Patent ID: 7852897

Claim:
A distributed feedback semiconductor laser in which the lasing wavelength can be changed, comprising: a semiconductor substrate; a semiconductor layer portion provided on the semiconductor substrate and including a first active layer having a first bandgap energy, a second active layer having a second bandgap energy, and an intermediate layer having a third bandgap energy, the intermediate layer optically coupling the first active layer and the second active layer, the first active layer, the intermediate layer, and the second active layer being arranged in that order in a predetermined axis direction; a diffraction grating having a period, the diffraction grating being optically coupled with the first active layer and the second active layer of the semiconductor layer portion; a first electrode for injecting carriers into the first active layer; a second electrode for injecting carriers into the second active layer; and a third electrode for supplying the intermediate layer with a signal for wavelength tuning, wherein the diffraction grating extends in the predetermined axis direction, the period of the diffraction grating is uniform in the predetermined axis direction, and the third bandgap energy of the intermediate layer is larger than the first bandgap energy of the first active layer and the second bandgap energy of the second active layer.