Investigation of mid-IR soliton-based supercontinuum generation in liquid core fibers

特别是在中红外波长的光子应用需要具有定制特性的光源以匹配相应的先决条件。光纤中基于孤子的超连续谱产生，其与通过孤子分裂和色散波形成的初始窄带脉冲的非线性光谱展宽相关联，最近已被确定为用于在中红外波长处产生所需光的有前途的平台。尽管取得了巨大的成功，但目前部署的许多超连续谱源依赖于固体材料，特别是二氧化硅，这引起了各种不利的问题，例如吸收限制的操作光谱域，强脉冲间波动，制造再现性不足，难以控制脉冲色散和缺乏外部调谐孤子裂变过程的机会。本项目的主要目标是了解孤子该项目旨在研究液芯光纤中中红外波长下的非线性动力学和基于孤子的超连续谱产生，总体目标是在可调谐、灵活和集成波导平台的基础上开启新的非线性物理学。与许多固态材料相比，液体提供了在中红外波长下产生非线性光的独特优势，包括超过许多玻璃的透明窗口、特别高的非线性折射率、以特别的方式定制和外部控制脉冲色散的潜力以及在固体材料中不存在的独特的非瞬时非线性响应函数。如申请人所示，后一性质允许在时间脉冲宽度下产生具有特别高的脉冲间稳定性的超连续谱，典型的固态系统提供高度不相干的超连续谱。液芯光纤概念的另一个关键特征是其通过实时交换芯材料、通过使用不同的液体或它们的二元混合物或通过施加外部影响（例如温度）来管理和操纵脉冲色散的潜力，从而允许实现具有局部变化性质的复杂和定制的色散分布，这是非常难以实现的。重要的是要注意，液芯光纤产生光子平台，其在组合各种类型的材料方面提供了极大的灵活性，因为与通常使用的光纤拉制工艺相比，将液体引入光纤是直接的。除了揭示液芯光纤产生中红外超连续谱的潜力外，该项目的成果还将为未来中红外波长的非线性实验提供基础，包括量子光谱学，时间分辨光谱学，中红外频率计量学和频率梳的参数过程。

Particular at mid-IR wavelengths photonic applications demand light sources with tailored properties to match the respective prerequisites. Soliton-based supercontinuum generation in optical fibers, which is associated with the nonlinear spectral broadening of an initially narrowband pulse via soliton fission and dispersive wave formation, has recently been identified as a promising platform for the desired generation of light at mid-IR wavelengths. Despite its great success, many of the currently deployed supercontinuum sources rely on solid materials and particularly on silica, which give rise to various unfavourable issues such as absorption-limited spectral domains of operation, strong pulse-to-pulse fluctuations, insufficient fabrication reproducibility, hard-to-control pulse dispersions and a lack of opportunities for externally tuning the soliton fission process.The main objective of this project is to understand soliton dynamics and soliton-based supercontinuum generation at mid-IR wavelengths in liquid core fibers, with the overall aims to unlock new nonlinear physics on the basis of a tunable, flexible and integrated waveguide platform. In contrast to many solid state materials, liquids offer unique advantages for nonlinear light generation at mid-IR wavelengths, including transparency windows exceeding those of many glasses, exceptionally high nonlinear refractive indices, the potential for tailoring and externally controlling the pulse dispersion in extraordinary ways and a unique non-instantaneous nonlinear response function which is not present in solid materials. As shown by the applicant the latter property allows for the generation of supercontinua with exceptionally high pulse-to-pulse stability at temporal pulse widths typical solid state systems deliver highly incoherent supercontinua. Another key feature of the liquid core fiber concept is its potential for managing and manipulating the pulse dispersion by exchanging the core material in real-time, by using different liquids or binary mixtures of them or by applying external influences such as temperature allowing for the implementation of sophisticated and tailored dispersion profiles with locally changing properties that are exceedingly difficult to realize otherwise. It is important to note that liquid core fibers yield a photonic platform that offers great flexibility regarding combining various types of materials, as the introduction of liquids into fibers is straightforward in contrast to the typically used fiber drawing process. Besides uncovering the potential of liquid core fibers for mid-IR supercontinuum generation, the outcome of this project will provide a base for future nonlinear experiments at mid-IR wavelengths, including parametric processes for quantum spectroscopy, time-resolved spectroscopy, mid-IR frequency metrology and frequency combs.