NONLINEARITIES IN HIGH-INDEX-COUPLED LAMBDA 4-SHIFTED DISTRIBUTED-FEEDBACK SEMICONDUCTOR-LASERS/

Distributed-feedback lambda/4-shifted laser diodes with index coupling factor kappa as high as 300 cm-1 have been tested. The linewidths hav e been compared with the results of two computer models of the device including nonlinear effects. The fundamental role of local intensity-d ependent effects, which take place inside the cavity, is pointed out. It explains the absence of any saturation of the curve of the linewidt h against inverse power that is usually expected in this kind of devic e at high injection levels.