Fast antiresonant quantum-dot SESAMs for MIXSEL integration

In this work, we demonstrate for the first time that an antiresonant SESAM can modelock a VECSEL with the same spot size on gain and saturable absorber. This has been made possible thanks to a systematic study on the influence of QD-SESAMs growth parameters and post-growth annealing on the macroscopic optical SESAM properties. The modulation depth (DeltaR) of the annealed single layer antiresonant QD-SESAMs is on the order of 0.5%, which is too low for VECSEL modelocking. We therefore increased the number of absorber layers and have experimentally demonstrated that for multiple-layer QD-SESAMs the modulation depth can be tuned with the ML coverage (i.e. QD density) and is proportional to the number of QD layers, while the saturation fluence (Fsat) stays constant. An antiresonant MIXSEL design has low dispersion and would enable high growth tolerance which is important for the manufacturing requirements of large scale applications.