Coherent beam combining of fiber amplifier arrays and application to laser beam propagation through turbulent atmosphere

Abstract

Coherent beam combining of fiber amplifier arrays is a promising way to increase power of fiber lasers, and overcome the physical limitations to fiber laser power scaling. We performed the coherent combining of fiber amplifier arrays using active control of the phase of each amplifier. The phase fluctuations in the fiber amplifiers have been measured and their effect on the beam combining process stability evaluated. We extended the coherent beam combining technique to perform wavefront shaping, in order to deliver a high brightness beam after turbulent atmospheric propagation. We present experimental results exhibiting the capability of the modulation multiplexing technique that we implemented to compensate phase fluctuations due to turbulent atmospheric propagation on the laser beam path. Moreover, and for the first time to our knowledge, we demonstrate automatic coherent combining of fiber amplifiers on a diffuse surface, after propagation through turbulent atmosphere, without any external turbulence measurement subsystem.