Zhi Dong, Ma Yanxing, Tao Rumao, Zhou Pu, Wang Xiaolin, Chen Zilun, Si Lei
College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, 410073, China.
Sci Rep. 2019 Feb 26;9(1):2783. doi: 10.1038/s41598-019-39304-0.
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.
光纤激光阵列的相干光束合成（CBC）是一种很有前景的方法，可克服单光纤激光器的功率扩展限制，并实现具有良好光束质量的高亮度激光，可用于相干共形投影系统（CCPS）进行光束投影以及用于具有巨大潜力的自由空间激光通信系统。迄今为止，所有通过几公里大气湍流演示的CBC系统都采用了准直光束，由于波前重叠效率低下，这显著降低了最终的CBC效果。另一方面，聚焦CCPS比准直投影系统有很多优点，因为投影光束的波前更接近会聚球面波的波前。在本文中，我们首次基于自适应光纤准直器阵列设计并制造了聚焦CCPS，这是通过自适应光纤准直器引入可控球差来实现的。搭建了一个CBC系统来评估和验证其性能。结果表明，与准直CCPS相比，中心瓣的能量部分可增加44%，这与理论分析结果吻合良好。
