We present a detailed experimental study on the influence of dispersion on the pulse
formation in passively modelocked vertical-external-cavity surface-emitting lasers
(VECSELs). We have demonstrated that the shortest pulse duration requires slightly positive
dispersion to balance the nonlinear phase shift induced by strong semiconductor gain and
absorber saturation. This is in contrast to soliton modelocking in ion-doped solid-state lasers–
but similarities remain and will be discussed. Our results are in good qualitative agreement …

During the less than ten years since the first demonstration of modelocked vertical external
cavity surface emitting lasers (VECSELs), their performance strongly improved and starts to
become comparable to standard modelocked lasers based on ion-doped glasses or
crystals. Moreover, the semiconductor gain material has important advantages such as cost-
efficient mass-production, emission wavelength and bandwidth control by bandgap
engineering. Picosecond pulses with average output powers> 2 W were achieved and the …