External cavity semiconductor laser model for the strong feedback regime

Abstract

We present a formalism describing the dynamics of a semiconductor diode and apply it to the study of the dynamics of external cavity lasers within the strong regime. The formalism is based upon the usual travelling wave phenomenological model for the field and carriers within the semiconductor gain medium. Since the non-radiative recombination time of the carriers is typically much longer than the diode round trip time, we use a multiple scales analysis to obtain a model much simpler in form than the travelling wave model, but as accurate, without assuming that the gain within the diode is uniform. We apply this model to the external cavity laser. Rather than including multiple external cavity reflections explicitly, we include all external cavity reflections through the introduction of a single additional feedback parameter and one extra term in the field equation. In the limit of a single external cavity reflection, our field equation reduces to a form of the well-known Lang–Kobayashi equation that describes very weak external feedback. For strong feedback, we examine both the steady state and dynamical laser properties such as small signal response and large signal current modulation.