SEMICONDUCTOR LASER ELEMENT

Abstract

A semiconductor laser element comprises a semiconductor multilayer region containing an active layer, wherein the semiconductor multilayer region includes (i) a first region comprising a diffraction grating, and (ii) a second region configured to cause laser light to propagate in multiple transverse modes within the second region, the second region comprising a core region and cladding regions provided on two opposite sides of the core region; at least one electrode arranged on the semiconductor multilayer region; and a current shielding structure. The semiconductor laser element has a waveguide structure. In a plan view, the first region includes a central region where light entering from the second region propagates, and a peripheral region located outside the central region.In a top view, the current shielding structure is located in a position that at least partially overlaps the peripheral region.

Description

CROSS REFERENCE TO RELATED APPLICATIONSThis application claims priority to Japanese Patent Application No. 2023-175306 filed on Oct. 10, 2023 and Japanese Patent Application No. 2024-159383 filed on Sep. 13, 2024. The disclosures of these applications are hereby incorporated by reference in their entirety.BACKGROUNDTechnical FieldThe present disclosure relates to a semiconductor laser element.Prior ArtIn recent years, there has been a demand for higher power of laser light from a semiconductor laser element. A semiconductor laser element with high power has been used as a light source for processing, for example. For example, Japanese Patent Application Publication No. 2011-151238 discloses a multitransversal mode laser in which optical damage on the stripe side can be prevented.SUMMARYThe semiconductor laser element disclosed in Japanese Patent Application Publication No. 2011-151238 has insufficient power conversion efficiency and has room for improvement.An object of the present disclosure is to provide a semiconductor laser element having high power conversion efficiency.A semiconductor laser element according to an embodiment of the present disclosure includes: a semiconductor multilayer region including an active layer, the semiconductor multilayer region including (i) a first region including a diffraction grating and (ii) a second region configured to cause laser light to propagate in multiple transverse modes in the second region, the second region including a core region and cladding regions provided on two opposite sides of the core region; at least one electrode disposed on the semiconductor multilayer region; and a current shielding structure. The semiconductor laser element has a waveguide structure. In a plan view, the first region includes a central region where light entering from the second region propagates and a peripheral region located outside the central region. In a plan view, the current shielding structure is located at a position that at least partially overlaps the peripheral region.As the semiconductor laser element according to an embodiment of the present disclosure, a semiconductor laser element having high power conversion efficiency can be provided.BRIEF DESCRIPTION OF DRAWINGSFIG. 1 is a plan view of a semiconductor laser element of a first embodiment according to the present disclosure. FIG. 2 is a schematic plan view of the region structure of the semiconductor laser element according to the first embodiment. FIG. 3 is a schematic cross-sectional view taken along line III-III of the semiconductor laser element illustrated in FIG. 1. FIG. 4 is a schematic cross-sectional view taken along line IV-IV of the semiconductor laser element illustrated in FIG. 1. FIG. 5 is a diagram illustrating an overview of a method for measuring a beam waist radius W 0 and a beam divergence angle φ. FIG. 6 is a schematic cross-sectional view of a first region of a semiconductor laser element of a second embodiment according to the present disclosure. FIG. 7 is a schematic cross-sectional view of a first region of a semiconductor laser element of a third embodiment according to the present disclosure. FIG. 8 is a schematic cross-sectional view of a first region of a semiconductor laser element of a fourth embodiment according to the present disclosure. FIG. 9 is a schematic plan view of another example of the semiconductor laser element of the first embodiment.DETAILED DESCRIPTIONEmbodiments, modified examples, and examples for implementing the invention according to the present disclosure will be described below with reference to the accompanying drawings. A semiconductor laser element according to the present disclosure described below is intended to embody the technical ideas behind the invention according to the present disclosure, and the invention according to the present disclosure is not limited to the following description unless specifically stated otherwise.In each drawing, components having identical functions may be denoted by the same reference numerals. In view of the simplicity of explanation or understanding of the gist of the invention, the embodiments, modified examples, or examples may be separately illustrated for the sake of simplicity, but partial substitutions or combinations of the configurations illustrated in various embodiments, modified examples, and examples are possible. In the embodiments, modified examples, and examples described below, descriptions of items that are the same as those already described are omitted, and only different points will be described. In particular, similar effects and effects starting from similar configurations are not mentioned in each of the embodiment, the modified example, and the example. The size, positional relationship, and the like of components illustrated in the drawings may be exaggerated for clarity.First EmbodimentA semiconductor laser element L1 according to the first embodiment includes an active layer 120 and a semiconductor multilayered region 101 having the waveguide structure shown in FIG. 2. FIG. 1 is a schematic plan view illustrating the semiconductor laser element L 1 of the present embodiment in a plan view.Specifically, as illustrated in FIGS. 1 to 4, the semiconductor multilayer region 101 of the semiconductor laser element L 1 according to the first embodiment includes: (i) a first region 1 including a diffraction grating 105, and (ii) a second region 2 including a core region 21 and cladding regions 22 provided on two opposite sides of the core region 21, the second region 2 being configured to cause laser light to propagate in multiple transverse modes in the second region 2.In the semiconductor laser element L 1 of the first embodiment, the first region 1 includes, in a plan view, a central region 11 configured to cause light entering from the second region to propagate in the central region 11 and a peripheral region 12 located outside the central region 11. A current shielding structure 10 is provided at a position at least partially overlapping the peripheral region 12.Furthermore, the core region has a refractive index n 21 the cladding regions have a refractive index n 22 and the central region has a refractive index n 1.In the semiconductor laser element L 1 including the first region 1 and the second region 2 configured as described above, laser light emitted from the second region 2 propagates through the first region 1 at a maximum scattering angle θ max1 determined by the refractive indices n 1, n 21 and n 22.In the semiconductor laser element L 1 according to the first embodiment, the current shielding structure 10 is formed of an insulating film 140 disposed on the semiconductor multilayer region 101 in the first region 1, as will be described later. The semiconductor laser element L1 is, for example, a multitransversal mode type semiconductor laser element. When the semiconductor laser element is a multi-transverse mode semiconductor laser element, the effect of improving light emission efficiency caused by reduction of heat generation due to a reactive current in a region that does not contribute to oscillation (propagation of light) can be further obtained as compared with a single-transverse mode semiconductor laser element.The semiconductor laser element L 1 of the first embodiment configured as described above can increase the light emission output with respect to power consumption and efficiently obtain high-power light.The reasons will be described below.First, in the semiconductor laser element including the diffraction grating 105 in the first region 1 and including the waveguide structure in the second region 2, for example, light emitted by introducing a current into the core region 21 of the second region 2 propagates through the waveguide including the core region 21, is incident on the first region 1, and is then reflected at the diffraction grating 105 in the first region 1 to return to the second region 2, and the returned light is amplified. This is repeated to cause laser oscillation.In the semiconductor laser element L 1 according to the first embodiment, in order to perform more effective laser oscillation, coating may be applied to an end surface of the first region 1 on a side opposite to a side on which the second region 2 is located and to an end surface of the second region 2 on a side opposite to a side on which the first region 1 is located. The semiconductor laser element L 1 may include an antireflection (AR) coating provided on the end surface of the first region 1 on the side opposite to the side on which the second region 2 is located, and a high reflection (HR) coating provided on the end surface of the second region 2 on the side opposite to the side on which the first region 1 is located.As described above, the laser light incident on the first region 1 including the central region 11 having the refractive index n 1 and emitted from the second region 2 propagates through the first region 1 at the maximum scattering angle θ max1 determined by the refractive index n 1, the refractive index n 21 and the refractive index n 22. In view of this, it is preferable to set the width of the region in the first region 1 where the current is introduced into the first region 1 to be wider than the width of the region in the second region 2 where the current is introduced. This is because the region of the first region 1 where the current is introduced functions as the diffraction grating 105. Thus, the light propagating through the first region 1 while expanding at the maximum scattering angle θ max1 can be reflected at the diffraction grating 105.However, the inventors of the present application have found that although a certain effect of increasing the light emission efficiency is obtained by setting the width of the region in the first region 1 where the current is introduced wider than the width of the region in the second region 2 where the current is introduced, the light emission efficiency decreases when the width of the region in the first region 1 where the current is introduced is further excessively increased.In the first region 1, a region that does not contribute to oscillation (propagation of light) corresponds to a region outside an imaginary line extending from two opposite ends of the emission end surface of the core region 21 at the maximum scattering angle θ max1.Thus, in the semiconductor laser element according to this embodiment, the current shielding structure 10 is provided in at least a part of the peripheral region 12 including the region outside the imaginary line extending from two opposite ends of the emission end surface of the core region 21 at the maximum scattering angle θ max1 to reduce the reactive current.In the semiconductor laser element L 1 according to the first embodiment, the central region 11 is the region including a region within the imaginary lines extending from two opposite ends of the emission end surface of the core region 21 at the maximum scattering angle θ max1. Moreover, for example, a region outside the imaginary lines extending from two opposite ends of the emission end surface of the core region 21 at the maximum scattering angle θ max1 may be defined as the peripheral region 12. Moreover, for example, a region within the imaginary lines extending from two opposite ends of the emission end surface of the core region 21 at the maximum scattering angle θ max1 may be defined as the central region 11. By setting the central region 11 as the region including a region within the imaginary lines extending from two opposite ends of the emission end surface of the core region 21 at the maximum scattering angle θ max1 it is possible to efficiently introduce a current into the region where light propagates while reducing the reactive current to a region that does not contribute to light propagation.In this specification, the refractive index n 21 and the refractive index n 22 refer to effective refractive indices in consideration of the optical confinement in the lamination direction of the semiconductor multilayer region 101 and may be referred to as an equivalent refractive index. The refractive index n 1 refers to an effective refractive index for which optical confinement in the lamination direction of the semiconductor multilayer region 101 is taken into account and variation in the refractive index of the diffraction grating 105 is averaged. The maximum scattering angle θ max1 is equal to the maximum light receiving angle of the optical waveguide in the second region 2.Hereinafter, the semiconductor laser element L 1 according to the first embodiment will be described in detail with reference to the drawings.FIG. 1 is a plan view of the semiconductor laser element L 1 according to the first embodiment. FIG. 2 is a schematic plan view of the region structure of the semiconductor laser element L 1 according to the first embodiment. FIG. 3 is a schematic cross-sectional view taken along the line III-III of the semiconductor laser element L 1 illustrated in FIG. 1. FIG. 4 is a schematic cross-sectional view taken along line IV-IV of the semiconductor laser element L 1 illustrated in FIG. 1.The semiconductor laser element L 1 according to the first embodiment includes the semiconductor multilayer region 101 provided on a substrate 100. As illustrated in FIGS. 3 and 4, the semiconductor multilayer region 101 includes, for example: (a) an n-side semiconductor layer 110 including an n-side cladding layer 111 and an n-side optical guide layer 112; (b) the active layer 120 located on the n-side semiconductor layer 110; and (c) a p-side semiconductor layer 130 located on the active layer 120 and including a p-side optical guide layer 131, a p-side cladding layer 132, and a p-side contact layer 133.The semiconductor multilayer region 101 includes, for example, a ridge 135 provided in the p-side contact layer 133 and the p-side cladding layer 132. The burr 135 includes a first burr 135 aprovided in the first region 1 and a second burr 135 bprovided in the second region 2. In a plan view, the first ridge 135 aand the second ridge 135 bare provided such that center lines thereof in a traveling direction of the laser light coincide with each other, for example.In FIG. 1, the outer lateral surface of the first burr 135 aand the outer lateral surface of the second burr 135 bare illustrated to coincide with the outer lateral surface of a second electrode 152 described later, and accordingly, the first burr 135 aand the second burr 135 bare indicated by broken lines drawn from the outer lateral surfaces of the first burr 135 aand the second burr 135 bin FIG. 1.As described above, since the light emitted from the second region 2 and incident on the first region 1 expands and propagates in the first region 1, the first ridge 135 ais set wider than the second ridge 135 b.In addition, the outer lateral surface of the first region 1 and the outer lateral surface of the first ridge 135 aare located close to each other, and the refractive index n 1 of the central region 11 is not varied in the light propagating direction and the width direction and is constant in these directions.In this specification, the width direction refers to a direction orthogonal to both the light propagating direction and the laminating direction of the semiconductor multilayer region 101.On the semiconductor multilayer region 101, a p-electrode 150 is disposed in contact with the upper surface of the fin 135. The p-electrode 150 includes a first electrode 151 and the second electrode 152. The first electrode 151 is disposed in contact with the p-side contact layer 133, the first electrode 151 and the second electrode 152 are connected to each other via an opening portion of an insulating film that shields current, as described later. That is, in the first embodiment, the current shielding structure 10 is formed by the insulating film 140 disposed at a position at least partially overlapping the peripheral region 12.Specifically, the first electrode 151 is first disposed in contact with, for example, the entire upper surface of the p-side layer 133 on the fin 135 of the semiconductor multilayer region 101. The insulating film 140 is disposed on the first electrode 151. The insulating film 140 includes a first opening portion 140 alocated on the first fin 135 aand a second opening portion 140 blocated on the second fin 135 b. The first opening portion 140 aand the second opening portion 140 bare continuous with each other, for example, and the center axes of the first opening portion 140 aand the second opening portion 140 bcoincides with the center lines of the first ridge 135 aand the second ridge 135 bin the advancing direction of the laser light, for example. In view of the fact that the light entering the first region 1 from the second region 2 expands and propagates in the first region 1, the first opening area 140 ais preferably wider than the second opening area 140 bsuch that the current introduction region in the first region 1 is, for example, wider than the current introduction region in the second region 2 to increase the light emission efficiency. However, as described above, when the width of the region in the first region 1 where the current is introduced is excessively increased, heat due to reactive current or the like may be generated outside the waveguide region, such that the efficiency may be reduced. In view of this, the first opening portion 140 ais set to be wider than the second opening portion 140 b, so that heat generation due to reactive current or the like outside the waveguide region, in other words, the peripheral region 12, can be effectively reduced. It is preferable that the width of the first opening portion 140 acoincides with the imaginary lines extending from two opposite ends of the emission end surface of the core portion 21 at the maximum scattering angle θ max1. With this configuration, heat generation due to a reactive current or the like in the peripheral region 12 can be effectively reduced.In this specification, the term "opening area" does not indicate only a region surrounded by four sides. For example, a region located between two insulating films may be referred to as an opening area in the insulating film.In the first embodiment, the second electrode 152 is disposed so as to cover the first opening portion 140 aand the second opening portion 140 b, and the second electrode 152 is connected to the first electrode 151 via the first opening portion 140 aand the second opening portion 140 b. In other words, the current is introduced into the second region 2 via the second opening portion 140 b. In the first embodiment, as illustrated in FIG. 4, in the second region 2, the width of the second opening portion 140 bis set to be substantially equal to the width of the second ridge 135 b. On the other hand, in the first region 1, when the width of the current introduction region is excessively increased, there is a possibility that the efficiency due to heat generation by a reactive current or the like on the outer side of the waveguide region is lowered. Thus, the insulating film 140 is arranged to at least partially overlap the peripheral region 12 to form the current shielding structure 10. Specifically, in the first region 1, the width of the region where the second electrode 152 and the first electrode 151 are in contact with each other is limited to the width of the first opening region 140 avia the insulating film 140. This structure shields the current in the peripheral region 12. That is, the current is introduced from a region where the insulating film 140 is not provided. For example, the first electrode 151 is formed on the entire upper surface of the p-side contact layer 133, and this structure may cause the current introduced from the second electrode 152 to expand in the width direction at the first electrode 151 and be introduced into the p-side contact layer 133. Thus, in the first embodiment, the first electrode 151 is preferably configured to reduce the expansion of the current in the width direction. For example, in the first embodiment, the first electrode 151 is preferably formed thin to reduce the widthwise expansion of the current. For example, the thickness of the first electrode 151 in the lamination direction of the semiconductor multilayer region 101 is preferably in a range of 0.05 μm to 2 μm. The first electrode 151 may be made of indium tin oxide (ITO) to reduce the spread of the current in the width direction. Thus, heat generation due to a reactive current or the like outside the waveguide region can be reduced. As described above, the range in which the current flowing to the p-side contact layer 133 is shielded in the first embodiment is determined by parameters including the width of the first opening portion 140 ain the insulating film 140, the resistance value and the thickness of the first electrode 151, and the like. The current is introduced into the second region 2 via the second opening portion 140 b, which allows the core region 21 and the cladding regions 22 to be provided on both sides of the core region 21 in the second region 2, which allows the light to oscillate in a multitransversal mode corresponding to the width of the second opening portion 140 b. In other words, it is preferable to appropriately adjust parameters including the width of the first opening portion 140 aprovided in the insulating film 140, the resistance and the thickness of the first electrode 151, and the like, so that heat generation due to a reactive current or the like in the peripheral region 12 can be effectively reduced. For example, the width of the first opening portion 140 ais preferably 90% or less, and more preferably 40% or less, of the width of the first region 1 under the condition that the insulating film 140 does not reach the region within the imaginary lines expanding at the maximum scattering angle θ max1. With this configuration, it is possible to effectively reduce the reactive current to the peripheral region 12. The resistance value of the first electrode 151 may be set in a range of 300 μΩ to 2600 μΩ, for example.In the semiconductor laser element L 1 according to the first embodiment, the width of the ridge 135 is set as follows such that the laser light propagates in desired plural transverse modes.First, the second region 2 includes the core region 21 having the refractive index n 21 and the cladding regions 22 having the refractive index n 22 located on two opposite sides of the core region 21. Moreover, the second fin 135 bis provided in the central region of the p-side semiconductor layer 130 of the second region 2 at a predetermined interval from both lateral surfaces of the second region 2. Thus, in the second region 2, the core region 21 having the refractive index n 21 is formed below the second ridge 135 b, and the cladding regions 22 having the refractive index n 22 are formed on two opposite sides of the core region 21, thereby forming the waveguide structure of the second region 2. In the semiconductor laser element L 1 according to the first embodiment, the width of the core region 21, in other words, the width of the second ridge 135 bis set such that the laser light including the desired multiple transverse modes propagates. The first electrode 151 is preferably disposed in contact with the upper surface of the second ridge side 135 bwithout being in contact with the upper surface of the p-side cladding layer 132 on two opposite sides of the second ridge side 135 b. With such a configuration, it is possible to reduce the current flow through the cladding regions 22.While in the first embodiment, the core region 21 and the cladding regions 22 are formed on two opposite sides of the core region 21 in a plan view by providing the second ridge 135 b, the core region 21 and the cladding regions 22 may also be formed without forming the second ridge 135 b, for example, by making the current introduction region of the second region 2 narrower in width than the entire second region 2.In contrast, the first region 1 is not a region in which the light entering from the second region 2 and propagating while expanding at the maximum scattering angle θ max1 is included in a specific waveguide (core region 21) and propagates. Further, the first ridge 135 ais not an essential component in the first region 1 as long as the light incident from the second region 2 can propagate while expanding at the maximum scattering angle θ max1. For example, a portion of the semiconductor multilayer region 101 without the second region 2 may be the first region 1 without forming the first fin 135 a. For example, when the first region 1 includes the first ridge 135 a, as illustrated in FIG. 3, two opposing lateral surfaces of the first ridge 135 amay be located close to two opposing lateral surfaces of the first region 1. The width of the semiconductor multilayer region 101 constituting the first region 1 and the width of the first ridge 135 awhen including the first ridge 135 aare set such that the equivalent refractive indices with respect to the plurality of transverse modes of the laser light incident from the second region 2 into the first region 1 are substantially the same, and the maximum scattering angle θ max1 of the laser light emitted from the second region 2 and entering the first region 1 is taken into consideration such that the propagating light does not exit from the lateral surfaces of the semiconductor multilayer region 101.Specifically, in a cross section orthogonal to the optical axis of the laser light, two opposite end portions of the first region 1 in the direction orthogonal to the laminating direction of the semiconductor multilayer region 101 are arranged outside the imaginary lines propagating from two opposite ends of the emission end surface of the core region 21 on the first region 1 side at the maximum scattering angle θ max1.The diffraction grating 105 is located in the first region 1. The diffraction grating 105 is provided such that, for example, two opposite ends of the diffraction grating 105 extend to two opposite end regions of the first region 1.The cross-sectional shape of the burr 135 may be a rectangular shape having a constant width as illustrated in FIGS. 3 and 4, or may be, for example, a trapezoidal shape in which the width decreases as the distance from the substrate 100 increases, or an inverse trapezoidal shape in which the width increases as the distance from the substrate 100 increases.In the semiconductor laser element L 1 according to the first embodiment of the present disclosure configured as described above, the width of the waveguide in the second region 2 is set to allow laser oscillation including desired plural transverse modes, and the current shielding structure 10 is provided in the first region 1.Thus, in the semiconductor laser of the first embodiment, laser light can be oscillated and propagated in a plurality of transverse modes, so that it is possible to provide a semiconductor laser element L 1 that can achieve high power conversion efficiency.Hereinafter, components of the semiconductor laser element L 1 according to the first embodiment will be described in detail with specific examples.The semiconductor laser element L 1 according to the first embodiment is not limited to the following specific examples, and is sufficient to have a basic configuration that can obtain the above-described effects.Substrate 100The substrate 100 of the semiconductor laser element L 1 according to the first embodiment is, for example, a semiconductor substrate. The substrate 100 is, for example, a nitride semiconductor substrate such as a GaN substrate. The nitride semiconductor substrate may contain an n-type impurity. An element serving as the n-type impurity may be, for example, O, Si, or Ge.The nitride semiconductor substrate may be used as the substrate 100, and an upper surface thereof may be a +c plane (i.e., a (0001) plane). In the first embodiment, the c-plane is not limited to a plane exactly coincident with the (0001) plane, but includes a plane having a off angle of ±1 degree or less, preferably ±0.03 degrees or less. The semiconductor laser element L 1 may not include the substrate 100. As the upper surface of the substrate, an m-plane, an a-plane, an r-plane or the like may be used.Halbleitermehrschichtbereich 101As described above, the semiconductor multilayer region 101 may include, for example, the n-side semiconductor layer 110 including the n-side cladding layer 111 and the n-side optical guide layer 112; the active layer 120 located on the n-side semiconductor layer 110; and the p-side semiconductor layer 130 located on the active layer 120 and including the p-side optical guide layer 131, the p-side cladding layer 132, and the p-side contact layer 133.The semiconductor layer of the semiconductor multilayer region 101 is a III-V semiconductor layer. Examples of the group III-V semiconductor layer include a nitride semiconductor layer formed with a composition of InαAlβGa1-α-βN, (0≤α, 0≤β, α+β≤1).Examples of the element serving as the n-type impurity used for the nitride semiconductor layer include Si and Ge. Further, examples of an element serving as a p-type impurity include Mg. In this case, the nitride semiconductor layer may be formed of any conductivity type.n-side semiconductor layer 110The n-side semiconductor layer 110 includes one or more semiconductor layers each containing an n-type impurity. For example, the n-side semiconductor layer 110 may include the n-side cladding layer 111 having a refractive index n 111 and the n-side optical guide layer 112 having a refractive index n 112. The n-side semiconductor layer 110 may further include an undoped layer intentionally not doped with impurities.The refractive index n 111 and the refractive index n 112 are lower than the refractive index n 120 of the active layer 120. The refractive index n 111 and the refractive index n 112 are different from each other, and the refractive index n 111 is smaller than the refractive index n 112. for example.The n-side cladding layer 111 is disposed between the active layer 120 and the substrate 100. The n-side cladding layer 111 may be, for example, a nitride semiconductor layer. Examples of the nitride semiconductor include AlGaN and GaN. The film thickness of the n-side cladding layer 111 may be, for example, in a range of 0.45 μm to 3.0 μm. The content of the n-type impurity may be, for example, in a range of 1×10 17 cm -3 to 5×10 18 cm -3.The n-side optical guide layer 112 is disposed between the active layer 120 and the n-side cladding layer 111. The n-side optical guide layer 112 may be, for example, a nitride semiconductor layer. Examples of the nitride semiconductor include AlGaN, GaN, and InGaN. The film thickness of the n-side optical guide layer 112 may be, for example, in a range of 0.05 μm to 0.5 μm. The content of the n-type impurity may be, for example, in a range of 1×10 17 cm -3 to 5×10 18 cm -3.Active Layer 120The active layer 120 is disposed on the n-side optical guide layer 112. The active layer 120 emits light having a wavelength in a range of, for example, 360 nm to 800 nm. The active layer 120 may have a quantum well structure formed of one or more well layers and a plurality of barrier layers. The well layer and the barrier layer may be made of, for example, GaN, InGaN, AlGaN, or AllnGaN. The well layer is made of, for example, AlGaN, GaN or InGaN, which is a nitride semiconductor having a band gap energy lower than that of the barrier layer. The active layer 120 may have a multiple quantum well structure or a single quantum well structure. One or both of the well layer and the barrier layer may contain an impurity.p-side semiconductor layer 130The p-side semiconductor layer 130 includes one or more semiconductor layers each including a p-type impurity. The p-side semiconductor layer 130 is formed on the active layer 120. For example, the p-side semiconductor layer 130 may include the p-side optical guide layer 131 having a refractive index n 131 the p-side cladding layer 132 having a refractive index n 132 and the p-side contact layer 133 having a refractive index n 133 in this order from the substrate 100 side (in other words, from the active layer 120) side. The p-side semiconductor layer 130 may include a layer other than these layers. The p-side semiconductor layer 130 may include an undoped layer that is not intentionally doped with impurities.The refractive index n 131, the refractive index n 132 and the refractive index n 133 are lower than the refractive index n 120 of the active layer 120. The refractive index n 131, the refractive index n 132 and the refractive index n 133 may be different from each other. For example, the refractive index n 131 is higher than the refractive index n 132.The p-side optical guide layer 131 may be, for example, a nitride semiconductor layer. Examples of the nitride semiconductor include AlGaN and GaN. The film thickness of the p-side optical guide layer 131 may be, for example, in a range of 0.05 μm to 0.25 μm. The p-side optical guide layer 131 may be, for example, an undoped layer, and may contain a p-type impurity in a concentration in a range of 1×10 16 cm -3 to 1×10 18 cm -3.The p-side cladding layer 132 may be, for example, a nitride semiconductor layer. Examples of the nitride semiconductor include AlGaN and GaN. The p-side cladding layer 132 may have a single layer structure or a multilayer structure in which nitride semiconductor layers having different compositions are layered. The content of the p-type impurity may be in a range of, for example, 1×10 17 cm -3 to 1×10 20 cm -3. The p-side cladding layer 132 is not necessarily provided. In a case where the p-side cladding layer 132 is not provided, the amount of the p-type impurities in the semiconductor multilayer region 101 can be reduced, and the optical loss in the semiconductor multilayer region 101 can be reduced.The p-side semiconductor layer 133 may be, for example, a nitride semiconductor. Examples of the nitride semiconductor include AlGaN and GaN. The p-side contact layer 133 may have a single layer structure or a multilayer structure in which nitride semiconductor layers having different compositions are layered. The content of the p-type impurity may be in a range of 1×10 19 cm -3 to 1×10 22 cm -3.Waveguide StructureNext, the waveguide structure of the semiconductor laser element L 1 according to the first embodiment will be described in detail.In the following description, the waveguide structure of the second region 2 will be described first, and then the waveguide structure of the first region 1 will be described.The waveguide structure of the second region 2 includes the core region 21 having the refractive index n 21 and the cladding regions 22 having the refractive index n 22 located on two opposite sides of the core region 21, and is a waveguide for propagating light in a plurality of transverse modes (in other words, multi-transverse modes) in the longitudinal direction of the core region 21. In the present specification, the width of the core region 21 refers to a width in a direction orthogonal to the laminating direction of the semiconductor multilayered region 101 in a plane orthogonal to the optical axis of the waveguide. The thickness of the core region 21 refers to a thickness in the lamination direction of the semiconductor multilayer region 101 in a plane orthogonal to the optical axis of the waveguide. While the cladding regions 22 are provided on two opposite sides of the core region 21, the refractive indices of the two cladding regions 22 may be the same as or different from each other. When the refractive indices are different, the respective refractive indices n are 22A and n are 22B, and the maximum scattering angle θ max1 can be calculated using n 22A and n 22B.The number of transverse modes will be described below.In the following description, a symmetrical three-layered flat waveguide will be described for simplicity. A number N of transverse modes of light propagating through the core region 21 can be adjusted based on the following formula 1 by obtaining a standardized frequency V defined by the refractive index n 21 of the core region 21, the refractive index n 22 of the cladding regions 22, and the width of the core region 21. (N is an integer of 1 or more)In Formula 1, the standardized frequency V is expressed by V=k 0 n 21 a(2Δ) 1 / 2 k 0 is a wave number in vacuum, a is a half width of the core region 21, and Δ(=(n 212- n 222) / (2 n 212)) is a relative refractive index difference.For example, in Formula 1, N is the mode order of the transverse modes, and when the standardized frequency V is in a range of equal to or greater than π / 2 to less than 2n / 2 (i.e., π), light can propagate in two modes, a 0th-order mode (fundamental mode) and a first-order mode. When the normalized frequency V is equal to or greater than Nπ / 2 and less than (N+1)π / 2, the light can propagate in the 0th-order, first-order, second-order,..., and Nth-order modes, i.e., (N+1) modes.In this way, the number of transverse modes of light propagating through the second region 2 can be adjusted based on Formula 1. Specifically, it may be adjusted based on the width of the second ridge 135 b. For a semiconductor laser element having no ridge structure, it can be similarly adjusted based on the parameters constituting the waveguide.The number of transverse modes is preferably as large as possible to obtain high performance, and is, for example, 10 or more, preferably 30 or more, and more preferably 50 or more. Although the number of transverse modes is preferably as large as possible in order to obtain high performance, if it is excessively large, problems such as reduction in light concentration may occur. Thus, the number of transverse modes is, for example, 500 or less, preferably 300 or less, and more preferably 100 or less.As is apparent from the above description of formula 1, the number of transverse modes is determined by parameters including the width of the core region 21. Taking into account the number of transverse modes and the above-described heat dissipation, the width of the core region 21 is, for example, in a range of 15 μm to 120 μm, and more preferably, 45 μm to 100 μm.Diffraction grating 105As illustrated in FIG. 3, the diffraction grating 105 is provided in the first region 1. The diffraction grating 105 is preferably provided in the entire first region 1. In addition, the diffraction grating 105 is not provided in the second region 2. The Bragg wavelength in the diffraction grating is represented by the following formula 2. Formula 2 indicates that the effective diffraction grating period is the product of the equivalent refractive index and a pitch of the diffraction grating.The diffraction grating 105 may be formed by alternately (periodically) providing regions having different refractive indices in the light propagation direction. The diffraction grating 105 is located between two adjacent semiconductor layers, for example. The pitch of the diffraction grating 105 can be appropriately selected depending on the wavelength of light emitted from the active layer 120.The equivalent refractive index n 1 of the diffraction grating 105 is substantially the same for each transverse mode, and thus the Bragg wavelength λ B, which corresponds to each transverse mode, is also substantially the same. Thus, the half width of the oscillation wavelength of the laser light emitted from the semiconductor laser element L 1 is reduced. For example, the half width of the oscillation wavelength of the laser light emitted from the semiconductor laser element L 1 is in a range of 0.01 nm to 0.5 nm.In the first embodiment, the diffraction grating 105 is located between the n-side optical guide layer 112 and the n-side cladding layer 111, for example. Specifically, the diffraction grating 105 includes one or more first protrusion regions provided on the surface of the n-side cladding layer 111 and protruding toward the n-side optical guide layer 112, and one or more second protrusion regions provided on the surface of the n-side optical guide layer 112 and protruding toward the n-side cladding layer 111 alternately in the light propagating direction.The pitch (P) in Formula 2 is the sum of the length of a first protrusion region and the length of a second protrusion region in the light propagating direction.In the first embodiment, although the diffraction grating 105 is provided between the n-side optical guide layer 112 and the n-side cladding layer 111, it may be provided either in the n-side optical guide layer 112 or in the n-side cladding layer 111, or it may be provided between the n-side optical guide layer 112 and the active layer 120. The diffraction grating 105 may be provided on the p-side semiconductor layer 130 side.ElectrodesAs shown in FIGS. 3 and 4, the semiconductor laser element L 1 includes the p-electrode 150 and an n-electrode 160.In a case where the substrate 100 has conductivity, the n-electrode 160 may be disposed on the lower surface of the substrate 100. In a case where the substrate 100 has insulating properties, the n-electrode 160 may be formed on an exposed surface of the partially exposed n-side cladding layer 111.Examples of the material of the p-electrode 150 and the n-electrode 160 include a single layer film or a multilayer film of a metal such as Ni, Rh, Cr, Au, W, Pt, Ti, and Al, an alloy thereof, a conductive oxide containing at least one selected from Zn, In, and Sn.The p-electrode 150 may include a light-transmitting conductive film that is in contact with the burr 135 as a first electrode. By selecting a material such that the refractive index of the light-transmitting conductive film is smaller than the refractive index of the active layer 120 and the refractive index of the p-side semiconductor layer 130, the light-transmitting conductive film can be treated as a p-side cladding layer. The light-transmitting conductive film is, for example, ITO (indium tin oxide), IGZO (indium gallium zinc oxide), or the like. The insulating film 140 may be made of, for example, silicon oxide, aluminum oxide, or aluminum nitride.Calculation of Maximum Scattering Angle Θmax 1In the semiconductor laser element L 1 according to the first embodiment, the maximum scattering angle θ max1, to which reference is made when the position of the current shielding structure 10 is adjusted, can be determined using the factor M 2 given by the following formula 3 and being an index indicating the quantity of the laser light. The factor M 2 is an indicator indicating divergence from an ideal Gaussian beam, and the factor M 2 is 1 for an ideal Gaussian beam. That is, when the factor M 2 of the laser light emitted from the semiconductor laser element L 1 is found, it is possible to determine the degree of expansion of the laser light compared to an ideal Gaussian beam, and thus the maximum scattering angle θ max1 can be obtained. W 0 is the beam waist radius, and φ is the beam divergence angle.λ is the wavelength of laser light in a vacuum.The beam waist radius W 0 and the beam divergence angle φ can be measured using an optical system including a collimating lens 81 and a condenser lens 82 as illustrated in FIG. 5 in the following manner.A trajectory of laser light emitted from the first region 1, collimated by the collimating lens 81 and converged by the condenser lens 82, is tracked. Specifically, the beam diameter of the converged laser light is measured at various positions Bmp, the position where the beam diameter is smallest is estimated, and the beam diameter (beam waist radius W 0) at this position is determined. The divergence of the beam from the position where the beam diameter is the smallest is measured to determine the beam divergence angle φ. The definition of the parameters required for determining the factor M 2 is based on the international organization for standardization ISO 11146-1:2021 or ISO 11146-2:2021. The beam diameter is defined by, for example, D4σ (width of the second moment). The value of the current supplied to the semiconductor laser element L1 when the factor M 2 is measured is within a predetermined operating current range. The factor M 2 is determined, for example, using a commercially available measuring device (e.g., THORLABS BP209-VIS / M).The factor M 2 is calculated from Formula 3 using the beam waist radius W 0 and the beam divergence angle φ obtained as described above, and the maximum scattering angle θ max1 is determined based on the factor M 2 as described above. The trajectory of the laser light emitted from the second region 2 can be obtained from the factor M 2 and the trajectory of the laser light measured in the process of obtaining the factor M 2. Accordingly, imaginary lines v 1 expanding at the maximum diffusion angle θ max1 from two opposite ends of the emission end surface of the core region 21 are obtained. By comparing the positional relationship between the imaginary line and two opposite ends of the first region 1, the expansion of the laser light in the first region 1 can be examined.As illustrated in FIG. 5 and the like, the maximum scattering angle θ max1 is an angle formed by a straight line obtained by removing a curved portion from the imaginary line and a straight line that is an extension of the boundary between the core region 21 and the cladding region 22.Also, the factor M 2 of the laser light according to the first embodiment may be in a range of 2 to 100.When the beam diameter of the laser light at the laser light emitting end surface is smaller than the width of the first region 1 and the width of the first region 1 is substantially constant, it is apparent that two opposite end portions of the first region 1 are located outside the imaginary line v 1. Thus, the positional relationship between the width of the first region 1 and the imaginary line v 1 can be determined by first measuring the beam diameter of the laser light at the laser light emitting end surface.In the first embodiment, the semiconductor laser element L 1 according to the first embodiment has been described using a semiconductor laser element having a ridge structure as an example.However, the semiconductor laser element L 1 according to the first embodiment is not limited to a semiconductor laser element having a ridge structure, but may be a ridge waveguide semiconductor laser element or a hetero-structure waveguide embedded semiconductor laser element.The semiconductor material constituting the above-described semiconductor laser element may be a material other than a nitride semiconductor. The semiconductor material may be, for example, GaAs, InP, GaInP, GaInAsP, GaAlAs, or AllnGaP. In this case, it can be used as a semiconductor laser element having an oscillation wavelength in a range of 760 nm to 1060 nm. A semiconductor laser element made of a material other than these materials may also be used. A semiconductor laser element that emits ultraviolet light can be formed using, for example, aluminum nitride or boron nitride.The semiconductor laser element described so far can also be expressed as follows. The semiconductor laser element includes a semiconductor multilayer region 101 including an active layer 120 and a p-electrode 150 provided on the semiconductor multilayer region 101, and may include a waveguide structure. The semiconductor multilayer region 101 includes: (i) a first region 1 including a diffraction grating 105 that is a slab waveguide, and (ii) a second region 2 including a core region 21 and cladding regions 22 provided on two opposite sides of the core region 21.In a plan view, the first region 1 includes a central region 11 configured to cause light entering from the second region to propagate in the central region 11 and a peripheral region 12 located outside the central region 11. A current shielding structure 10 is provided at a position at least partially overlapping the peripheral region 12. Here, the first region 1 is a slab waveguide. In other words, in the first region 1, light is limited only in the laminating direction. Since the first region 1 where the diffraction grating 105 is provided is a slab waveguide, the equivalent refractive index is almost the same even for different transverse modes, and the selected wavelengths (Bragg wavelengths) in the diffraction grating 105 are tuned. There may be an optical confinement region in the peripheral region 12. Even in this case, the central region 11 of the first region 1 is a slab waveguide.Second EmbodimentA semiconductor laser element L 2 according to the second embodiment is the same as the semiconductor laser element L 1 according to the first embodiment in that it includes the current shielding structure 10 formed of a region of the insulating film 140, but it differs therefrom in the structure of the p-electrode 150.Specifically, in the first region 1 of the semiconductor laser element L 2 according to the second embodiment, the first electrode 151 is not disposed to be in contact with the entire upper surface of the p-side contact layer 133 on the ridge 135 of the semiconductor multilayer region 101. Instead, as illustrated in FIG. 6, the first electrode 151 is disposed inside the first opening portion 140 asuch that the width of the first electrode 151 is limited to the width of the first opening portion 140 a, and the first electrode 151 is in contact with the p-side contact layer 133.In the semiconductor laser element L 2 according to the second embodiment configured as described above, the current in the peripheral region 12 can be shielded, and the reactive current in the peripheral region 12 can be reduced to reduce heat generation.Thus, according to the semiconductor laser element L 2 of the second embodiment, laser light can oscillate and propagate in multiple transverse modes, and thus it is possible to provide the semiconductor laser element L 1 that can achieve high power conversion efficiency.In the semiconductor laser element L 2 according to the second embodiment, the first electrode 151 is disposed within the first opening portion 140 asuch that the width of the first electrode 151 is limited to the width of the first opening portion 140 a, and the first electrode 151 is in contact with the p-side contact layer 133. This structure can prevent the current in the first electrode 151 from expanding in the lateral direction, and the current can be shielded more effectively.In the semiconductor laser element L 2 according to the second embodiment, the p-electrode 150 in the second region 2 may have any suitable structure, and may have a structure the same as in the first embodiment, or the first electrode 151 may be disposed within the second opening portion 140 bas in the first region 1.The semiconductor laser element L 2 according to the second embodiment has the same configuration as the semiconductor laser element L 1 according to the first embodiment except for the p-electrode 150. For example, the semiconductor laser element L2 is a multi-transverse mode semiconductor laser element.Third EmbodimentA semiconductor laser element L 3 according to the third embodiment is different from the semiconductor laser element L 1 according to the first embodiment in the configuration of the current shielding structure.Specifically, as illustrated in FIG. 7, a current shielding structure 13 in the semiconductor laser element L 3 according to the third embodiment is composed of an oxide film 133 aprovided on a surface of the semiconductor multilayer region 101 (a surface of the p-side contact layer 133) and including an opening region 13 aon the central region 11, and is configured such that current is introduced from the p-electrode 150 into the central region 11 via the opening region 13 a.In the semiconductor laser element L 3 according to the third embodiment, for example, in the first region 1, the first electrode 151 may be disposed in contact with the entirety of an upper surface of the p-side contact layer 133 on the ridge 135 of the semiconductor multilayer region 101.In the semiconductor laser element L 3 according to the third embodiment, the oxide film 133 athat constitutes the current shielding structure 13 can be formed by oxidizing a surface of the p-side contact layer 133, for example. In this way, the first electrode 151 and the p-side contact layer 133 may be Schottky-connected via the oxide film 133 a, and the current shield structure 13 may be formed.In the semiconductor laser element L 3 according to the third embodiment configured as described above, the current in the peripheral region 12 can be shielded, and the reactive current in the peripheral region 12 can be reduced to reduce heat generation.Thus, according to the semiconductor laser element L 3 of the third embodiment, laser light can oscillate and propagate in multiple transverse modes, and thus it is possible to provide the semiconductor laser element L 3 that can achieve high power conversion efficiency.In the semiconductor laser element L 3 according to the third embodiment, the second region 2 may have any suitable current introduction structure, and may have a current introduction structure the same as or different from that of the first embodiment.For example, in the second region 2, a second oxide film that is disposed in the semiconductor multilayer region 101 and includes the second opening portion 140 bthat is narrower than the opening portion 13 amay be disposed on the waveguide to allow a current to be introduced into the second region 2 via the second opening portion 140 b. In this way, in the second region 2, the core region 21 and the cladding regions 22 can be provided on two opposite sides thereof, and light in a multi-transverse mode corresponding to the width of the second opening portion 140 bcan be oscillated.In the semiconductor laser element L 3 according to the third embodiment, the configuration of the semiconductor multilayer region 101 and the like is the same as that in the semiconductor laser element L 1 according to the first embodiment, unlike the current shielding structure 13. For example, the semiconductor laser element L3 is a multi-transverse mode semiconductor laser element.Fourth EmbodimentA semiconductor laser element L 4 according to the fourth embodiment is different from the semiconductor laser element L 1 according to the first embodiment in the configuration of the current shielding structure.Specifically, as illustrated in FIG. 8, a current shielding structure 14 in the semiconductor laser element L 4 according to the fourth embodiment is composed of a block layer 132 aprovided in the p-side semiconductor layer 130 of the semiconductor multilayer region 101 and including an opening portion 14 ain the central region 11 to limit the current introduced from the p-electrode 150 via the opening portion 14 a.In the semiconductor laser element L 4 according to the fourth embodiment, for example, in the first region 1, the first electrode 151 may be disposed so as to be in contact with the entire upper surface of the p-side contact layer 133 on the ridge 135 of the semiconductor multilayer region 101. The block layer 132 amay be provided by forming an undoped layer in a part of the p-side semiconductor layer 130.While FIG. 8 illustrates an example in which the block layer 132 ais provided by making a part of the p-side cladding layer 132 undoped, it is sufficient that the block layer 132 ais provided above the active layer 120, in other words, on the p-electrode 150 side. For example, the block layer 132 amay be provided in the p-side optical guide layer 131 or in the p-side contact layer 133. In another example, in the p-side semiconductor layer 130, in addition to the p-side optical guide layer 131, the p-side cladding layer 132, and the p-side contact layer 133, an undoped layer may be provided as the additional layer, and the undoped layer may serve as the block layer 132 a.The semiconductor laser element L 4 according to the fourth embodiment configured as described above can shield the current in the peripheral region 12 and reduce the reactive current in the peripheral region 12 to reduce heat generation.Thus, according to the semiconductor laser element L 4 of the fourth embodiment, laser light can oscillate and propagate in multiple transverse modes, and thus it is possible to provide the semiconductor laser element L 4 that can achieve high power conversion efficiency. In the semiconductor laser element L 4 according to the fourth embodiment, the second region 2 may have any suitable current introduction structure, and may have a current introduction structure the same as or different from that of the first embodiment.For example, in the second region 2, a second block layer provided in the semiconductor multilayer region 101 and including the second opening region 140 bwhich is narrower than the opening region 14 amay be disposed on the waveguide, and a current may be introduced into the second region 2 via the second opening region 140 b. In this way, in the second region 2, the core region 21 and the cladding regions 22 can be provided on two opposite sides thereof, and light in a multi-transverse mode corresponding to the width of the second opening portion 140 bcan be oscillated.In the semiconductor laser element L 4 according to the fourth embodiment, the configuration of the semiconductor multilayer region 101 and the like except for the current shielding structure 14 is the same as in the semiconductor laser element L 1 according to the first embodiment. For example, the semiconductor laser element L4 is a multi-transverse mode semiconductor laser element.Modified ExampleIn the above description of the embodiments, for example, in the example of the semiconductor laser element L 1 according to the above-described first embodiment, the width of the first opening portion 140 aprovided in the insulating film 140 constituting the current shielding structure 10 is constant.However, considering that the laser light emitted from the second region 2 propagates through the first region 1 at the maximum scattering angle θ max1 the width of the first opening portion 140 amay not be constant, and the width of the opening portion may increase toward the emission end surface of the first region 1, as illustrated in the first opening portion 140 cin FIG. 9. With such a configuration, it is possible to efficiently introduce a current into an opening portion and to efficiently reduce the region in which a reactive current flows. For example, it is preferable that the width of the opening portion extends along imaginary lines extending at the maximum diffusion angle θ max1.The same applies to the second to fourth embodiments, and the width of the opening portion may increase toward the emission end surface of the first region 1 for the opening portion 13 aformed in the oxide film 133 aof the third embodiment and the opening portion 14 aformed in the block layer 132 aof the fourth embodiment.Examples 1 to 3 and Comparative Example 1The semiconductor laser element L2 was prepared and the output of the laser light was measured. In order to prepare the semiconductor laser element L2, the n-side cladding layer 111, the n-side optical guide layer 112, the active layer 120, the p-side optical guide layer 131, the p-side cladding layer 132 and the p-side contact layer 133 were laminated on a GaN substrate. The first ridge 135 aand the second ridge 135 bhave been obtained by removing a portion of the p-side cladding layer 132 up to a part of the p-side optical guide layer 131. The width of the first ridge 135a was 345 μm, and the width of the second ridge 135b was 90 μm. The diffraction grating 105 was provided in the n-side semiconductor layer 110 in the first region 1, and the period of the diffraction grating 105 was 96 nm. The width of the diffraction grating 105 was 350 μm. The first electrode 151 and the insulating film 140 were laminated over the p-side contact layer 133 in this order. At this time, the second opening portions 140 bhave been formed to have all the width of 84 μm, and the first opening portions 140 aand the first opening portion 140 cof the insulating film 140 have been formed to have different shapes. Accordingly, four samples of Examples 1 to 3 and Comparative Example 1 were obtained. The width of the first opening portions 140 aand the first opening portion 140 cin each example is as shown in Table 1. In Example 3, the width of the first opening portion 140 cis gradually increased from 90 μm to 101 μm. That is, in Comparative Example 1, the width of the first opening portion 140 ais substantially equal to the width of the diffraction grating 105, in Examples 1 and 2, the width of the first opening portion 140 ais narrower than that of the sample of Comparative Example 1, and in Example 3, the first opening portion 140 ais provided to have a shape widening along imaginary lines widening at the maximum scattering angle θ max1.A current was introduced into the semiconductor laser elements prepared according to Examples 1 to 3 and Comparative Example 1 to obtain the data shown in Table 1. Table 1 Table 1Example 13048,61,5830,6Example 21019,61,7633,9Example 390-1019,81,8034,4Comparative Example 13428,31,5129,1As is apparent from these results, the obtained semiconductor laser element in Examples 1 to 3 had higher power conversion efficiency than Comparative Example 1.9,5 A current was applied to the sample (4), the half width for the wavelength of the emitted light was measured, and as a result, it was 0.15 nm. Although the semiconductor laser element L2 is a multi-transverse mode semiconductor laser, a small wavelength variation has been obtained.Although the embodiment and the modified examples of the present disclosure have been described above, various modifications are possible as long as the configuration based on the technical idea of the present disclosure is included. Moreover, various changes may be made to the combination and order of the components in the embodiment and the modified examples within the scope and spirit of the present disclosure.In addition to the above embodiments, the following aspects are disclosed, for example.Aspect 1A semiconductor laser element comprising: a semiconductor multilayer region comprising an active layer, the semiconductor multilayer region comprising: (i) a first region comprising a diffraction grating, and (ii) a second region configured to cause laser light to propagate in multiple transverse modes in the second region, the second region comprising: a core region, and cladding regions located on two opposite sides of the core region; at least one electrode disposed on the semiconductor multilayer region; and a current shielding structure; wherein the semiconductor laser element has a waveguide structure; and in a plan view, the first region comprises: a central region where light entering from the second region propagates, and a peripheral region located outside the central region; and in a plan view, the current shield structure is located at a position at least partially overlapping the peripheral region.Aspect 2A semiconductor laser element comprising: a semiconductor multilayer region comprising an active layer, the semiconductor multilayer region comprising: (i) a first region comprising a diffraction grating, the first region being a slab waveguide, and (ii) a second region comprising: a core region, and cladding regions located on two opposite sides of the core region; at least one electrode disposed on the semiconductor multilayer region; and a current shielding structure; wherein the semiconductor laser element has a waveguide structure; and in a plan view, the first region comprises: a central region where light entering from the second region propagates, and a peripheral region located outside the central region; and in a plan view, the current shield structure is located at a position at least partially overlapping the peripheral region.Aspect 3The semiconductor laser element according to Aspect 1 or 2, wherein: the core region has a refractive index n 21 ; the cladding regions have a refractive index n 22 ; the central region has a refractive index n 1 ; laser light emitted from the second region propagates through the first region at a maximum scattering angle θ max1 determined by the refractive index n 1, the refractive index n 21 and the refractive index n 22 ; The central region includes a region located within imaginary lines expanding from two opposite ends of an emission end surface of the core region at the maximum scattering angle θ max1.Aspect 4The semiconductor laser element according to any one of Aspects 1 to 3, wherein: the current shielding structure includes an insulating film located on the semiconductor multilayer region and including an opening portion on the central region; and at least a part of the electrode is located in the opening portion.Aspect 5The semiconductor laser element according to Aspect 4, wherein: the at least one electrode includes a first electrode disposed in the opening portion; and the first electrode contacts the semiconductor multilayered portion on an inner side of the opening portion.Aspect 6The semiconductor laser element according to Aspect 4, wherein: the at least one electrode comprises: a first electrode disposed on and in contact with the semiconductor multilayer region, and a second electrode disposed on the first electrode; and the second electrode is connected to the first electrode via the opening region.Aspect 7The semiconductor laser element according to any one of Aspects 4 to 6, wherein a width of the opening portion increases toward an emission end surface of the first region.Aspect 8The semiconductor laser element according to any one of Aspects 4 to 7, wherein: the second region includes a second insulating film disposed on the semiconductor multilayer region and including a second opening region narrower than the opening region on the second region; and the electrode is configured to allow a current to be introduced into the second region via the second opening region.Aspect 9The semiconductor laser element according to any one of Aspects 1 to 3, wherein: the current shielding structure includes an oxide film provided on a surface of the semiconductor multilayer region and including an opening portion on the central region; and the electrode is configured to allow a current to be introduced into the central region via the opening portion.Aspect 10The semiconductor laser element according to Aspect 9, wherein the opening area increases in a width toward an emission end surface of the first region.Aspect 11The semiconductor laser element according to Aspect 9, wherein a width of the opening portion is constant.Aspect 12The semiconductor laser element according to any one of Aspects 9 to 11, wherein: the second region includes a second oxide film disposed in the semiconductor multilayer region and includes, on the second region, a second opening region narrower than the opening region; and the electrode is configured to allow a current to be introduced into the second region via the second opening region.Aspect 13The semiconductor laser element according to any one of Aspects 1 to 3, wherein: the current shielding structure includes a block layer provided in the semiconductor multilayer region and including an opening portion on the central region, and the electrode is configured to allow a current to be introduced into the central region via the opening portion.Aspect 14The semiconductor laser element according to Aspect 13, wherein a width of the opening portion increases toward an emission end surface of the first region.Aspect 15The semiconductor laser element according to Aspect 13, wherein a width of the opening portion is constant.Aspect 16The semiconductor laser element according to any one of aspects 13 to 15, wherein: the second region includes a second block layer located in the semiconductor multilayer region and including, on the second region, a second opening region narrower than the opening region; and the electrode is configured to allow a current to be introduced into the second region via the second opening region.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2023-175306

[0001] JP 2024-159383

[0001] JP 2011-151238

[0003]

Claims

A semiconductor laser element comprising: a semiconductor multilayer region comprising an active layer, the semiconductor multilayer region comprising: (i) a first region comprising a diffraction grating, and (ii) a second region configured to cause laser light to propagate in multiple transverse modes in the second region, the second region comprising: a core region, and cladding regions located on two opposite sides of the core region; at least one electrode disposed on the semiconductor multilayer region; and a current shielding structure; wherein the semiconductor laser element has a waveguide structure; and in a plan view, the first region comprises: a central region where light entering from the second region propagates, and a peripheral region located outside the central region; and in a plan view, the current shield structure is located at a position at least partially overlapping the peripheral region.A semiconductor laser element comprising: a semiconductor multilayer region comprising an active layer, the semiconductor multilayer region comprising: (i) a first region comprising a diffraction grating, the first region being a slab waveguide, and (ii) a second region comprising: a core region, and cladding regions located on two opposite sides of the core region; at least one electrode disposed on the semiconductor multilayer region; and a current shielding structure; wherein the semiconductor laser element has a waveguide structure; and in a plan view, the first region comprises: a central region where light entering from the second region propagates, and a peripheral region located outside the central region; and in a plan view, the current shield structure is located at a position at least partially overlapping the peripheral region.The semiconductor laser element according to claim 1 or 2, wherein: the core region has a refractive index n 21 ; the cladding regions have a refractive index n 22 ; the central region has a refractive index n 1 ; laser light emitted from the second region propagates through the first region at a maximum scattering angle θ max1 determined by the refractive index n 1, the refractive index n 21 and the refractive index n 22 ; The central region includes a region located within imaginary lines expanding from two opposite ends of an emission end surface of the core region at the maximum scattering angle θ max1.The semiconductor laser element according to any one of claims 1 to 3, wherein: the current shielding structure comprises an insulating film located on the semiconductor multilayer region and comprising an opening portion on the central region; and at least a part of the electrode is located in the opening portion.The semiconductor laser element according to claim 4, wherein: the at least one electrode comprises a first electrode disposed in the opening portion; and the first electrode contacts the semiconductor multilayered portion on an inner side of the opening portion.The semiconductor laser element according to claim 4, wherein: the at least one electrode comprises: a first electrode disposed on and in contact with the semiconductor multilayer region, and a second electrode disposed on the first electrode; and the second electrode is connected to the first electrode via the opening region.The semiconductor laser element according to any one of claims 4 to 6, wherein a width of the opening portion increases toward an emission end surface of the first region.The semiconductor laser element according to any one of claims 4 to 7, wherein: the second region comprises a second insulating film disposed on the semiconductor multilayer region and comprising a second opening region narrower than the opening region on the second region; and the electrode is configured to allow a current to be introduced into the second region via the second opening region.The semiconductor laser element according to any one of claims 1 to 3, wherein: the current shielding structure comprises an oxide film provided on a surface of the semiconductor multilayer region and comprising an opening portion on the central region; and the electrode is configured to allow a current to be introduced into the central region via the opening portion.The semiconductor laser element according to claim 9, wherein the opening area increases in a width toward an emission end surface of the first region.The semiconductor laser element according to claim 9, wherein a width of the opening portion is constant.The semiconductor laser element according to any one of claims 9 to 11, wherein: the second region includes a second oxide film disposed in the semiconductor multilayer region and including, on the second region, a second opening region narrower than the opening region; and the electrode is configured to allow a current to be introduced into the second region via the second opening region.The semiconductor laser element according to any one of claims 1 to 3, wherein: the current shielding structure comprises a block layer provided in the semiconductor multilayer region and comprising an opening portion on the central region, and the electrode is configured to allow a current to be introduced into the central region via the opening portion.The semiconductor laser element according to claim 13, wherein a width of the opening portion increases toward an emission end surface of the first region.The semiconductor laser element according to claim 13, wherein a width of the opening portion is constant.The semiconductor laser element according to any one of claims 13 to 15, wherein: the second region includes a second block layer located in the semiconductor multilayer region and including, on the second region, a second opening region narrower than the opening region; and the electrode is configured to allow a current to be introduced into the second region via the second opening region.

Images