Patent ID: 7289546

Claim:
A semiconductor laser comprising: a first cladding layer of a first conductivity type and having a band gap energy Eg(C 1 ); a first guide layer having a band gap energy Eg(G 1 ), on said first cladding layer; an active layer having a band gap energy Eg(A), for generating a laser beam, and on said first guide layer; a second guide layer having a band gap energy Eg(G 2 ), on said active layer; and a second cladding layer of a second conductivity type, having a band gap energy Eg(C 2 ), and on said second guide layer, wherein at least one of said first guide layer and said second guide layer has a thickness of at least 100 nm, and the larger one of the difference of Eg(G 1 ) from Eg(A) and the difference of Eg(G 2 ) from Eg(A) is no more than 0.66 times the smaller of the difference of Eg(C 1 ) from Eg(A) and the difference of Eg(C 2 ) from Eg(A).