Abstract

In target-in-the-loop experiments, it is essential to take into account speckle and realistic turbulences for a better understanding. Here we present a numerical simulator of our recently demonstrated coherent beam combining of fiber amplifiers through atmospheric turbulence on a remote surface using the backscattered signal [1]. In the setup recalled on fig. 1, coherent combining (based on frequency-tagging techniques) of 3 fiber amplifiers is achieved with a single detector in the plane of the laser emitter. Artificial turbulences are generated over a distance of 1m. The feedback loop keeps adjusting the relative phase difference between the three emitted beams so that to keep the error signal equal to zero and therefore having the light seen by the detector maximized. It has been observed that when adding a ~1mm diameter hole before the detector lens (thus limiting the detector aperture), beam combining was also achieved on the remote surface, even though the propagation to and from the scattering surface is turbulent. Thus, the addition of an aperture limiting hole enables the beam combining on a remote surface even after turbulent propagation.

© 2009 IEEE