Accurate simulation of laser diode noise with arbitrary levels of optical feedback

Optical feedback provided by a grating reflector or an external mirror can be used to select a distinct longitudinal mode, to achieve considerable linewidth narrowing or to tune the emission frequency of a laser. When the optical feedback is strong, the multiple reflections in the external cavity have to be taken into account, and the laser dynamics must be described by a set of nonlinear rate equations. In this work, the numerical method used is generalized to obtain, by simulation from a set of nonlinear rate equations, accurate estimates of intensity and frequency noise for arbitrary levels of feedback. From those rate equations, expressions for the RIN and FN spectra taking into account all Langevin noise sources are obtained analytically through the usual small-signal analysis.