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The combination of high output power and femtosecond pulses from VECSELs and MIXSELs would be very attractive for many applications. To explore the limitations, a quantitative understanding of the pulse formation processes is required. Our numerical simulations showed a good qualitative agreement with experimental results in the picosecond regime. By minimizing intracavity group delay dispersion (GDD) and improving gain bandwidth and SESAM parameters, our model predicts pulses as short as 250 fs. As a first step we minimized GDD with a top coating which provides values between ±10 fs 2 over a range of 30 nm around the design wavelength. Keywords: modelocking, VECSEL, SESAM, femtosecond 1. INTRODUCTION Passively modelocked Vertical External Cavity Surface Emitting Lasers (VECSELs [1]) or Modelocked Integrated eXternal-cavity Surface-Emitting Lasers (MIXSELs [2]) using semiconductor satu rable absorbers have achieved multi-Watt average output power in the picosecond regime. Recently, up to 6.4 W of average power in 28-ps pulses were achieved from a MIXSEL [3]. Femtosecond pulse generation, however, has been power limited well below 1 W. To date the average output power of femtosecond VECSELs based on quantum well (QW) gain structures has been limited to |
