High-power Yb-fiber comb with feed-forward control of nonlinear- polarization-rotation mode-locking and large-mode-area fiber amplification

We report on a simple scheme to precisely control carrier-envelope phase of a nonlinear-polarization-rotation modelocked self-started Yb-fiber laser system with an average output power of ̃7 Wand a pulse width of 130 fs. The offset frequency was locked to the repetition rate of ̃64.5 MHz with a relative linewidth of ̃1.4 MHz by using a selfreferenced feed-forward scheme based on an acousto-optic frequency shifter. The phase noise and timing jitter were calculated to be 370 mrad and 120 as, respectively.