Disclosed is an optoelectronic device on a semi-insulator substrate, of the type comprising, stacked on one another, at least:one substrate made of semi-insulator material,one lower confinement layer with a first type of conductivity,at least one active layer in strip form, andan upper confinement layer with a second type of conductivity. In this device, the lower confinement layer covers one side of the semi-insulator substrate in passing beneath the active layer and coming to a stop substantially vertically to this active layer and the upper confinement layer covers the other side of the semi-insulator substrate in passing over the active layer and coming to a stop substantially vertically to this active layer. The disclosure can be applied notably to the fabrication of lasers.