Ramirez Lourdes Patricia, Hanna Marc, Bouwmans Géraud, El Hamzaoui Hicham, Bouazaoui Mohamed, Labat Damien, Delplace Karen, Pouysegur Julien, Guichard Florent, Rigaud Philippe, Kermène Vincent, Desfarges-Berthelemot Agnès, Barthélémy Alain, Prévost Florian, Lombard Laurent, Zaouter Yoann, Druon Frédéric, Georges Patrick
Opt Express. 2015 Mar 9;23(5):5406-16. doi: 10.1364/OE.23.005406.
Active coherent beam combination using a 7-non-coupled core, polarization maintaining, air-clad, Yb-doped fiber is demonstrated as a monolithic and compact power-scaling concept for ultrafast fiber lasers. A microlens array matched to the multicore fiber and an active phase controller composed of a spatial light modulator applying a stochastic parallel gradient descent algorithm are utilized to perform coherent combining in the tiled aperture geometry. The mitigation of nonlinear effects at a pulse energy of 8.9 µJ and duration of 860 fs is experimentally verified at a repetition rate of 100 kHz. The experimental combining efficiency results in a far field central lobe carrying 49% of the total power, compared to an ideal value of 76%. This efficiency is primarily limited by group delay differences between cores which is identified as the main drawback of the system. Minimizing these group delay issues, e.g. by using short and straight rod-type multicore fibers, should allow a practical power scaling solution for femtosecond fiber systems.
采用7芯非耦合、保偏、空气包层、掺镱光纤的主动相干光束合成，作为超快光纤激光器的一种单片式紧凑功率扩展概念得到了验证。利用与多芯光纤匹配的微透镜阵列和由应用随机并行梯度下降算法的空间光调制器组成的主动相位控制器，在平铺孔径几何结构中进行相干合成。在100 kHz重复频率下，对脉冲能量为8.9 μJ、持续时间为860 fs时的非线性效应抑制进行了实验验证。实验合成效率使得远场中心瓣承载总功率的49%，而理想值为76%。该效率主要受芯间群时延差异的限制，这被认为是该系统的主要缺点。例如，通过使用短而直的棒状多芯光纤来最小化这些群时延问题，应该能够为飞秒光纤系统提供一种实用的功率扩展解决方案。
