Influence of nonlinear gain on intrinsic bandwidth of quantum well and strained layer semiconductor lasers

Optimisation of the bandwidth of semiconductor lasers subject to direct intensity modulation has been undertaken taking account of the effect of nonlinear gain suppression on the damping of relaxation oscillations. A novel relationship between the damping and the 3 dB intrinsic bandwidth of semiconductor lasers has been obtained and is used to examine the effect of the damping in limiting the intrinsic bandwidth of conventional and advanced (quantum well and strained layer) semiconductor lasers. It is shown that enhanced nonlinear gain in quantum well and strained layer lasers significantly limits bandwidth improvements anticipated for such advanced laser structures on the basis of their relatively high differential gain. The operating conditions appropriate to maximum intrinsic bandwidth have been identified in these cases