Recent progress in semiconductor gain-coupled DFB laser research

Summary form only given. Eight years have passed since the first demonstration of semiconductor gain-coupled (GC) distributed-feedback (DFB) lasers. During this period, a number of advantages of the GC and CC (complex-coupled) DFB lasers over the conventional index-coupled (IC) ones have been set forth. Those advantages sound, however, somewhat optimistic when people come across a serious question whether they should manufacture them. In this presentation, we first summarize what has been achieved so far by different research institutes. Then, we will try to make an objective comparison with the conventional DFB laser from present point of view, so that people may know which advantage is practicable and which is not at this moment. In addition, we review recent research activities on the GC DFB laser and related devices that should lead to ultimate light sources in the twenty first century.