Phasing of two amplifier channels for the coherent combining of laser beams with a total power of 60 W

We have demonstrated stable operation of a system for maintaining a constant phase difference between two laser channels with a total output power of 60 W. The system is based on a twochannel fibre amplifier with phase modulators based on piezoceramic spools. At a main piezo element modulation frequency of 11 kHz, the phasing time after thermal and mechanical influences on the active medium is 100 ms.