Design of high-power surface-emitting DFB lasers for suppression of filamentation

The susceptiblity of curved-grating, surface-emitting, distributed-feedback lasers to filamentation and multi-mode instability was studied by numerical modeling and analysis. It was found that reflections from the ends, edges and output window can intiate instability, leading to filmantation. These effects can be suppressed by using absorbers between the end of the stripe and teh cleaved ends of the chip, wide unpumped-grating edges, and introducing wedge into the substrate to alleviate the effect of window reflections. It was also found that increasing the optical-confinement factor improves stability. A specific design is presented that is stable up to values of antiguiding that is larger than that measured in InGaAs quantum well lasers.