Highly efficient coherent conformal projection system based on adaptive fiber optics collimator array

Coherent beam combination (CBC) of fiber laser array, which is a promising approach to overcome the power scaling limitations of the single fiber laser and to achieve high-brightness laser with good beam quality, can be employed in coherent conformal projection system (CCPS) for beam projection and free space laser communication system with enormous potential. To date, all the demonstrated CBC system through several kilometers atmospheric turbulence have employed collimated beams, which significantly decrease the final CBC effect because of the inefficient wavefront overlap. On the other hand, focused CCPS has lots of advantages over collimated projection system since the wave front of the projected beam is closer to that of a convergent spherical wave. In this paper, we design and manufacture focused CCPS based on an adaptive fiber optics collimator array for the first time, which is achieved by introducing controllable spherical aberration through the adaptive fiber optics collimator. A CBC system is setup to evaluate and validate its performance. Results show that compared with the collimated CCPS, the energy portion of the central lobe could be increased by a factor of 44%, which agrees well with the theoretical analysis.