Light-emitting device

Abstract

To provide a light-emitting device with improved power conversion efficiency. [Solution] The light-emitting device is a semiconductor laser element having a semiconductor laminate having an active layer and a waveguide structure, and having a front end surface, wherein the semiconductor laminate includes (i) a first portion that includes the front end surface and, in a top view, has a core portion and cladding portions provided on both sides of the core portion, and extends in a first direction which is the normal direction to the front end surface, and (ii) a second portion that includes a diffraction grating and, in a top view, has a width in a second direction perpendicular to the first direction of the diffraction grating that is greater than that of the core portion, and the semiconductor laser element is arranged on a submount, wherein in a top view, the front end surface of the semiconductor laser element does not overlap with the submount, and the second portion of the semiconductor laser element overlaps with the submount.

Description

[Technical Field]

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

[0002] In recent years, there has been a demand for higher output laser light from semiconductor laser elements. High-output semiconductor laser elements are being used, for example, as light sources for processing. For example, Patent Document 1 discloses a multi-transverse-mode laser that can prevent optical damage on the stripe side. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2011-151238 [Overview of the project] [Problems that the invention aims to solve]

[0004] This disclosure aims to provide a light-emitting device with improved power conversion efficiency. [Means for solving the problem]

[0005] In one embodiment, the light-emitting device is a semiconductor laser element having a semiconductor laminate having a waveguide structure and an active layer, wherein the semiconductor laminate has a front end surface, and the semiconductor laminate includes (i) a first portion that includes the front end surface and, in a top view, has a core portion and cladding portions provided on both sides of the core portion, and extends in a first direction which is the normal direction to the front end surface, and (ii) a second portion that includes a diffraction grating and, in a top view, has a width in a second direction perpendicular to the first direction of the diffraction grating that is greater than that of the core portion, and the semiconductor laser element is arranged on a submount, wherein in a top view, the front end surface of the semiconductor laser element does not overlap with the submount, and the second portion of the semiconductor laser element overlaps with the submount. [Effects of the Invention]

[0006] A light-emitting device with improved power conversion efficiency can be provided.

Brief Description of the Drawings

[0007] [Figure 1] It is a schematic top view of a semiconductor laser element according to Embodiment 1 of the present disclosure. [Figure 2] It is a schematic diagram showing the waveguide structure of the semiconductor laser element according to Embodiment 1 of the present disclosure. [Figure 3] It is a schematic cross-sectional view taken along the III-III line of the semiconductor laser element in FIG. 1. [Figure 4] It is a schematic cross-sectional view taken along the IV-IV line of the semiconductor laser element in 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 view showing only the submount and the semiconductor laser element among the schematic cross-sectional views taken along the VII-VII line of the light-emitting device in FIG. 6. [Figure 8] It is a schematic diagram showing the waveguide structure of the semiconductor laser element according to Modification 1 of the present disclosure. [Figure 9] It is an enlarged view of a part of the diffraction grating in FIG. 7. [Figure 10] It is a schematic diagram showing the waveguide structure of the semiconductor laser element according to Modification 2 of the present disclosure. [Figure 11] It is an enlarged view of a part of the diffraction grating in FIG. 9.

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 unless otherwise specified, the present disclosure is not limited to the following description. In the present disclosure, for ease of explanation, terms such as "above" and "below" 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 numerals. For the sake of clarity in explanation or ease of understanding, the embodiments may be shown separately 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 of 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 element 100 according to Embodiment 1 of the present disclosure. FIG. 2 is a schematic diagram showing the waveguide structure of the semiconductor laser element 100 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 100 in FIG. 1. FIG. 4 is a schematic cross-sectional view taken along line IV-IV of the semiconductor laser element 100 in 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 an active layer 203 and a semiconductor laminate having a waveguide structure, and includes a semiconductor laser element 100 having a front end surface. The semiconductor laminate includes (i) a first portion 110 that includes a front end surface 111 and, in a top view, has a core portion 115 and cladding portions 116 provided on both sides of the core portion 115, and extends in a first direction which is the normal direction of the front end surface 111; and (ii) a second portion 120 that includes a diffraction grating 125 and, in a top view, has a width in a second direction perpendicular to the first direction greater than that of the core portion 115. The light-emitting device 10 also includes a submount 310 on which the semiconductor laser element 100 is arranged. In a top view, the front end surface 111 of the semiconductor laser element 100 does not overlap with the submount 310, while the second portion 120 of the semiconductor laser element 100 overlaps with the submount 310.

[0011] As shown in Figure 1, the semiconductor laser element 100 has a first portion 110 and a second portion 120. In the example shown in the figure, the semiconductor laser element 100 has a ridge 210 including a first ridge 210a and a second ridge 210b. The first portion 110 also includes a front end surface 111. An anti-reflective coating 112 may be provided on the front end surface 111. The second portion 120 includes a rear end surface 121. Furthermore, a reflective coating 126 is provided on the rear end surface 121. In the example shown in the figure, as shown in Figure 2, the semiconductor laser element 100 has a core portion 115 and cladding portions 116 provided on both sides of the core portion 115, and comprises a first portion 110 that propagates laser light and a second portion 120 that includes a diffraction grating 125. However, in Figure 7, the anti-reflective coating 112 and the reflective coating 126 are omitted from the illustration. Furthermore, as shown in Figures 3 and 4, the semiconductor laser element 100 includes a substrate 201, a first conductive semiconductor layer, an active layer 203, and a second conductive semiconductor layer. The semiconductor stack includes the first conductive semiconductor layer and a second conductive semiconductor layer provided on the opposite side of the active layer 203 from the first conductive semiconductor layer. The first conductive semiconductor layer is a structure consisting of one or more layers, each containing a layer with impurities of a first conductivity type. However, the first conductive semiconductor layer may also 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). The second conductive semiconductor layer is a structure consisting of one or more layers, each containing impurities of a second conductivity type. However, the second conductive semiconductor layer may also have an undoped layer in which impurities are not intentionally doped. The first conductive semiconductor layer is, for example, an n-side semiconductor layer having a layer containing n-type impurities. The second conductive semiconductor layer is, for example, a p-side semiconductor layer having a layer containing p-type impurities. Hereinafter, the first conductive semiconductor layer will be referred to as the n-side semiconductor layer 202 and the second conductive semiconductor layer as the p-side semiconductor layer 204 in the explanation. In the example shown in the figure, the semiconductor laser element 100 has a substrate 201, an n-side semiconductor layer 202, an active layer 203, and a p-side semiconductor layer 204.The semiconductor laser element 100 may have an n-side electrode, a first electrode 205, a second electrode 206, an insulating film 207, and a mirror formed on the end face. However, in Figure 3, the n-side electrode is omitted from the illustration. In Figure 4, the n-side electrode, the first electrode 205, the second electrode 206, and the insulating film 207 are omitted from the illustration. The semiconductor laser element 100 is, for example, an end-face emitting laser element. The stacking direction of the semiconductor laser element 100 may be called downward, and the opposite direction may be called upward. The stacking direction of the semiconductor laser element 100 is the direction of the p-side semiconductor layer 204 with respect to the n-side semiconductor layer 202. The semiconductor laser element 100 is, for example, made of a nitride semiconductor, a phosphide semiconductor, or an arsenide semiconductor. The following explanation will take an example in which the semiconductor laser element 100 is a nitride semiconductor.

[0012] (Circuit board 201) The substrate 201 of the semiconductor laser element 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 by using a nitride semiconductor substrate, and its upper or lower 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 element 100 does not have to have a substrate 201. The upper or lower surface of the substrate may be an m plane, a plane, or 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 that is not intentionally doped with impurities. The undoped layer may contain, for example, Si as an n-type impurity, 1 × 10⁻⁶ 16 cm -3 The following applies, and if Ge is present as an n-type impurity, then 1 × 1017 cm -3 The following holds. The refractive index of the n-side clad layer 2021 is preferably smaller than the refractive index of the n-side guide layer 2022. Thereby, light is likely to be confined to the n-side guide layer 2022 side. The n-side clad layer 2021 is disposed between the active layer 203 and the substrate 201.

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

[0015] (Active layer 203) The active layer 203 is formed under 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 has one or more semiconductor layers containing p-type impurities. The p-side semiconductor layer 204 is formed below 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 that order from the substrate 201 side (i.e., from the active layer 203 side). The p-side semiconductor layer 204 does not necessarily have to include the p-side cladding layer 2042. The p-side semiconductor layer 204 may also include layers other than those mentioned above. The p-side semiconductor layer 204 may have an undoped layer that is not intentionally doped with impurities. It is preferable that the refractive index of the p-side cladding layer 2042 is smaller than the refractive index of the p-side guide layer 2041. This makes it easier for light 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) The semiconductor laser element 100 has a ridge 210 formed on its lower surface. The ridge 210 is provided, for example, on a part of the lower surface of the p-side semiconductor layer 204. In the example shown in the figure, the ridge 210 includes a first ridge 210a and a second ridge 210b. The first ridge 210a is provided on the portion that overlaps with the first portion 110 in a top view. The second ridge 210b is provided on the second portion 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 wider than that of the first ridge 210a. The width of the first ridge 210a is, for example, 80 μm to 120 μm. The width of the second ridge 210b is, for example, 300 μm to 400 μm. By having these lengths, light can be propagated in multiple transverse modes (i.e., transverse multimode), and the semiconductor laser element 100 can be made to have high output. The first ridge 210a is provided in continuity with the second ridge 210b, for example, such that its central axis in the guiding direction coincides with the optical axis of the second portion 120.

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

[0020] The material of the first 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] Furthermore, in a top view, the first electrode 205 is located below the core portion 115 and the diffraction grating 125. This allows the diffraction grating 125 to be made transparent while supplying current to the core portion 115 and causing laser oscillation. In the example shown in the figure, the first electrode 205 located below the core portion 115 and the first electrode 205 located below the diffraction grating 125 are integrally formed. That is, the first electrode 205 located below the core portion 115 and the first electrode 205 located below the diffraction grating 125 are not separated. This makes it easy to form the first electrode 205. Also, when the first electrode 205 is integrally formed, the path for supplying current to the core portion 115 and the diffraction grating 125 is common, and the voltage applied to the core portion 115 and the voltage applied to the diffraction grating 125 become equal. Since the core portion 115 is subjected to a voltage sufficient to cause the semiconductor laser element 10 to oscillate, the same voltage is also applied to the diffraction grating 125, resulting in a large amount of heat being generated by the diffraction grating 125. In this case, when viewed from above, the second portion 120 overlaps with the submount 310, allowing the diffraction grating 125 to dissipate heat effectively.

[0022] Furthermore, the second electrode 206 is located below the first electrode 205. This improves the bonding stability between the submount 310 and the semiconductor laser element 100 when bonding the second electrode 206 to the submount 310. The material of the second electrode 206 is, for example, the same as the material of the first electrode 205.

[0023] The insulating film 207 is provided below the first 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.

[0024] (Part 1 110) The first portion 110 is a portion having a front end surface 111. The first portion 110 is provided extending in a first direction which is the normal direction of the front end surface 111. The waveguide structure of the first portion 110 is a waveguide that propagates light, having a core portion 115 and cladding portions 116 located on both sides of the core portion 115 in a top view. The first portion 110 may propagate light along the longitudinal direction of the core portion 115 in multiple transverse modes (i.e., transverse multimodes). This makes it possible to increase the output power of the semiconductor laser element 100. The number of transverse modes is determined by the width of the core portion 115 and the difference between the refractive index of the core portion 115 and the refractive index of the cladding portion 116. The width of the core portion 115 is defined in a plane perpendicular to the optical axis of the waveguide and in a direction perpendicular to the stacking direction of the semiconductor laser element 100. Furthermore, the thickness of the core portion 115 is the thickness in the stacking direction of the semiconductor laser element 100 in a plane perpendicular to the optical axis of the waveguide.

[0025] In Embodiment 1, the core portion 115 overlaps with the first ridge 210a in a top view and is a portion set based on the width of the first ridge 210a, and includes at least an n-side semiconductor layer 202, an active layer 203, and a p-side semiconductor layer 204. The cladding portion 116 is a portion sandwiching the core portion 115 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 115 and the refractive index of the cladding portion 116 are equivalent refractive indices focusing on the height direction of each portion.

[0026] (Anti-reflective film 112) The anti-reflective coating 112 is provided on the front end surface 111, as shown in Figure 1, etc. The anti-reflective coating 112 may be formed from at least one selected from the group consisting of SiO2, Al2O3, Ta2O5, Nb2O5, TiO2, ZrO2, AlN, Si3N4, and GaN. The anti-reflective coating 112 may have a structure in which multiple different materials are arranged alternately, for example.

[0027] (Second part 120) The second section 120 is the section on which the diffraction grating 125 is provided. The second section 120 may be a slab waveguide. That is, in the second section 120, light confinement may be limited to the stacking direction only. Because the diffraction grating 125 is provided in the second section 120, which is a slab waveguide, the equivalent refractive index of the second section 120 becomes approximately the same even for different transverse modes, and the selected wavelengths (Bragg wavelengths) at the diffraction grating 125 are aligned.

[0028] (Diffraction grating 125) As shown in Figure 2, the diffraction grating 125 is provided in the second portion 120. In the semiconductor laser element 100 of Embodiment 1, in a top view, the width of the diffraction grating 125 in the second direction perpendicular to the first direction is greater than the width of the core portion 115. This structure reduces the variation in the oscillation wavelength of light incident from the core portion 115 to the diffraction grating 125. In particular, when the first portion 110 is a structure that propagates laser light in multiple transverse modes, the fact that the width of the diffraction grating 125 is greater than the width of the core portion 115 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 125.

[0029] The distance between the two ends of the diffraction grating 125 is, for example, 1.5 to 100 times the width of the core portion 115, and more preferably 3 to 10 times. That is, if the width of the core portion 115 is, for example, 15 μm to 100 μm, then the distance between the two ends of the diffraction grating 125 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 125 may be constant, or it may be increased from the first portion 110 side toward the rear end surface 121 of the second portion 120. The diffraction grating 125 can be formed by alternately (periodically) providing members with different refractive indices in the direction of light propagation.

[0030] The width of the diffraction grating 125 in the second direction is constant across the first direction and is set to be larger than the beam diameter of the laser beam at the rear end surface 121. As a result, the equivalent refractive index is approximately the same for different transverse modes in the diffraction grating 125, and the selected wavelengths (Bragg wavelengths) in the diffraction grating 125 are aligned. The beam diameter of the laser beam is defined, for example, by D4σ (second moment width).

[0031] The diffraction grating 125 may be provided, for example, between two adjacent semiconductor layers in the vertical direction, on the p-side semiconductor layer 204, or on the n-side semiconductor layer 202. In the example shown in the figure, the diffraction grating 125 is provided, for example, between the n-side cladding layer 2021 and the n-side guide layer 2022. Specifically, the diffraction grating 125 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 125 can be appropriately selected considering the wavelength of light emitted by the active layer 203. The period of the diffraction grating 125 may be, for example, 60 nm to 400 nm, preferably 70 nm to 300 nm. In the example shown in the figure, the diffraction grating 125 is formed from periodic convex and concave portions, and the shape of the boundary between the convex and concave portions is linear when viewed from above.

[0032] Wavelength enhanced by diffraction grating 125 (Bragg wavelength λ) B The relationship expressed in Equation 1 below holds between the period Λ of the diffraction grating 125 and the equivalent refractive index n of the second part 120. Note that the equivalent refractive index of the second part 120 refers to the effective refractive index obtained by considering the optical confinement in the stacking direction of the semiconductor laser element 100 and further averaging the modulation component of the refractive index of the diffraction grating.

[0033] λ B =2×Λ×n (Equation 1)

[0034] In other words, the Bragg wavelength can be determined by the period Λ of the diffraction grating 125 and the equivalent refractive index n of the second part 120. The Bragg wavelength can be adjusted by adjusting the period of the diffraction grating 125 to an arbitrary value. The period of the diffraction grating 125 can be appropriately selected considering the wavelength of light emitted by the active layer 203.

[0035] Furthermore, the equivalent refractive index n of the second part 120 is approximately the same for each transverse mode, and therefore the Bragg wavelength λ corresponding to each transverse mode is approximately the same. B This is almost the same. As a result, the full width at half maximum of the oscillation wavelength of the laser light emitted by the semiconductor laser element 100 becomes smaller. For example, the full width at half maximum of the oscillation wavelength of the laser light emitted by the semiconductor laser element 100 is between 0.01 nm and 0.5 nm.

[0036] (Reflective film 126) The reflective film 126 is provided on the rear end surface 121, as shown in Figure 2, etc. In the example shown in the figure, the diffraction grating 125 includes the rear end surface 121. Therefore, the reflective film 126 is provided in contact with the diffraction grating 125. The reflective film 126 is, for example, a reflective film or a protective film. The reflective film 126 can be formed from, for example, at least one selected from the group consisting of SiO2, Al2O3, Ta2O5, Nb2O5, TiO2, ZrO2, AlN, Si3N4, and GaN. The reflective film 126 may have a structure in which multiple different materials are arranged alternately, for example. In the example shown in the figure, the reflective film 126 overlaps with the submount 310 in a top view. This improves the heat dissipation of the reflective film 126.

[0037] (Light-emitting device 10) As shown in Figures 6 and 7, the light-emitting device 10 includes a semiconductor laser element 100 and a submount 310. The semiconductor laser element 100 is positioned on the upper surface of the submount 310. This allows for efficient heat dissipation of the semiconductor laser element 100 while increasing the height of the emission end face of the semiconductor laser element 100. Furthermore, in a top view, the front end face 111 of the semiconductor laser element 100 is positioned so as not to overlap with the submount 310. That is, the front end portion of the semiconductor laser element 100, including the front end face 111, is provided to protrude from the submount 310. This reduces the possibility of stray light occurring when light emitted from the front end face 111 strikes the upper surface of the submount 310.

[0038] As mentioned above, extending the front end surface 111 from the submount 310 is effective in preventing stray light. However, the portion that protrudes from the submount 310 does not overlap with the submount 310 when viewed from above. Of the semiconductor laser element 100, the portion that does not overlap with the submount 310 when viewed from above has reduced heat dissipation compared to the overlapping portion.

[0039] The diffraction grating 125 can transmit light when an electric current is applied, but unlike the core portion 115, the current applied to the diffraction grating 125 is not converted into light but into heat. Therefore, the diffraction grating 125 generates a large amount of heat. If, contrary to this disclosure, the diffraction grating is provided at the front end of the submount, at least a part of the diffraction grating and the submount will not overlap in a top view, which may result in insufficient heat dissipation from the diffraction grating. In that case, the diffraction grating 125 may not dissipate heat sufficiently, potentially leading to a decrease in power conversion efficiency.

[0040] Furthermore, the refractive index of the diffraction grating 125 changes due to heat generation, and as a result, the selectable wavelength by the diffraction grating 125 may change, as can be seen from Equation 1. If, contrary to this disclosure, the diffraction grating is provided at the front end of the submount, at least a portion of the diffraction grating and the submount will not overlap in a top view, and the heat dissipation of the diffraction grating may be insufficient. In that case, the wavelength of the light emitted from the semiconductor laser element may deviate from the desired value.

[0041] In this disclosure, in a top view, the front end surface 111 of the semiconductor laser element 100 does not overlap with the submount 310, while the second portion 120 of the semiconductor laser element 100 overlaps with the submount 310. That is, in a top view, the diffraction grating 125 overlaps with the submount 310. This allows for effective heat dissipation of the diffraction grating while achieving the effect of stray light suppression. As a result, the power conversion efficiency of the semiconductor laser element 100 can be improved. Furthermore, the selected wavelength of the diffraction grating 125 is stabilized, and a light-emitting device 10 can be obtained in which the wavelength of light emitted from the semiconductor laser element 100 is a desired value.

[0042] In the example shown in the figure, the diffraction grating 125 is provided on the n-side semiconductor layer 202. This makes it easier to provide the diffraction grating 125. Also, when the diffraction grating 125 is provided on the n-side semiconductor layer 202, it tends to generate more heat compared to when it is provided on the p-side semiconductor layer 204. In this case, when viewed from above, the second portion 120 overlaps with the submount 310, allowing the diffraction grating 125 to dissipate heat effectively. However, the diffraction grating 125 may also be provided on the p-side semiconductor layer 204. This can improve the output of the semiconductor laser element 100.

[0043] Furthermore, the semiconductor laser element 100 is positioned on the submount 310 on the side of the p-side semiconductor layer 204 relative to the active layer 203. This allows the second electrode 206 to be used for bonding between the semiconductor laser element 100 and the submount 310, improving bonding stability. In addition, the active layer 203 can be brought closer to the submount 310, improving the heat dissipation of the semiconductor laser element 100.

[0044] (Submount 310) 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, graphite, 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 element 100 during operation.

[0045] 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 element 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.

[0046] (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 from, for example, a metal as the main material. As the metal, for example, Cu or a Cu-containing alloy can be used. 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.

[0047] 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 element 100.

[0048] 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.

[0049] 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.

[0050] The reflective member 360 is a component that reflects light emitted from the semiconductor laser element 100 and changes the direction of light propagation. In the example shown in the figure, the reflective member 360 reflects the light emitted from the semiconductor laser element 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 example shown in the figure, 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.

[0051] 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.

[0052] The wire 370 is a component for supplying current to the semiconductor laser element 100. In the example shown in the figure, the wire 370 electrically connects the upper surface of the stepped portion 353 to the upper surface of the semiconductor laser element 100 or the submount 310. Examples of materials for the wire 370 include Au, Ag, Cu, Al, and W.

[0053] 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 example shown in the figure, 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 element 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 element 100 inside the airtight space, the semiconductor laser element 100 can be protected from contamination.

[0054] (Variation 1) Next, with reference to Figure 8, the semiconductor laser element 200 according to Modification 1 will be described. The semiconductor laser element 200 according to Modification 1 differs from the semiconductor laser element 100 according to Embodiment 1 in that the shape of the periodic convex and concave portions of the diffraction grating 125 is arc-shaped.

[0055] Figure 8 is a schematic diagram showing the waveguide structure of a semiconductor laser element 200 according to Modification 1 of this disclosure. Figure 9 is an enlarged view of a part of the diffraction grating in Figure 8. The individual components of the semiconductor laser element 200 will be described below. Content that overlaps with Embodiment 1 will be omitted as appropriate.

[0056] As shown in Figure 8, in the semiconductor laser element 200, the diffraction grating 125 is formed from periodic convex and concave portions, and the shape of the boundary between the convex and concave portions is curved when viewed from above. In the example shown in the figure, the shape of the boundary between the convex and concave portions is arc-shaped. Laser light emitted from the first portion 110 to the second portion 120 propagates through the second portion 120 at a maximum diffusion angle Θmax determined by the refractive index of the core portion 115, the refractive index of the cladding portion 116, and the refractive index of the second portion 120. The maximum diffusion angle Θmax is also called the maximum reception angle. As shown in Figure 9, because the shape of the diffraction grating 125 is arc-shaped, light propagating inside the diffraction grating 125 at the maximum diffusion angle Θmax is incident perpendicularly to the boundary between the convex and concave portions of the diffraction grating 125. As a result, the proportion of light returning from the diffraction grating 125 to the core portion 115 increases, and light loss is reduced.

[0057] (Modification 2) Next, with reference to Figure 10, a semiconductor laser element 300 according to Modification 2 will be described. The semiconductor laser element 300 according to Modification 2 differs from the semiconductor laser element 100 according to Embodiment 1 in that the shape of the periodic convex and concave portions of the diffraction grating 125 is bent.

[0058] Figure 10 is a schematic diagram showing the waveguide structure of a semiconductor laser element according to Modification 2 of this disclosure. Figure 11 is an enlarged view of a part of the diffraction grating in Figure 10. The individual components of the semiconductor laser element 300 will be described below. Content that overlaps with Embodiment 1 will be omitted as appropriate.

[0059] As shown in Figure 10, in the semiconductor laser element 300, the diffraction grating 125 is formed from periodic convex and concave portions, and the shape of the boundary between the convex and concave portions is curved when viewed from above. In the example shown in the figure, the shape of the boundary between the convex and concave portions is bent. Laser light emitted from the first portion 110 to the second portion 120 propagates through the second portion 120 at a maximum diffusion angle Θmax determined by the refractive index of the core portion 115, the refractive index of the cladding portion 116, and the refractive index of the second portion 120. As shown in Figure 11, because the shape of the diffraction grating 125 is bent, light propagating inside the diffraction grating 125 at a maximum diffusion angle Θmax is incident perpendicularly to the boundary between the convex and concave portions of the diffraction grating 125. As a result, the proportion of light returning from the diffraction grating 125 to the core portion 115 increases, and light loss is reduced.

[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 element having an active layer, a semiconductor laminate having a waveguide structure, and a front end surface, The aforementioned semiconductor stacked portion is (i) A first portion that includes the front end surface and, in a top view, has a core portion and cladding portions provided on both sides of the core portion, and extends in a first direction which is the normal direction to the front end surface, (ii) A second portion including a diffraction grating, wherein, in a top view, the width of the diffraction grating in a second direction perpendicular to the first direction is greater than that of the core portion, A semiconductor laser element, The semiconductor laser element is arranged in a submount, A light-emitting device in which, when viewed from above, the front end surface of the semiconductor laser element does not overlap with the submount, and the second portion of the semiconductor laser element overlaps with the submount. (Section 2) The light-emitting device according to item 1, wherein the semiconductor laser element propagates laser light in multiple transverse modes. (Section 3) The light-emitting device according to claim 1 or 2, wherein the second part has a rear end surface, and a reflective film is provided on the rear end surface. (Section 4) The light-emitting device according to any one of items 1 to 3, further comprising a first electrode, wherein the first electrode is provided below the core portion and the diffraction grating. (Section 5) The light-emitting device according to item 4, wherein the first electrode provided at the lower part of the core portion and the first electrode provided at the lower part of the diffraction grating are integrally formed. (Section 6) The light-emitting device according to item 4 or 5, further comprising a second electrode, the second electrode being located below the first electrode. (Section 7) The light-emitting device according to any one of claims 1 to 6, wherein the semiconductor stack further includes a first conductive semiconductor layer and a second conductive semiconductor layer provided on the opposite side of the active layer from the first conductive semiconductor layer, and the diffraction grating is provided on the side of the first conductive semiconductor layer. (Section 8) The light-emitting device according to item 7, wherein the semiconductor laser element is arranged on the submount on the second conductive semiconductor layer side. (Section 9) The light-emitting device according to any one of claims 1 to 8, wherein the diffraction grating is formed from periodic convex portions and concave portions, and the shape of the boundary between the convex portions and concave portions is curved when viewed from above. (Section 10) The light-emitting device according to any one of claims 1 to 9, wherein the width of the diffraction grating in the second direction is constant over the first direction and is set to be larger than the beam diameter of the laser light at the rear end face. [Explanation of Symbols]

[0062] 10 Light-emitting device 100, 200, 300 semiconductor laser elements 110 Part 1 111 Front end surface 115 Core section 116 Clad section 120 Part 2 121 Rear end surface 125 Diffraction grating 126 Reflective film 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 205 1st electrode 206 2nd electrode 207 Insulating film 210 Ridge 210a First Ridge 210b Second Ridge 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

Claims

1. A semiconductor laser element having an active layer, a semiconductor laminate having a waveguide structure, and a front end surface, The aforementioned semiconductor stacked portion is (i) A first portion that includes the front end surface and, in a top view, has a core portion and cladding portions provided on both sides of the core portion, and extends in a first direction which is the normal direction to the front end surface, (ii) A second portion including a diffraction grating, wherein, in a top view, the width of the diffraction grating in a second direction perpendicular to the first direction is greater than that of the core portion, A semiconductor laser element, The semiconductor laser element is arranged in a submount, A light-emitting device in which, when viewed from above, the front end surface of the semiconductor laser element does not overlap with the submount, and the second portion of the semiconductor laser element overlaps with the submount.

2. The light-emitting device according to claim 1, wherein the semiconductor laser element propagates laser light in multiple transverse modes.

3. The light-emitting device according to claim 1, wherein the second part has a rear end surface, and a reflective film is provided on the rear end surface.

4. The light-emitting device according to claim 1, further comprising a first electrode, the first electrode being provided below the core portion and the diffraction grating.

5. The light-emitting device according to claim 4, wherein the first electrode provided at the lower part of the core portion and the first electrode provided at the lower part of the diffraction grating are integrally formed.

6. The light-emitting device according to claim 1, wherein the semiconductor stack further includes a first conductive semiconductor layer and a second conductive semiconductor layer provided on the opposite side of the active layer from the first conductive semiconductor layer, and the diffraction grating is provided on the side of the first conductive semiconductor layer.

7. The light-emitting device according to claim 6, wherein the semiconductor laser element is arranged on the submount on the second conductive semiconductor layer side.

8. The light-emitting device according to claim 4, further comprising a second electrode, the second electrode being located below the first electrode.

9. The light-emitting device according to claim 1, wherein the diffraction grating is formed from periodic convex portions and concave portions, and the shape of the boundary between the convex portions and concave portions is curved when viewed from above.

10. The light-emitting device according to claim 3, wherein the width of the diffraction grating in the second direction is constant over the first direction and is set to be larger than the beam diameter of the laser light at the rear end face.

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