Analytical propagation of traveling-waves in mode-locked vertical-external-cavity surface-emitting lasers

Passive mode-locking in vertical-external-cavity surface-emitting lasers (VECSELs) is studied based on an analytical approach for the propagation of traveling waves in two coupled vertical cavities. We obtain stable pulses of few tens of picoseconds at 15 GHz repetition rate in agreement with recent experimental findings. Design rules to extend the regime of stable mode-locking are discussed.