RELAXATION OSCILLATION FREQUENCY OF DFB LASERS WITH GAIN COUPLING

Using the spatially-dependent rate equations based on the Green's function analysis, we investigate the dependency of the relaxation oscillation frequency on the complex coupling coefficient and other parameters of gain-coupled DFB lasers by simultaneously considering spatial-hole-burning, gain saturation and gain compression, An explicit expression for the relaxation oscillation frequency for DFB lasers including the longitudinal spatial effects has been obtained, It is found that antiphase gain-coupling significantly enhances the local effective differential gain in the gain-coupled DFB laser and hence increases the relaxation oscillation frequency, We have also shown for the first time that the modal linewidth enhancement factor alpha(M) plays an important role in determining the relaxation oscillation frequency of gain-coupled DFB lasers, especially when the built-in index coupling is weak.