Semiconductor laser producing visible light

A semiconductor laser producing visible light comprising:

• a first conductivity type GaAs substrate;
• a first conductivity type (Al.sub.w Ga.sub.1-w).sub.0.5 In.sub.0.5 P cladding layer disposed on said substrate;
• a (Al.sub.z Ga.sub.1-z).sub.0.5 In.sub.0.5 P active layer disposed on said first conductivity type cladding layer wherein 0.ltoreq.z.ltoreq.w;
• a second conductivity type (Al.sub.w Ga.sub.1-w).sub.0.5 In.sub.0.5 P cladding layer having a lattice constant and disposed on said active layer;
• a first conductivity type In.sub.1-x Ga.sub.x As.sub.1-y P.sub.y current blocking layer disposed on part of said second conductivity type cladding layer wherein y is approximately equal to -2x+2, 0.5.ltoreq.x<1, and 0<y.ltoreq.1 so that the lattice constant of said current blocking layer is substantially the same as the lattice constant of said second conductivity type cladding layer;
• a current concentration and collection structure in contact with said second conductivity type cladding layer for concentrating current flow in a central part of said active layer;
• facets transverse to said cladding layers and said active layer forming an optical resonator therewith for supporting laser oscillation;
• and
• first and second electrodes disposed in contact with said substrate and current concentration and collection structure, respectively.