Supercontinuum generation in multimode optical fibres and waveguides

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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.