in the figure, the plurality of semiconductor laser element sections are integrally formed in the semiconductor laser array 100. Each of the plurality of semiconductor laser element sections has an emission end face that emits laser light forward. Each emission end face is, for example, on the same plane. When the plurality of semiconductor laser element sections includes three or more semiconductor laser element sections, the plurality of semiconductor laser element sections are, for example, arranged at the same interval. The first semiconductor laser element section 101 and the second semiconductor laser element section 102 are, for example, adjacent to each other. A separation groove is provided between the adjacent semiconductor laser element sections. The plurality of semiconductor laser element sections may further include a third semiconductor laser element section 103. The third semiconductor laser element section 103 is, for example, provided adjacent to the second semiconductor laser element section 102. In other words, the first semiconductor laser element section 101, the second semiconductor laser element section 102, and the third semiconductor laser element section 103 are arranged in this order. Furthermore, the number of semiconductor laser element sections may be, for example, 2 or more and 60 or less.

[0030] (Light-emitting device 10) As shown in Figure 6, the light-emitting device 10 includes a semiconductor laser array 100. The light-emitting device 10 may also include, for example, a first heat dissipation unit 301 for dissipating heat from a first semiconductor laser element unit 101, and a second heat dissipation unit 302 for dissipating heat from a second semiconductor laser element unit 102. The provision of the first heat dissipation unit 301 and the second heat dissipation unit 302 stabilizes the driving of the first semiconductor laser element unit 101 and the second semiconductor laser element unit 102. In the example shown in the figure, the first heat dissipation unit 301 and the second heat dissipation unit 302 include a submount 310. By including the submount 310 in the first heat dissipation unit 301 and the second heat dissipation unit 302, the semiconductor laser array 100 can be efficiently dissipated while increasing the height of the emission end face of the semiconductor laser array 100. The submount 310 may be integrally formed. That is, the semiconductor laser array 100 may be placed on a single submount 310. Alternatively, one semiconductor laser array 100 may be arranged on multiple submounts 310. In either case, the portion of the submount 310 that overlaps with the first semiconductor laser element portion 101 when viewed from above may be defined as the first heat dissipation portion 301, and the portion of the submount 310 that overlaps with the second semiconductor laser element portion 102 when viewed from above may be defined as the second heat dissipation portion 302. Furthermore, the number of heat dissipation portions may correspond to each semiconductor laser element portion, and the same number as the number of semiconductor laser element portions may be provided.

[0031] The submount 310 is, for example, configured in the shape of a rectangular parallelepiped and has a bottom surface, a top surface, and one or more sides. Part or all of the submount 310 may be formed from at least one selected from the group consisting of, for example, AlN, SiC, Al2O3, graphene, diamond, CuW, Cu, Cu / AlN / Cu laminated structures, and Metal Matrix Compound (MMC). The MMC includes, for example, at least one selected from the group consisting of Cu, Ag, or Al, and diamond. Alternatively, part or all of the submount 310 may be formed from other common materials. The thermal conductivity of the submount 310 may be, for example, 10 [W / m·K] or more and 2500 [W / m·K] or less, and preferably 100 [W / m·K] or more and 2500 [W / m·K] or less. Due to its thermal conductivity, the submount 310 can efficiently dissipate the heat emitted from the semiconductor laser array 100 during operation.

[0032] The thermal expansion coefficient of submount 310 is, for example, 2 × 10 -6 [1 / K] or more 2×10 -5 The thermal expansion coefficient may be less than [1 / K]. Such a coefficient of thermal expansion reduces the risk of deformation of the submount 310 due to the heat applied when the semiconductor laser array 100 is bonded to the submount 310 with a bonding material. A metal film with a thickness of, for example, 0.5 μm to 10 μm may be formed on the upper and lower surfaces of the submount 310 by, for example, plating.

[0033] (Other components) In the example shown in Figures 5 and 6, the light-emitting device 10 includes a package 350, a reflective member 360, a wire 370, and a lid 380. The package 350 has a base 351 and a frame 352. The base 351 has an upper surface and a lower surface. A submount 310 is placed on the upper surface of the base 351, for example, via a bonding material. The base 351 can be formed primarily from a metal. Examples of metals that can be used include Cu or alloys containing Cu. The base 351 may also be formed from a main material other than metal, for example, from ceramics. A metal film may be provided on the upper surface of the base 351.

[0034] The frame portion 352 has an upper surface, a lower surface, one or more inner surfaces, and one or more outer surfaces. The frame portion 352 is, for example, rectangular in shape when viewed from above. One or more inner surfaces of the frame portion 352 are connected to the upper surface and extend downward from the upper surface. One or more outer surfaces of the frame portion 352 are connected to the upper and lower surfaces of the frame portion 352. When viewed from above, the frame portion 352 surrounds the semiconductor laser array 100.

[0035] The frame portion 352 has a stepped portion 353 having an upper surface located above the upper surface of the base portion 351 and below the upper surface of the frame portion 352. The stepped portion 353 has an inner surface that connects to the upper surface of the stepped portion 353 and extends downward. The upper surface of the stepped portion 353 connects to one or more inner surfaces of the frame portion 352. The upper surface of the stepped portion 353 may be parallel to, for example, the upper surface of the base portion 351. The inner surface of the stepped portion 353 connects to, for example, the upper surface of the base portion 351. The stepped portion 353 may be provided along the inner surface of the frame portion 352 when viewed from above.

[0036] The frame portion 352 can be formed using a different material as its main material, for example, than the base portion 351. Ceramics are an example of a main material used to form the frame portion 352. For example, AlN, Si3N4, Al2O3, or SiC can be used as the ceramic material.

[0037] The reflective member 360 is a component that reflects light emitted from the semiconductor laser array 100 and changes the direction of light propagation. In the illustrated example, the reflective member 360 reflects the light emitted from the semiconductor laser array 100 upward. The reflective member 360 comprises a bottom surface, a reflective surface that reflects light, and a plurality of side surfaces connected to the reflective surface and the bottom surface. In the illustrated example, the bottom surface, the reflective surface, and the plurality of side surfaces are all planar. In side view, the reflective member 360 may be triangular. In particular, in side view, the reflective member 360 may be a triangle with chamfered corners.

[0038] The reflective member 360 can use glass or metal as the main material that forms its outer shape. The main material is preferably a heat-resistant material, such as glass such as quartz or BK7 (borosilicate glass), metal such as Al, or Si. The reflective surface a may also be provided with, for example, a metal or a dielectric multilayer film. Examples of metals include Ag and Al. Examples of dielectric multilayer film materials include Ta2O5 / SiO2, TiO2 / SiO2, and Nb2O5 / SiO2.

[0039] The wire 370 is a component for supplying current to the semiconductor laser array 100. In the illustrated example, the wire 370 electrically connects the upper surface of the stepped portion 353 to the upper surface of the semiconductor laser array 100 or the submount 310. Examples of materials for the wire 370 include Au, Ag, Cu, Al, and W.

[0040] The lid portion 380 has an upper surface, a lower surface, and one or more side surfaces that intersect the upper and lower surfaces. The one or more side surfaces connect the outer edge of the upper surface to the outer edge of the lower surface. In the illustrated example, the lid portion 380 has a light-transmitting portion 381 and a light-shielding portion 382 provided with a metal film. The light-transmitting portion 381 is a portion for transmitting light emitted from the semiconductor laser array 100 and reflected by the reflecting member 360. The light-shielding portion 382 is a portion for blocking stray light. The lid portion 380 and the package 350 form an airtight space. By placing the semiconductor laser array 100 inside the airtight space, the semiconductor laser array 100 can be protected from contamination.

[0041] (Relationship between the period of the diffraction grating and the temperature of the semiconductor laser element during operation) In a semiconductor laser element having a diffraction grating 115, the wavelength (Bragg wavelength λ) is strengthened by the diffraction grating 115. B The relationship between the period Λ of the diffraction grating 115 and the equivalent refractive index n of the diffraction grating 115, as shown in Equation 1 below, holds. Note that the equivalent refractive index of the diffraction grating 115 refers to the effective refractive index obtained by considering the optical confinement in the stacking direction of the semiconductor laser element and further averaging the modulation component of the refractive index of the diffraction grating.

[0042] λ B =2×Λ×n (Formula 1)

[0043] In other words, the Bragg wavelength can be determined by the period Λ of the diffraction grating 115 and the equivalent refractive index n. The Bragg wavelength can be adjusted by adjusting the period of the diffraction grating 115 to an arbitrary value.

[0044] Incidentally, each of the multiple semiconductor laser element sections may reach different temperatures depending on the operating conditions. For example, if the first heat dissipation section 301 and the second heat dissipation section 302 are made of different materials or have different volumes, the operating temperature of the second semiconductor laser element section 102 may be higher than that of the first semiconductor laser element section 101. Also, for example, if the multiple semiconductor laser element sections further include a third semiconductor laser element section 103, the second semiconductor laser element section 102 will be sandwiched between semiconductor laser element sections on both sides. Since the semiconductor laser element sections act as heat sources, comparing the first semiconductor laser element section 101, which has a semiconductor laser element section adjacent to it on one side, with the second semiconductor laser element section 102, which is sandwiched between semiconductor laser element sections on both sides, the operating temperature of the second semiconductor laser element section 102 may be higher than that of the first semiconductor laser element section 101. In other words, the second semiconductor laser element section 102 is positioned so that its operating temperature is higher than that of the first semiconductor laser element section 101.

[0045] Semiconductor laser elements tend to have a higher refractive index as their operating temperature increases. This is also true for diffraction gratings. Therefore, if the operating temperature of the second semiconductor laser element section 102 is higher than that of the first semiconductor laser element section 101, the refractive index of the second semiconductor laser element section 102 will be higher than that of the first semiconductor laser element section 101. In this case, if the period of the diffraction grating 115A provided in the first semiconductor laser element section 101 and the period of the diffraction grating 115B provided in the second semiconductor laser element section 102 are the same, the degree of change in refractive index will be different, resulting in the oscillation wavelength of the second semiconductor laser element section 102 becoming longer than that of the first semiconductor laser element section 101.

[0046] On the other hand, in the semiconductor laser element section, as can be seen from Equation 1, the Bragg wavelength can be shortened by shortening the period of the diffraction grating 115. Therefore, by shortening the period of the diffraction grating 115B in the second semiconductor laser element section 102, the lengthening of the oscillation wavelength in the second semiconductor laser element section 102 can be mitigated. Consequently, by making the period of the diffraction grating 115B in the second semiconductor laser element section 102 shorter than the period of the diffraction grating 115A in the first semiconductor laser element section 101, the Bragg wavelength in the second semiconductor laser element section 102 can be made the same as the Bragg wavelength in the first semiconductor laser element section 101.

[0047] The period of the diffraction grating 115 can be adjusted arbitrarily. Therefore, by recognizing the temperature distribution of each of the multiple semiconductor laser elements during operation in advance, and shortening the period of the diffraction grating 115 for semiconductor laser elements with higher operating temperatures, the oscillation wavelength of each of the multiple semiconductor laser elements can be adjusted to a desired value. In this case, for example, the gain wavelengths of the multiple semiconductor laser elements may be the same. This makes it possible to obtain multiple laser beams with the same gain wavelength even if there is variation in the operating temperatures of the multiple semiconductor laser elements. Note that "same wavelength" includes, for example, the case where the difference between the maximum and minimum peak wavelengths of the multiple laser beams is 0.3 nm or less.

[0048] The operating temperature of each of the multiple semiconductor laser elements can be recognized, for example, by the following method. First, a semiconductor laser array is created in which the diffraction grating period of each semiconductor laser element is the same, separate from the semiconductor laser array 100 to be installed in the light-emitting device 10, and it is placed on the submount 310. Then, the same current that will be supplied when actually driving the light-emitting device 10 is passed through it and it is driven. At this time, if the operating temperature of the multiple semiconductor laser elements is constant regardless of location, the oscillation wavelength will be the same. However, in reality, the oscillation wavelength will shift for each semiconductor laser element due to the temperature distribution. Therefore, the deviation of the oscillation wavelength of the semiconductor laser element from the expected value can be measured, and the operating temperature of each semiconductor laser element can be recognized using that value. However, the method for recognizing the operating temperature of each of the multiple semiconductor laser elements is not limited to this. A semiconductor laser array 100 with the period of the diffraction grating 115 set based on the temperature distribution of the recognized semiconductor laser elements can be created and installed in the light-emitting device 10.

[0049] (Embodiment 2) Next, the light-emitting device 20 according to Embodiment 2 will be described with reference to Figures 7 to 10. The light-emitting device 20 according to Embodiment 2 differs from the light-emitting device 10 according to Embodiment 1 in that it is equipped with a cooling device 410.

[0050] Figure 7 is a schematic top view of the light-emitting device 20 according to Embodiment 2 of this disclosure with the lid portion 380 removed. Figure 8 is a schematic top view of the cooling device according to Embodiment 2 of this disclosure. Figure 9 is a schematic top view of another light-emitting device according to Embodiment 2 of this disclosure with the lid portion removed. Figure 10 is a schematic top view of another cooling device according to Embodiment 2 of this disclosure. The individual components of the light-emitting device 20 will be described below. Content that overlaps with Embodiment 1 will be omitted as appropriate.

[0051] The light-emitting device 20 may include, for example, a first heat dissipation unit 301 for dissipating heat from the first semiconductor laser element unit 101, and a second heat dissipation unit 302 for dissipating heat from the second semiconductor laser element unit 102. In the example shown in Figures 7 to 10, the first heat dissipation unit 301 and the second heat dissipation unit 302 include a cooling device 410. The cooling device 410 includes a cooling tank 411 and a coolant 412. The cooling tank 411 is a component that houses the coolant 412 inside. The cooling tank 411 may have, for example, cooling pipes for flowing the coolant 412. The coolant 412 is, for example, a liquid that flows through a path including the cooling pipes. The coolant 412 may be, for example, a pure substance or a mixture containing at least one selected from the group consisting of water, oil, ethylene glycol, propylene glycol, and fluorocarbons. By using a cooling device 410 containing a coolant 412 for heat dissipation, the semiconductor laser array 100 can be cooled efficiently.

[0052] The cooling tubes of the cooling device 410 may be provided at least one for each of the multiple semiconductor laser element sections, or one or more cooling tubes may be provided to cool part or all of the multiple semiconductor laser element sections. In either case, the portion of the cooling device 410 that overlaps with the first semiconductor laser element section 101 in a top view may be defined as the first heat dissipation section 301, and the portion of the cooling device 410 that overlaps with the second semiconductor laser element section 102 in a top view may be defined as the second heat dissipation section 302. In Figures 7 and 8, the cooling tubes are provided so that the coolant 412 flows in a meandering manner. In Figures 9 and 10, the cooling tubes are provided so that the coolant 412 flows in a straight line. The shape of the cooling tubes is not limited to these. In Figures 7 to 10, the flow direction of the coolant 412 is indicated by an arrow, but the flow direction of the coolant 412 is not limited to this.

[0053] Even in the light-emitting device 20 including the cooling device 410, each of the multiple semiconductor laser element sections may reach different temperatures depending on the operating conditions. For example, if one cooling pipe is provided to cool multiple semiconductor laser element sections, the heat dissipation capacity of the coolant 412 decreases as it moves downstream. Therefore, if the first heat dissipation section 301 is provided on the upstream side of the flow path and the second heat dissipation section 302 is provided on the downstream side of the flow path, the heat dissipation capacity of the second heat dissipation section may be lower than that of the first heat dissipation section. In that case, the operating temperature of the second semiconductor laser element section 102 may be higher than the operating temperature of the first semiconductor laser element section 101. Also, for example, the cooling device 410 may have one cooling pipe for each of the multiple semiconductor laser element sections, and the multiple semiconductor laser element sections may further have a third semiconductor laser element section 103. In such a case, when comparing the first semiconductor laser element section 101, which has a semiconductor laser element section adjacent to one side, with the second semiconductor laser element section 102, which is sandwiched between semiconductor laser element sections on both sides, the operating temperature of the second semiconductor laser element section 102 may be higher than that of the first semiconductor laser element section 101.

[0054] Even in such a case, by making the period of the diffraction grating 115B in the second semiconductor laser element 102 shorter than the period of the diffraction grating 115A in the first semiconductor laser element 101, the Bragg wavelength in the second semiconductor laser element 102 can be made shorter than the Bragg wavelength in the first semiconductor laser element 101. Therefore, the lengthening of the oscillation wavelength in the second semiconductor laser element 102 can be mitigated by the diffraction grating 115B.

[0055] (Embodiment 3) Next, with reference to Figure 11, a light-emitting device 30 according to Embodiment 3 will be described. The light-emitting device 30 according to Embodiment 3 comprises a semiconductor laser array 100 having a plurality of semiconductor laser element sections, including a first semiconductor laser element section 101 and a second semiconductor laser element section 102. Each of the plurality of semiconductor laser element sections comprises a first section 110 including a diffraction grating 115, and a second section 120 that includes an active layer 203, a core section 121, and cladding sections 122 provided on both sides of the core section 121, and propagates light. The In content in the active layer 203 of the second semiconductor laser element section 102 is higher than the In content in the active layer 203 of the first semiconductor laser element section 101. The period of the diffraction grating 115B in the second semiconductor laser element section 102 is the same as the period of the diffraction grating 115A in the first semiconductor laser element section 101.

[0056] The light-emitting device 30 according to Embodiment 3 describes the relationship between the In content in the active layer 203 of the first semiconductor laser element section 101 and the active layer 203 of the second semiconductor laser element section 102 and the plurality of diffraction gratings 115.

[0057] Each active layer 203 of multiple semiconductor laser element sections may contain different amounts of In depending on the manufacturing conditions. For example, when a semiconductor laser array 100 is manufactured by cutting it from a single wafer, if the original wafer had a bias in the In composition distribution due to the manufacturing conditions, that bias will be carried over to the semiconductor laser array 100. As a result, for example, the In content in the active layer 203 of the second semiconductor laser element section 102 may be higher than the In content in the active layer 203 of the first semiconductor laser element section 101.

[0058] In semiconductor laser elements, the oscillation wavelength tends to shift to longer wavelengths as the In content in the active layer 203 increases. Therefore, when the In content in the active layer 203 of the second semiconductor laser element section 102 is higher than that of the first semiconductor laser element section 101, the oscillation wavelength when the second semiconductor laser element section 102 is driven becomes longer than the oscillation wavelength when the first semiconductor laser element section 101 is driven. In this case, if diffraction gratings 115 are not provided in the first semiconductor laser element section 101 and the second semiconductor laser element section 102, the lengthening of the oscillation wavelength is not mitigated by the diffraction gratings 115, and the oscillation wavelength when the second semiconductor laser element section 102 is driven becomes longer than the oscillation wavelength when the first semiconductor laser element section 101 is driven.

[0059] Even in such cases, by providing diffraction gratings 115 in multiple semiconductor laser element sections and making the period of the diffraction grating 115B in the second semiconductor laser element section 102 the same as the period of the diffraction grating 115A in the first semiconductor laser element section 101, the Bragg wavelength in the second semiconductor laser element section 102 can be made the same as the Bragg wavelength in the first semiconductor laser element section 101. Therefore, the lengthening of the oscillation wavelength in the second semiconductor laser element section 102 can be mitigated by the diffraction grating 115B. Note that "same period" includes, for example, the case where the difference between the maximum and minimum values ​​of the periods of the multiple diffraction gratings 115 is 0.06 nm or less.

[0060] Although preferred embodiments have been described in detail above, the embodiments described above are not limited to those described above. Without departing from the scope described in the claims, the invention relates to the embodiments described above. Various transformations and substitutions can be applied.

[0061] Embodiments of this disclosure may include the following configurations: (Section 1) A semiconductor laser array having a plurality of semiconductor laser element sections, including a first semiconductor laser element section and a second semiconductor laser element section, Each of the aforementioned plurality of semiconductor laser element sections is, The first part includes a diffraction grating, It comprises a core portion and a second portion having cladding portions provided on both sides of the core portion, which propagates light, The second semiconductor laser element is arranged such that its operating temperature is higher than that of the first semiconductor laser element. A light-emitting device wherein the period of the diffraction grating in the second semiconductor laser element is shorter than the period of the diffraction grating in the first semiconductor laser element. (Section 2) It comprises a first heat dissipation section for dissipating heat from the first semiconductor laser element section, and a second heat dissipation section for dissipating heat from the second semiconductor laser element section, The light-emitting device according to item 1, wherein the heat dissipation capacity of the second heat dissipation section is lower than the heat dissipation capacity of the first heat dissipation section. (Section 3) The semiconductor light-emitting element according to item 2, wherein the first heat dissipation element and the second heat dissipation element include a submount. (Section 4) The semiconductor light-emitting element according to claim 2, wherein the first heat dissipation element and the second heat dissipation element include a cooling device. (Section 5) A semiconductor laser array having a plurality of semiconductor laser element sections, including a first semiconductor laser element section and a second semiconductor laser element section, Each of the aforementioned plurality of semiconductor laser element sections is, The first part includes a diffraction grating, It comprises an active layer, a core portion, and a second portion having cladding portions provided on both sides of the core portion, which propagates light, The In content in the active layer of the second semiconductor laser element is higher than the In content in the active layer of the first semiconductor laser element. A light-emitting device in which the period of the diffraction grating in the second semiconductor laser element is the same as the period of the diffraction grating in the first semiconductor laser element. (Section 6) The second part is a semiconductor light-emitting element according to any one of items 1 to 5, which propagates laser light in multiple transverse modes. (Section 7) The light-emitting device according to any one of claims 1 to 6, wherein, in a top view, the width of the diffraction grating is greater than the width of the core portion. (Section 8) The first part is a slab waveguide, as described in any one of items 1 to 7. (Section 9) The light-emitting device according to any one of items 1 to 8, wherein the gain wavelengths of the plurality of semiconductor laser elements are the same. [Explanation of Symbols]

[0062] 10, 20, 30 Light-emitting devices 100 Semiconductor Laser Arrays 101 First semiconductor laser element section 102 Second Semiconductor Laser Element Section 103 Third Semiconductor Laser Element Section 110 Part 1 115 Diffraction grating 120 Part 2 121 Core section 122 Clad section 201 circuit board 202 n-side semiconductor layer 2021 n-side cladding layer 2022 n-side guide layer 203 Active layer 204 p-side semiconductor layer 2041 p-side guide layer 2042 p-side cladding layer 210 Ridge 210a First Ridge 210b Second Ridge 301 1st heat dissipation section 302 Second heat dissipation section 310 Submount 350 packages 351 Base 352 Frame section 353 Stepped section 360 reflective material 370 wire 380 Lid 381 Translucent part 382 Shading area 410 Cooling device 411 Cooling tank 412 Coolant

Claims

1. A semiconductor laser array having a plurality of semiconductor laser element sections, including a first semiconductor laser element section and a second semiconductor laser element section, Each of the aforementioned plurality of semiconductor laser element sections is, The first part includes a diffraction grating, It comprises a core portion and a second portion having cladding portions provided on both sides of the core portion, which propagates light, The second semiconductor laser element is arranged such that its operating temperature is higher than that of the first semiconductor laser element. A light-emitting device wherein the period of the diffraction grating in the second semiconductor laser element is shorter than the period of the diffraction grating in the first semiconductor laser element.

2. It comprises a first heat dissipation section for dissipating heat from the first semiconductor laser element section, and a second heat dissipation section for dissipating heat from the second semiconductor laser element section, The light-emitting device according to claim 1, wherein the heat dissipation capacity of the second heat dissipation section is lower than the heat dissipation capacity of the first heat dissipation section.

3. The light-emitting device according to claim 2, wherein the first heat dissipation section and the second heat dissipation section include a submount.

4. The light-emitting device according to claim 2, wherein the first heat dissipation section and the second heat dissipation section include a cooling device.

5. A semiconductor laser array having a plurality of semiconductor laser element sections, including a first semiconductor laser element section and a second semiconductor laser element section, Each of the aforementioned plurality of semiconductor laser element sections is, The first part includes a diffraction grating, It comprises an active layer, a core portion, and a second portion having cladding portions provided on both sides of the core portion, which propagates light, The In content in the active layer of the second semiconductor laser element is higher than the In content in the active layer of the first semiconductor laser element. A light-emitting device in which the period of the diffraction grating in the second semiconductor laser element is the same as the period of the diffraction grating in the first semiconductor laser element.

6. The second part is a light-emitting device according to any one of claims 1 to 5, which propagates laser light in multiple transverse modes.

7. The light-emitting device according to any one of claims 1 to 5, wherein, in a top view, the width of the diffraction grating is greater than the width of the core portion.

8. The light-emitting device according to any one of claims 1 to 5, wherein the first part is a slab waveguide.

9. The light-emitting device according to any one of claims 1 to 5, wherein the gain wavelengths of the plurality of semiconductor laser elements are the same.

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