PURPOSE: To prevent the end face of a resonator from being broken even in case a light density is high and to contrive the speedup of a distributed feedback laser by a method wherein a light density in the central part of the resonator is made relatively higher than that in the vicinity of the end face of the resonator.

CONSTITUTION: A buffer layer 2, a clad layer 3, an active layer 4, a barrier layer 5 and a guide layer 6 are continuously grown in order on a substrate 1. Then, a secondary diffraction grating 11 is formed in the layer 6 by an interference exposure and a chemical etching. At this time, the depth of etching is adjusted so that the product of a resonator length and a coupling coefficient is a prescribed value. Thereby, a light density in the central part of a resonator becomes relatively higher than that in the vicinity of the end face of the resonator, a breaking of the end face is never generated, the upper limit of a modulated frequency is not restricted and a distributed feedback laser can be speeded up.