Semiconductor laser device

Claim 1

In a semiconductor laser device comprising an active layer for laser oscillation and optical guiding layers for guiding laser light sandwiching said active layer therebetween, at least one of said optical guiding layers being formed by a superlattice, the optical refractive index of which is lower than that of the active layer and is gradually decreased in the direction from the portion of said optical guiding layer adjacent to the active layer to the outside of said optical guiding layer, said superlatticed optical guiding layer being composed of alternate layers consisting of a plurality of Al x Ga 1-x As layers, the thickness of each of which is L B , and a plurality of Al y Ga 1-y As layers (1≧x>y≧0), the thickness of each of which is L z , the layer thicknesses L B and L Z , respectively, are equal to or less than the mean free-path of the carrier, and said optical refractive index of the superlatticed optical guiding layer being determined depending upon the average AlAs mole fraction x eff in the Al x Ga 1-x As and Al.sub. y Ga 1-y As mixed crystals of each of the alternate layers constituting the superlatticed optical guiding layer that is represented by the formula: x eff =(L B 'x+L Z 'y)/(L B +L Z ), whereby said gradual decrease in the optical refractive index of the superlatticed optical guiding layer is achieved by gradual changes in the layer thicknesses L B and L Z .