Patent ID: 7839911

Claim:
A semiconductor laser device having a ridge stripe structure, comprising: a clad layer having a protrusion that extends from a front cleavage plane to a rear cleavage plane, and that is included in the ridge stripe structure; and a current block layer covering the clad layer, except an upper surface of the protrusion, wherein: a width W of the upper surface of the protrusion is nonuniform between the front cleavage plane and the rear cleavage plane, when (i) Wf denotes a width of the upper surface at the front cleavage plane, (ii) Wr denotes a width of the upper surface at the rear cleavage plane, (iii) L denotes a distance between the front cleavage plane and the rear cleavage plane, and (iv) Sc denotes an area of the upper surface, in a distance range where a distance from the front cleavage plane is shorter than or equal to L/2, Wf>Wr, L/8×(3Wf+Wr)<Sc≦0.12×Wf, and ½ (Wf+Wr)<W≦Wf in an arbitrary position within the distance range, a taper angle formed in a distance range, that starts from an arbitrary position X in a range where a distance D from the front cleavage plane is in a range of 0.45≦L≦0.55L, and that ends in a position of the rear cleavage plane, is larger than a taper angle formed in a distance range that starts from a position of the front cleavage plane and ends in the position X, and when α denotes the taper angle formed in the distance range from the position X to the position of the rear cleavage plane, and β denotes the taper angle formed in the distance range from the position of the front cleavage plane to the position X, α is in a range of 0.27°≦α≦0.37°, and β is in a range of 0.01°≦β≦0.1°.