New time-domain model for active mode locking, based on the transmission line laser model

A new time-domain model for active mode-locking in semiconductor lasers, coupled to external cavities including a filter, is developed. Unlike previous time domain models, the propagating field is considered, rather than the photon density. This allows time-domain filters to be used to model the spectral dependencies of gain, spontaneous emission and dispersive components. Also, Fourier transforms of the field reveal the output spectrum. The new model is compared with results from a previous time-domain model before the effects of bandwidth limiting on pulse shape are investigated. Results show that transform limited pulses can be generated. However, their stability is critically dependent on the drive conditions and the spontaneous emission coupled to the lasing mode