High average power coherent femtosecond pulse combining system based on an all fiber active control method

Abstract

We experimentally demonstrate a high average power coherent polarization beam combining system of two-channel femtosecond fiber chirped-pulse amplifiers based on our all fiber active control method comprising an active phase locking loop and adaptive control loop of optical path drift for the first time. A coherent combining efficiency of 87% is achieved at the combined power of 4.3 W, which drops with the average power scaling. The combined average power finally reaches 313 W with a coherent combining efficiency of 79% and the corresponding compressed pulse duration is 827 fs. The reasons for the loss in combining efficiency are experimentally investigated. Further power scaling is restricted by the deterioration of the laser mode, but it is still possible if the performance of the single femtosecond fiber chirped-pulse amplifier is improved.