Semiconductor laser device, semiconductor laser module, and welding laser light source system

A semiconductor laser device that lases in a multiple transverse mode, comprising:

• a substrate having a main surface;
• and
• a stacked structure including a first conductivity-side semiconductor layer, an active layer, and a second conductivity-side semiconductor layer that are sequentially stacked above the main surface of the substrate,
• wherein the second conductivity-side semiconductor layer includes an opening that delimits a current injection region,
• a pair of side faces is formed in portions of the stacked structure that range from part of the first conductivity-side semiconductor layer to the second conductivity-side semiconductor layer,
• the active layer has a second width greater than a first width of the opening,
• the pair of side faces in at least part of the first conductivity-side semiconductor layer is inclined to the main surface of the substrate,
• a maximum intensity position in a light distribution of light guided in the stacked structure, in a direction of a normal to the main surface of the substrate, is within the first conductivity-side semiconductor layer,
• each of the pair of side faces includes a first side face on a side close to the substrate and a second side face on a side farther away from the substrate,
• θ1 is less than 90 degrees, θ1 being an angle formed by a direction of a normal to the first side face and the direction of the normal to the main surface of the substrate,
• θ2 is greater than 90 degrees, θ2 being an angle formed by a direction of a normal to the second side face and the direction of the normal to the main surface of the substrate,
• the pair of side faces is covered with a dielectric film, and
• the first side face and the second side face are an interface between the dielectric film and the stacked structure.