www.lphys.orgLASER PHYSICS LETTERS EDITORIAL BOARD

Abstract: A passively mode-locked ytterbium-doped large-mode-area photonic crystal fiber oscillator operating in the vicin-ity of zero cavity dispersion is demonstrated. The self-starting mode-locking operation is achieved by a high contrast saturable absorber mirror. Two mode-locking regimes with opposite signs of net cavity dispersion are investigated. At a net cavity disper-sion of –0.0035 ps2, the fiber laser directly generates 10-nJ laser pulses with an average power of 630 mW at 65.3 MHz repetition rate. The pulses can be dechirped to 78 fs by extracavity disper-sion compensation. The pulse energy is scaled up to 18 nJ, yield-ing an average power of 1.2 W, when the cavity dispersion is set at 0.0035 ps2. In this regime, the laser output can be extracavity-dechirped to 120 fs. Dynamics of pulse evolution in the fiber laser is illustrated by numerical simulation, which agrees well with ex-perimental results. PC F