Active coherent beam combination of two high-power single-frequency nanosecond fiber amplifiers

We report on active coherent beam combining of two single-frequency nanosecond fiber amplifiers by using stochastic parallel gradient descent algorithm. Each fiber amplifier produces an average power of more than 100W by using three-stage cascaded amplification. The two laser beams are actively phase-locked with a total average power of 215.8W, producing similar to 8 ns pulses at 10 MHz repetition rate. The contrast of the far-field intensity pattern of the coherently combined beam is more than 83%. (C) 2012 Optical Society of America