Novel concepts in modelocked VECSELs

The goal of this thesis was to exploit the flexibility of vertical external-cavity surface-emitting lasers (VECSELs) modelocked with a semiconductor saturable absorber mirror (SESAM). By using conventional and novel concepts, the parameter range and performance of such ultrafast VECSELs was successfully expanded with respect to the repetition rate, absorber technology, electrically pumped lasers and self-referenceable frequency combs. A previous limitation for VECSELs was the low pulse repetition rate regime. Within this thesis, a 100 MHz VECSEL based on a standard cavity and a 250 MHz multi-pass arrangement were demonstrated, which represents two convenient solutions to operate VECSELs in this regime. Besides the SESAM, the novel absorber material graphene caught the attraction of the ultrafast VECSEL community. A graphene saturable absorber mirror (GSAM) was fabricated and used for VECSEL modelocking. Furthermore, the GSAM devices were compared to state-of-the-art SESAMs. Motivated by the demand of reducing the complexity of ultrafast pulse sources, an improved electrically pumped VECSEL was developed. With an optimized gain chip and a resonant, low-saturation fluence SESAM, a record performance with a modelocked electrically pumped VECSEL was achieved, including the highest average (53.2 mW) and peak power (4.7 W), the shortest pulses (2.5 ps) and the highest repetition rate (18.2 GHz). With respect to new frontiers in optically pumped modelocked VECSELs, the carrier-envelope-offset frequency of an ultrafast VECSEL was detected by employing a 231 fs seed oscillator and a subsequent amplification and compression scheme. The results obtained within the scope of this thesis demonstrate the flexibility of the vertical emitting semiconductor disk laser technology and show the high potential for future applications.