Self-organized light in multicore optical fibers: a route to scalable high-power lasers and all-optical signal processing

如今，光纤无处不在，并在从电信到高功率激光器的众多应用中得到了利用。在过去的十年里，出现了一种新型光纤，即所谓的多芯光纤。传统光纤只使用一个芯来传输光束，而MC光纤的特点是具有多个芯，每个芯都传输不同的光束。在每个核心中，光可以朝一个方向（向前）或相反的方向（向后）传播。当向前和向后光束同时存在时，我们指的是反向传播配置。本项目旨在研究反传播配置中不同核心光束之间的耦合动力学，并展示其在一些重要技术领域的应用，从高功率激光器到电信。团队成员进行的初步研究表明，当核心足够接近时，反传播配置引起的强耦合可能会发生，这样每个核心中的光束就会组织成规则的定义良好的模式。例如，每个芯内的前向光束和离开光纤的前向光束可能以相同的相位结束，而不管它们的初始相位如何。这些结果意味着在相干光束组合方面的自然应用，相干光束组合是指将多个独立光束组合在一起，从而在系统输出处获得具有高亮度和光束质量的单个光束的能力。值得注意的是，与目前最先进的解决方案不同，这里的光束组合是以“全光”方式实现的，也就是说，不需要使用复杂且功耗高的电子控制系统。事实上，是每个核中的光束本身由于相互耦合而自组织。在这个项目中，我们将设计、制造和测试定制的MC光纤，其中所提出的全光束组合将被用于构建下一代互联网的高功率光源和新型光学器件。此外，将开发一个通用的理论框架，不仅在光学中，而且在其他重要学科，如流体力学中也能找到应用。南安普顿大学光电研究中心（ORC）的一个多学科团队将负责该项目开发所需的广泛技能。ORC是世界领先的学术机构，拥有世界上最先进的纤维制造和实验实验室。

Optical fibers are nowadays ubiquitous and exploited in a multitude of applications, from telecommunications to high-power lasers. The last decade has seen the emergence of a new type of optical fiber, the so called multicore (MC) fiber. Unlike traditional fibers, where only a single core is used to carry the light beam, MC fibers are characterized by having a multitude of cores, each one carrying a different light beam. In each core, light can travel in one direction (forward) or in the opposite direction (backward). When forward and backward light beams are simultaneously present, we refer to a counter-propagating configuration. This project aims to study the coupling dynamics between beams of different cores in a counter-propagating configuration, and to demonstrate its application in some important technological areas, ranging from high-power lasers through to telecommunications.Preliminary studies carried out by the team members indicate that when the cores are sufficiently close, then strong coupling induced by the counter-propagating configuration may occur, such that the beams in each core organize themselves in to regular well-defined patterns. For example, the forward beams in each core and exiting the fiber may end up with the same phase irrespective of their initial phase. These results imply natural application in coherent beam combination, which refers to the ability to combine multiple independent light beams so as to obtain a single beam characterized by a high brightness and beam quality at the system output. It is worth noting that here, differently from current state-of-the-art solutions, beam combination is achieved in an "all-optical" way, that is to say without resorting to the use of complex and power-consuming electronic control systems. Indeed it is the beams themselves in each core that self-organize due to their mutual coupling. In this project we will design, fabricate and test bespoke MC fibers where the proposed all-optical beam combination is exploited to build high-power optical sources and novel optical devices for the next generation Internet. Moreover, a general theoretical framework will be developed that will find application not only in optics but also in other important disciplines, such as hydrodynamics.The wide range of skills required for the development of the project will be covered by a multidisciplinary team at the Optoelectronics Research Centre (ORC) of the University of Southampton. The ORC is a world leading academic institution with some of the most advanced laboratories for fiber manufacture and experiments available on the planet.