THEORETICAL AND EXPERIMENTAL-STUDY OF INHOMOGENEOUSLY PUMPED DISTRIBUTED-FEEDBACK LASERS

We have investigated inhomogeneously pumped index-coupled distributed feedback (DFB) laser structures both theoretically and experimentally. Using a transfer matrix method, an optimized device structure was des igned which drastically suppresses the longitudinal sidemodes by conce ntrating the injection current in the region close to the phase-shift position. In this way, a high yield of monomode lasers together with a n easy fabrication technique was achieved without the necessity of end facet antireflection coating. Experimental evidence of the improvemen t of the single-mode stability is given first by three-section DFB las ers operated by two different injection currents. Second, the proposed three-segment laser pumped with a single drive current was implemente d simply by splitting up the contact of a mushroom type 2 X lambda/8 p hase-shifted DFB laser. We observed the theoretically predicted enhanc ed stability of the Bragg mode with a sidemode suppression ratio of 52 dB and a higher yield of monomode lasers compared with uniformly pump ed conventional DFB laser devices.