Semiconductor laser

Abstract

The invention has such a double hetero structure () that an active layer () is sandwiched by an n-type clad layer () and a p-type clad layer () on a semiconductor substrate () made of GaAs. In the p-type clad layer (), for example, an n-type current constriction layer () consisting of at least two layers is provided in such a configuration that a first layer () thereof closer to the active layer is made of a material having almost the same refractive index as the p-type clad layer and a second layer () thereof farther from the active layer is made of a material having a smaller refractive index than the first layer (). By this configuration, a self-excitement type and high-power semiconductor laser can be obtained which operates in a stable manner up to a high power without generating a kink while being self-excited at a low power. Another embodiment of the invention comprises a current constriction layer having an n-type in which a stripe trench is formed in the p-type clad layer, and a light confinement layer having a smaller refractive index than the p-type clad layer is formed at the current constriction layer facing the active layer, so as to be of a p-type or non-doped type. By this configuration, a semiconductor laser can be obtained which operates up to a high power without generating a kink.