Semiconductor laser device and method for producing the same

A method for producing a semiconductor laser device, comprising the steps of:

• forming a grating layer on a semiconductor substrate, the grating layer having a first region and a second region;
• forming a diffraction grating having periodic projections and recesses in the first region of the grating layer;
• forming an active layer on the grating layer and a cladding layer on the active layer;
• forming a first mask on the cladding layer;
• forming a semiconductor ridge structure portion extending in a first direction by etching the cladding layer with the first mask;
• forming a second mask on the semiconductor ridge structure portion;
• and
• forming a pair of first trenches along both side faces of the semiconductor ridge structure portion by etching the active layer and the grating layer with the second mask until the pair of first trenches penetrates through the grating layer, the pair of first trenches defining both side faces of the active layer and the grating layer, wherein
• in the step of forming the semiconductor ridge structure portion, the semiconductor ridge structure portion is formed by forming a pair of second trenches, the pair of second trenches defining both side faces of the semiconductor ridge structure portion,
• the side faces of the active layer and the grating layer are separated from the side faces of the semiconductor ridge structure portion in a second direction intersecting with the first direction, and
• in the step of forming the pair of first trenches, the pair of first trenches is formed in the first region of the grating layer.