Enhanced maximum intrinsic modulation bandwidth of complex-coupled DFB semiconductor lasers

DFB lasers with complex (gain and index) coupling are shown to have reduced K-factors, that is increased maximum intrinsic modulation bandwidths, compared with pure gain-coupled lasers. The K-factor is shown to be dependent on the ratio and phase of the index coupling to the gain coupling. Appropriate choice of the ratio of index coupling to gain coupling can triple the maximum intrinsic modulation bandwidth of the laser.