Semiconductor laser device having plural active regions

A monolithically integrated semiconductor laser device capable of providing a plurality of light beams, each light beam being different in wave length, said laser device comprising:

• a semiconductor substrate of a first conductivity type
• a plurality of multi-layer double heterostructures, formed sequentially on said semiconductor substrate, and having a separating semiconductor layer of a second conductivity type formed between said respective multi-layer double hetero-structures, each of said multi-layer double hetero-structures including successively, at least a first cladding semiconductor layer of the first conductivity type, an active semiconductor layer of the first conductivity type, and a second cladding semiconductor layer of the first conductivity type, said active semiconductor layer having a relatively narrower bandgap than those of said first and second cladding semiconductor layers;
• a diffusion region diffused with the impurity of the second conductivity type to convert the conductivity type of said diffusion region to said second conductivity type;
• said diffusion region reaching said first cladding semiconductor layer of said multi-layer double hetero-structure, adjacent to said semiconductor substrate, and through said plurality of multi-layer double hetero-structures and at least one of said separating semiconductor layers, thereby forming transversely a plurality of p-n junctions in said active semiconductor layers, each of said p-n junctions causing an active region adjacent to said p-n junction to emit stimulated radiation when said p-n junctions are forward biased and pumped with current above a threshold current level;
• means for separately forward biasing each of said p-n junctions and for applying current thereto;
• and means for providing feedback of said stimulated radiation to said active region.