Distributed feedback semiconductor laser

Abstract

In a semiconductor laser with a diffraction grating which carries out optical feedback, the diffraction grating has, at the center of the laser cavity, a phase-shift structure 5 of a half period of the basic grating period which is averaged over the whole grating. And in the central region of this grating, a section of period variation (a second grating 4 and a third grating 6) with different grating periods from the basic period is incorporated in such a manner as the amounts of variation from the basic period spread, from the center towards both facets of the laser cavity, with the equal absolute value but the reversed sign to each other. According to the semiconductor laser of the present invention, the longitudinal intensity distribution of electric field in the laser cavity is uniform. Therefore the laser does not show the variation in the ratio of the forward to the backward lasing output power even when the bias current is altered, and is easy to monitor the lasing output on the system.

Dependencies are inferred from the claim text.