Semiconductor laser

A vertical structure semiconductor laser comprising:

• an n-type doped semiconductor bottom cladding layer,
• a light guide superposed on the bottom cladding layer and including a central region including a semiconductor active layer, and
• a p-type doped semiconductor top cladding layer superposed on said light guide, which laser is characterized in that said light guide further comprises:
• a semiconductor bottom guide layer having the following two adjacent bottom parts:
• an undoped first bottom part adjacent the central region, and
• an n-type doped second bottom part adjacent the bottom cladding layer,
• a semiconductor top guide layer having the following two adjacent top parts:
• an undoped first top part adjacent the central region, and
• a p-type doped second top part adjacent the top cladding layer,
• in that the first bottom and top parts form a non-doped region more than 0.5 μm thick, and in that the refractive index difference between one or each cladding layer and the adjacent guide layer is less than 0.02.