Influence of instantaneous mode competition on the dynamics of semiconductor lasers

Comprehensive theoretical investigations of the influence of instantaneous mode-competition phenomena on the dynamics of semiconductor lasers are introduced. The analyzes are based on numerical simulations of the multimode rate equations superposed by Langevin noise sources that account for the intrinsic fluctuations associated with the spontaneous emission. Numerical generation of the Langevin noise sources is performed in such a way as to keep the correlation of the modal photon number with the injected electron number. The gain saturation effects, which cause competition phenomena among lasing modes, are introduced based on a self-consistent model. The effect of the noise sources on the mode-competition phenomena is illustrated. The mode-competition phenomena induce instantaneous coupling among fluctuations in the intensity of modes, which induce instabilities in the mode dynamics and affect the state of operation. The dynamics of modes and the characteristics of the output spectrum are investigated over wide ranges of the injection current and the linewidth enhancement factor in both AlGaAs-GaAs and InGaAsP-InP laser systems. Operation is classified into stable single mode, stable multimode, hopping multimode, and jittering single mode. Based on the present results, the experimental observations of multimode oscillation in InGaAsP-InP lasers are explained as results of the large value of the linewidth enhancement factor.