DISTRIBUTED FEEDBACK SEMICONDUCTOR LASER

PROBLEM TO BE SOLVED: To provide a λ/4 phase shift DFB laser, which is easy to be manufactured to obtain an optical output equivalent to a uniform grating DFB laser. SOLUTION: A distributed feedback semiconductor laser comprises a diffraction grating having a coupling coefficient changing in a resonator axis direction by a combination of a plurality of gratings, including differentiated periods or phase differences in the distributed feedback semiconductor laser, having a λ/4 phase shifting point on the diffraction grating. In this laser, heights of ridges of the plurality of the gratings are constant. The periods or the phase differences of the gratings are changed at respective predetermined regions in the resonator axis direction, and the coupling coefficient of the grating is changed stepwisely in the resonator axis direction. COPYRIGHT: (C)2004,JPO