| 摘要 |
PURPOSE:To maintain a single lateral mode even if high output power is implemented, by providing double light guides, in which another light guide mechanism is provided in one light guide, thereby broadening the width of an active layer, which is determined by the width of a mesa part, and enlarging the cross sectional area of the light guides. CONSTITUTION:A mesa part 100 is provided on a semiconductor substrate 1. In the structure of the mesa part 100, a first semiconductor layer 30 of P type Al0.3Ga0.7As, whose forbidden band width is larger than an active layer 4, is held by a second semiconductor layer 20 of N type GaAs, whose forbidden band width is smaller or equal to the active layer 4. The active layer 4 is positioned so that the upper part and the lower part of the mesa 100 are separat ed. Therefore, the active layer 4 at the side of the upper part of the mesa is surrounded by a clad layer 5 of N type Al0.3Ga0.7As, whose refractive index is smaller than that of the active layer. Thus one light guide is formed. Light is guided in the light guide having a width W1. Even if the width W1 is made broad, a single lateral mode is maintained owing to the presence of an inner light guide having a width W2.
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