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

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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.