Abstract: A distributed-feed back semiconductor laser diode comprises a substrate of n-type conductivity GaAs having a pair of opposed surfaces, a pair of sides and a pair of ends. In sequence on one of the opposed surfaces are a first clad layer of n-type conductivity graded AlGaAs; a first confining layer of undoped AlGaAs; a first quantum well layer of undoped GaAs; a barrier layer of undoped AlGaAs; a second quantum well layer of undoped GaAs; a second confining layer of undoped AlGaAs; a spacer layer of p-type conductivity graded AlGaAs; a plurality of spaced, parallel grating bars of p-type conductivity AlGaAs extending across the spacer layer parallel to the ends of the substrate; a second clad layer of p-type conductivity graded AlGaAs over and between the grating bars; and contact layer of p+ type conductivity GaAs. A first conductive contact layer contacts the contact layer and a second conductive contact layer is on the other opposed surface of the substrate.