Fourier-Limited 19-ps Yb-Fiber Seeder Stabilized by Spectral Filtering and Tunable Between 1015 and 1085 nm

We report a passively mode-locked picosecond ytterbium-doped fiber laser operating in the normal dispersion regime, tunable over 70 nm around 1.05
$\mu{\rm m}$
. Mode-locking operation is achieved through a free-space coupled semiconductor saturable absorber. An external grating in Littrow configuration is used for both tuning and mode-locked stabilization through spectral filtering. Pulse duration of 19 ps with pulse repetition rates below 20 MHz is obtained with a maximum average output power of 1.5 mW.