| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor laser having a structure that can be fabricated with high yield, while exhibiting low return light noise characteristics derived utilizing self excitation, and being low in astigmatism. SOLUTION: In a semiconductor laser, a first conductivity-type clad layer 20, an activated layer 4, and second conductivity-type clad layers 31 and 32 are formed on a first conductivity type semiconductor substrate 1, and a saturable absorbing layer is inserted into at least one of the first or the second conductive clad layer(s), the saturable absorbing layer having a band gap smaller than and the same conductivity as that of the layer(s), into which it is inserted. In such a semiconductor laser, valence band energy noncontinuous relaxation layers 36 and 37 are provided next to at least one of the upper or lower layer of the saturable absorbing layer. By 'valence band energy noncontinuous relaxation layer' is meant a layer that has noncontinuous valence band energy with an intermediate value between the saturable absorbing layer and the clad layer next thereto.
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