PURPOSE: To realize a distribution feedback semiconductor laser characterized only in TE mode oscillation by a method wherein an optical waveguide constituted of a layer with its forbidden band width larger than that of an activation layer is coupled to a distribution feedback waveguide and its surface is coated with a metal layer with the intermediary of an insulating layer.

CONSTITUTION: To an activation waveguide 10 including an activation layer having an uneven periodic structure 100, an optical waveguide 50 is coupled, with its forbidden band width larger than that of said activation layer. The waveguide 10 is provided with a clad layer 30 thereon. On the waveguide 50, through the intermediary of an insulating film 200, a metal layer 300 of Au or the like is provided. The end face of the activation region is so structured as to suppress the Fabry-Perot mode. Oscillation is generated by an oscillating frequency that is determined by the diffraction lattice organized by the periodic structure of the activation waveguide 10. Said light is coupled with the optical waveguide layer 50, to be reflected by its end face and return to the activation waveguide 10. Due to the metal layer 300, loss is greater in the TM mode than in the TE mode. Accordingly, a distribution feedback semiconductor laser oscillating only in the TE mode is obtained.