Injection laser with an inverted waveguiding rib

Claim 1

An injection laser element epitaxially grown on a substrate and having two opposite substantially parallel end faces, comprising, as considered in the growth direction: a lower passive layer of one conductivity type, a planar active layer of the other conductivity type, an upper passive layer sandwiching said active layer between itself and said lower passive layer, and being of a material with a lower refractive index and higher band gap than, and of the same conductivity type as, the material of said active layer, a blocking layer covering said upper passive layer except for a region of a stripe extending from one to the other of the opposite end faces substantially normal thereto, and an intermediate index layer of a material with a refractive index intermediate those of the materials of said active and upper passive layers and of a conductivity type identical to that of the material of said upper passive layer and opposite to that of the material of said blocking layer, said intermediate index layer covering said blocking layer and extending into said stripe region into contiguous relationship with the material of said upper passive layer, the refractive indexes of the materials of said intermediate index, blocking, upper passive, and active layers being such in relation to one another and to the thicknesses of the respective layers that said intermediate layer is so optically coupled at the laser emission wavelength with said active layer as to provide a guided wavelength in the direction of propagation that is shorter in the region of said active layer that is overlaid by said stripe than in the adjacent regions of said active layer.