Tunable picosecond SESAM mode-locking ytterbium-doped double-clad LMA PCF oscillator

Abstract A picosecond tunable ytterbium-doped double-clad fiber oscillator with semiconductor saturable absorber mirror (SESAM) mode-locking large mode area (LMA) photonic crystal fiber (PCF) is demonstrated. Without any tunable elements in the oscillator, we obtain self-starting mode locking ytterbium-doped fiber oscillator tunable over 35.5 nm. The center wavelength in the ranges from 1028.5 nm to 1064 nm with excellent beam quality is achieved by proper adjusting the polarization beam splitter (PBS), half-wave plate (HWF) and SESAM in the laser cavity. The output power ranges from 0.76 W to 1.01 W at the different center wavelengths under the same incident pump power. A narrow spectral bandwidth with only 0.25–0.5 nm and pulsed duration with 7.9 ps have been obtained at the different center wavelengths. The repetition rate has been measured to be about 45.9 MHz, which has a slight change for the different center wavelengths.