Relative carrier-envelope phase Stabilization of hybridly synchronized ultrafast Yb and Er fiber-laser systems with the feed-forward scheme

Stabilization of the relative carrier-envelope (CE) phase for hybridly synchronized two-color fs Yb and Er fiber-laser systems is demonstrated for the first time by utilizing the feed-forward scheme based on an acousto-optic frequency shifter. The slow drift issues arising from the feed-forward scheme are solved by adding the in-loop relative CE frequency coarse stabilization via modulating the laser pump current. Sub-fs timing locking between the two-color pulses is still maintained due to the fast response and large locking range of hybrid synchronization. The approach provides an alternative way to obtain phase-stable synchronized two-color pulses with higher pulse energies.