PURPOSE: To arbitrarily change the strength of distributed feedback by external signals by a method wherein a reverse conductivity type semiconductor region connected to control terminals which has period becoming the primary, secondary, or tertiary diffraction grating for oscillation frequency is provided in the neighborhood of a laser active layer.

CONSTITUTION: A P type Ga0.7Al0.3As clad layer 2, an undoped GaAs layer 3, an N type Ga0.7Al0.3As layer 4, a P type GaAs cap layer 6, and an Au-Ge-Ni electrode 7 are provided on a P type GaAs substrate. Tungsten buried electrodes 5 are provided in the layer 4, and an N type stripe region 11 is provided in the layers 4 and 6. A bonding electrode 14 is provided on the buried electrode, and an N-side bonding electrode is provided on the electrode 7. The voltage given to control terminals can be varied and variable distributed feedback can be given to laser oscillation by a method wherein the reverse conductivity type semiconductor region or the buried electrodes which are connected to control terminals are provided in contact with the laser active layer or in the neighborhood thereof in this manner.