Coherent fiber-optics-array collimator based on a single unitary collimating lens: proposal design and experimental verification

In this paper, we propose a design of coherent fiber-optics-array collimator (CFAC) that is mainly composed of a single unitary collimating lens and a prism. The CFAC system is presented conceptually, and corresponding parameters are theoretically analyzed using a geometrical optics method. Then, we set up a proof-of-concept experiment to verify the validity of the CFAC system with three coherent fiber lasers distributed along the symmetry axis through the center of the single unitary lens. After that, we realize the synchronous aberrationless collimating of the three beams with only one collimating lens system and their parallel propagation by utilizing a specific prism array. Finally, we successfully achieve a coherent beam combination of the laterally distributed three beams using a single-frequency dithering algorithm. Through an active piston phase control, the residual phase errors among the laser beams are suppressed below λ/26. By comparing the experimental results with the simulation results, we can see that the distribution of the closed-loop far-field intensity pattern detected by the charge-coupled infrared camera basically matches the ideal intensity distribution.