Supercontinuum generation in multimode optical fibres and waveguides

当高强度短脉冲激光通过光纤或平面波导传输时，它通过非线性过程经历了显著的光谱展宽。因此，单波长激光可以转换成宽带白光，即所谓的超连续谱。这种光源已经被用于一系列科学目的，例如被授予2005年诺贝尔物理学奖的精密光谱学。然而，对于大众市场的应用，例如在照明和图像投影方面，当前的系统提供的功率太低并且没有足够的能效。一种有希望的解决方案是使用更大芯径的光纤来实现高功率，并利用多模非线性效应来提高效率。然而，尽管人们已经很好地了解了单模光纤中的超连续谱产生，但对其对应的多模光纤却知之甚少。初步的实验表明了一系列新的和令人兴奋的效应，但到目前为止，这些更复杂的非线性系统在很大程度上还没有被开发出来。我们将进行详细的分析研究，并开发用于高效数值模拟的计算机代码。然后，我们将使用这些工具来彻底理解非线性多模脉冲传播的基本物理，并解释这些新的观测结果。最后，我们的结果将使我们能够设计用于复杂超连续谱的空间和光谱定制的光纤，但也将为其他高功率器件的物理研究提供新的见解，如大芯光纤激光器和放大器。

When high-intensity short-pulse laser light propagates through optical fibres or planar waveguides, it experiences significant spectral broadening through nonlinear processes. Thus, single-wavelength laser light can be converted into broadband white light, a so-called supercontinuum spectrum. Such light sources have already been used for a range of scientific purposes, for example for precision spectroscopy which was awarded the 2005 Nobel Prize in Physics. However, for mass-market applications, for example in illumination and image projection, current systems provide too low power and not sufficent energy efficiency. A promising solution is to use fibres of larger core diameters for high power and to exploit multimode nonlinear effects for enhanced efficiency.However, while supercontinuum generation in single-mode fibres is well understood, very little is known about its multimode counterpart. Preliminary experiments suggest a spate of novel and exciting effects, but so far these more complex nonlinear systems are largely unexplored.Here, we propose to develop a theoretical framework to model such complex systems. We will perform detailed analytical investigations and develop computer code for efficient numerical simulations. We will then use these tools to obtain a thorough understanding of the fundamental physics of nonlinear multimode pulse propagation and to explain these novel observations. Finally, our results will allow us to design fibres for spatial and spectral tailoring of complex supercontinua, but will also provide novel insights into the physics of other high-power devices such as large-core fibre lasers and amplifiers.