A semiconductor laser diode type of a buried-hetero structure (BH-LD) is disclosed. The LD provides a mesa, a first burying layer, and a second burying layer, where the burying layers are provided in respective sides of the mesa so as to expose a top of the mesa. The mesa includes a lower cladding layer, an active layer, and an upper cladding layer, where the cladding layers have conduction type opposite to each other and, combined with the burying layers, constitute a carrier confinement structure. The second burying layer has an even surface overlapping with an even surface of the first burying layer, and has a thickness in a portion of the even surface that is thinner than a thickness thereof in a portion except for the even surface.

A method for fabricating a semiconductor device on a semiconductor substrate and an optical laser system utilizing laser devices fabricated from the method. The optical laser system includes a first laser device configured to generate laser light, an optical assembly configured to receive the generated laser light from the first laser device, and collimate the received laser light from the first laser device to provide collimated laser light. The optical laser system further comprises a second laser device configured to receive the collimated laser light, and amplify the received collimated laser light via application of a drive current to generate amplified laser light, wherein at least one of the first laser device and the second laser device is fabricated via the method for fabricating a semiconductor device on a semiconductor substrate.

A semiconductor laser includes: a multi-quantum well layer in a mesa structure; a buried layer comprising a semi-insulating semiconductor, the buried layer being in contact with each of both sides of the mesa structure; a first cladding layer with a first conductivity type, the first cladding layer having a lower refractive index than the multi-quantum well layer; a high refractive index layer configured to not absorb light oscillating in the multi-quantum well layer, the high refractive index layer having a higher refractive index than the first cladding layer; a diffraction grating layer at least partially constituting a diffraction grating capable of diffracting the light oscillating in the multi-quantum well layer, the diffraction grating layer not contacting the high refractive index layer; a substrate with the first conductivity type; and a second cladding layer with a second conductivity type above the multi-quantum well layer.