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

特别是在中红外波长，光子应用要求光源具有与各自的先决条件相匹配的定制属性。光纤中基于孤子的超连续谱产生与初始窄带脉冲通过孤子裂变和色散波形成的非线性光谱展宽有关，最近被认为是在中红外波长产生所需光的一种很有前途的平台。尽管目前部署的超连续谱源取得了巨大的成功，但许多超连续谱源依赖于固体材料，特别是二氧化硅，这带来了各种不利的问题，如吸收有限的工作光谱区域、强烈的脉冲间波动、制造重复性不足、脉冲色散难以控制以及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液芯光纤中红外波段的孤子动力学和基于孤子的超连续谱产生，总体目标是在可调、灵活和集成的波导平台上解锁新的非线性物理。与许多固态材料相比，液体在中红外波段产生非线性光具有独特的优势，包括超过许多玻璃的透明窗口、极高的非线性折射率、以特殊方式定制和外部控制脉冲色散的潜力，以及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，后一特性允许产生在时间脉冲宽度上具有极高的脉冲间稳定性的超连续，典型的固态系统提供高度非相干的超连续。液芯光纤概念的另一个关键特征是其通过实时交换芯材、通过使用不同的液体或它们的二元混合物或通过施加诸如温度之类的外部影响来管理和操纵脉冲色散的潜力，从而允许实现具有局部改变的特性的复杂和定制的色散分布，否则很难实现这些特性。值得注意的是，液芯光纤产生的光子平台在组合各种类型的材料时提供了极大的灵活性，因为与通常使用的光纤拉伸工艺相比，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、时间分辨光谱、中红外频率计量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.