Experimental study on coherent beam combination of fiber amplifiers using adaptive power-in-the-bucket cost function

Beam combination (BC) of fiber amplifiers based on master-oscillator-power-amplifier configuration is an outstanding way to generate high power and high beam quality laser output, where the tip/tilt aberrations among beamlets are considered as a serious influence factor to BC effects. In this paper, a new tip/tilt control method based on adaptive power-in-the-bucket (PIB) cost function is proposed to solve the problem of restricted tip/tilt correcting value in current BC systems. Experimental setup of coherent BC of two-channel 2 W fiber amplifier array is established. Home-made piezoelectric-ring fiber-optic phase-modulator and adaptive fiber-optics collimator are employed to correct piston- and tip/tilt-type aberrations, respectively. The feasibility of proposed tip/tilt control method using adaptive-PIB is demonstrated and nice effect of coherent BC is achieved.