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Currently third harmonic generation (THG) in fibers is in focus of research, due to the prospects of enabling efficient generation of entangled photon triplets via the inverse, but spontaneous process. To date, microstructured and tapered fibers are the most prominent platforms to provide the high index contrast between the core and cladding material necessary to enable phase-matching (PM) to higher order modes (HOMs). Here, we employ a liquid core fiber (LCF) combining a silica cladding and a highly nonlinear core material, which can be temperature-tuned during operation [1].

Accurate dispersion management is key for efficient nonlinear light generation. Here, we demonstrate that composite-liquid-core fibers—fibers with binary liquid mixtures as the core medium—allow for accurate and tunable control of dispersion, loss, and nonlinearity. Specifically, we show numerically that mixtures of organic and inorganic solvents in silica capillaries yield anomalous dispersion and reasonable nonlinearity at telecommunication wavelengths. This favorable operation domain is experimentally verified in various liquid systems through dispersion-sensitive supercontinuum generation, with all results being consistent with theoretical designs and simulations. Our results confirm that mixtures introduce a cost-effective means for liquid-core fiber design that allows for loss control, nonlinear response variation, and dispersion engineering.

Optica 5(6), 695 - 703 (2018). doi:10.1364/OPTICA.5.000695, Liquid-core fibers offer local external control over pulse dispersion due to their strong thermodynamic response, offering a new degree of freedom in accurate soliton steering for reconfigurable nonlinear light generation. Here, we show how to accurately control soliton dynamics and supercontinuum generation in carbon disulfide/silica fibers by temperature and pressure tuning, monitored via the spectral location and the onset energy of non-solitonic radiation. Simulations and phase-matching calculations based on an extended thermodynamic dispersion model of carbon disulfide confirm the experimental results, which allows us to demonstrate the potential of temperature detuning of liquid-core fibers for octave spanning recompressible supercontinuum generation in the near-infrared., Published by OSA, Washington, DC

Liquid core fibers offer unique features such as hybrid nonlinear responses, wide transmission windows and real-time tuning capabilities. Here I will report on hybrid temporal solitons, coherent supercontinuum generation and real-time dispersive wave tuning.

We show theoretically that microstructured optical fibers filled with nonlinear liquids are capable of generating photon-pairs with highly tunable properties, suitable for applications in quantum spectroscopy and as sources of heralded single photons.