Phasing of several gain channels for coherent and spectral combining of laser beams

A system for maintaining a constant phase difference between several laser channels is designed and an algorithm of its operation under a slow (with a characteristic time of no less than 100 ms) variation in the radiation phase in a channel is developed. Different possible regimes of operation of the measurement system and versions for phase difference maintaining are analysed and an optimal algorithm is elaborated. Long-term stable operation of the system under thermal and mechanical effects on the active medium is experimentally demonstrated by the example of a seven-channel fibre amplifier with a working wavelength of 1.064 μm.