Distributed feedback semiconductor laser for outputting beam of single wavelength

摘要

First and second diffraction grating layers are provided above a semiconductor substrate, and are spaced from each other in an output direction of a beam with a flat connecting layer sandwiched therebetween. An active layer is disposed above or below the first and second diffraction grating layers and the connecting layer. A cladding layer is disposed above the active layer or above the first and second diffraction grating layers and the connecting layer. A diffraction grating including the first and second diffraction grating layers has a plurality of slits penetrating from an upper surface to a lower surface that are perpendicular to the output direction of the beam. The connecting layer is formed from two layers grown epitaxially in a direction perpendicular to the output direction of the beam. One of the two layers is formed of the same material as the first and second diffraction grating layers.