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Effect of group-velocity dispersion on the stability of quantum-cascade lasers

Abstract. As the effect of group-velocity dispersion (GVD) on the stability of midinfrared quantum-cascade lasers (QCLs) has not been explored so far, both amplitude and phase instabilities of QCLs were analyzed in the presence of a background saturable absorber in the lasing medium. The investigation was carried out through the linearization of the Maxwell–Bloch formalism for the lasing medium by including second-order dispersion of group velocity and intensity-dependent loss accounting for the saturable absorber. The effect of the GVD on laser instability was found to be strongly related to the strength of the saturable absorber and pumping. The effect of the GVD is more significant at lower pumping levels and with weaker saturable absorbers.