Understanding noise and coherence properties of supercontinuum generation in non-instantaneous liquid core fibers

超连续统产生（SCG）允许通过非线性光学效应分布电磁能量在定义的光谱域。一种特殊的有效方案依赖于高阶孤子在光纤中裂变成它们的基本对应物，这与色散波的发射有关。由于SCG源自非线性材料响应，因此对相位和振幅噪声具有较高的敏感性。这种敏感性在生成的光谱集合内施加变化，这对于需要使用单个光谱的应用可能是有害的。这就形成了研究生成光谱之间的相关性的需求，即SCG过程的相干性。在固体玻璃纤维中，对于更高的峰值功率或更长的脉冲，SCG从高度相干状态演变为非相干状态，从而通过孤子数定义了相干极限。这个极限基本上与固体玻璃材料的瞬时响应有关。在之前的项目中，在模拟中首次发现了具有液体芯的光纤在孤子数下允许高相干SCG的证据，只有固体玻璃系统提供非相干光谱。这种改进与液体核心非线性响应的非瞬时贡献有关，这种非线性响应是由分子过程引起的，而分子过程完全是由于液体环境而不存在于固体材料中。该项目的主要目标是了解非线性时间响应的非瞬时贡献对液体芯纤维中产生的超连续体相干特性的影响。该项目的目标是从理论和特别是从实验的角度研究噪声和一阶相关程度的合成光谱。具体的科学问题是，例如，混合时间响应对孤子裂变和色散波形成的影响，以及这些是否是相应物理的有效描述。另一个问题是目前使用的相干极限，初步迹象表明，液芯光纤概念可以突破这一限制，在更高的输入功率水平下提供相干SCG。总体而言，该项目旨在展示基于包含混合时间响应函数的波导平台的基于孤子的SCG相干性的新的非线性物理，这与需要单个光谱的应用高度相关。

Supercontinuum generation (SCG) allows distributing electromagnetic energy via nonlinear optical effects across defined spectral domains. One particular effective scheme relies on the fission of higher-order solitons into their fundamental counterparts within optical fibers being associated with the emission of dispersive waves. Since SCG originates from nonlinear material responses, it reveals a comparably high susceptibility to phase and amplitude noise. This susceptibility imposes variations within the ensemble of generated spectra, which can be detrimental for applications requiring using individual spectra. This forms a demand for studying the correlation between generated spectra, i.e., the coherence of the SCG process. Within solid glass fibers SCG evolves from a highly coherent into an incoherent state for higher peak powers or longer pulses, having led to the definition of the coherence limit via the soliton number. This limit is fundamentally associated with the instantaneous temporal response of solid glass materials. Within the preceding project first evidence that fibers with liquid cores allow for highly coherent SCG at soliton numbers solely solid glass systems deliver incoherent spectra was found in simulations. This improvement is associated with the non-instantaneous contribution to the nonlinear response of the liquid core, resulting from molecular processes that are solely due to the liquid environment and do not exist in solid materials.The main objective of the proposed project is to understand the impact of a non-instantaneous contribution to the nonlinear temporal response on the coherence properties of supercontinua generated in liquid core fibers. The project targets investigating noise and first-order degree of correlation within the ensemble of generated spectra both from the theoretical as well as in particular from the experimental perspective. Specific scientific questions are for instance the impact of a hybrid temporal response on soliton fission and dispersive wave formation and if these are valid descriptions of the corresponding physics. Another issue is the currently used coherence limit, with first indications suggesting that the liquid core fiber concept allows breaking through that limit, providing coherent SCG at higher input power levels. Overall, the project aims to demonstrate new nonlinear physics with respect to the coherence of soliton-based SCG based on a waveguide platform incorporating a hybrid temporal response function, which is highly relevant for applications that demand individual spectra.