SELF-OSCILLATION SEMICONDUCTOR LASER DEVICE

PROBLEM TO BE SOLVED: To provide a semiconductor laser device which has a low element resistance, a low thermal resistance, a low passage resistance, and a small operating current; and is capable of self oscillation. SOLUTION: The self-oscillation semiconductor laser device comprises at least a first-conductivity-type clad layer, an active layer, a second conductivity-type first clad layer, a second-conductivity-type second clad layer having a stripe-like ridge structure, a current block layer so formed on the second-conductivity-type first clad layer as to sandwich the both ridge side surfaces, and a second-conductivity-type third clad layer formed on the ridge of the second-conductivity-type second clad layer and the current block layer in the vicinity of the ridge, all formed on the substrate and the cross section of the ridge perpendicular to the longitudinal direction of the stripe of the ridge structure is a trapezoid satisfying the following relation; 0.05