PURPOSE: To suppress absorption of laser beam at a light emitting end surface to prevent temperature rise by irradiating an area near the light emitting end surface of a semiconductor laser having a beam activating layer with an energy beam.

CONSTITUTION: When irradiated with an energy beam, aluminum composition value at a part of beam activating layer 3a increases up to 0.3 from about 0.1. In general, increase of this aluminum composition value works for enlarging an optical forbidden band width of AlxGa1-xAs, because Zn included in a P-type clad layer 5 near a GRIN-SCH layer 3 is diffused into the beam activating layer 3a when it is irradiated with an energy beam. Therefore, even after the irradiation of light beam, carrier concentration in the beam activating layer 3a in the area near the light emitting end surface does not become excessive, free carrier loss at the light emitting end surface can be lowered and expansion of an optical forbidden band width of the beam activating layer 3a can be generated only in the part irradiated with an energy beam.