Laser modelocking beyond Haus: the coherent master equation

Germán_J. De_Valcárcel
Universitat de València, Departament d'Òptica, Dr. Moliner 50, 46100 Burjassot, Spain
Haus master equation (HME) is the standard theoretical approach to laser modelocking which has proven successful in many different situations. However HME is unable to account for light-matter coherent effects which are at the basis of certain types of laser modelocking and frequency comb generation in, e.g., quantum-dot and quantum-cascade lasers. Here we present a new theoretical framework for master equation laser modelocking modeling, which consistently incorporates coherent effects: the coherent master equation (CME). As a proof of its coherent nature, CME captures the Risken-Nummedal-Graham-Haken self-modelocking instability. We apply the new approach to an amplitude-modulated modelocked laser, whose CME yields predictions that differ from HME which are most prominent when the gain recovery time is comparable or shorter than the cavity roundtrip time. These divergent predictions include the existence of non-Gaussian pulses and the asymmetric effect of the modulation frequency, which are verified experimentally in an actively modelocked semiconductor laser with a long external cavity.