A diffraction grating is provided in the vicinity of a GRIN-SCH-MQW active layer
formed between a radiation side reflection coating provided on a radiation end
face of a laser beam and a reflection coating provided on a reflection end face
of the laser beam, and on the radiation side reflection coating side. An n-InP
layer which covers the upper part of the diffraction grating is also provided,
so that the current from the p-side electrode is prevented from being injected
to the vicinity of the diffraction grating by the n-InP layer. An n-InPGaAsP diffusion
prevention layer forms a non-current injection area so as to suppress alloying
with the p-side electrode.
