Light Source With Liquid Core

A light pulse is breaking up into solitons inside the optical fiber with a liquid core. (Source: IPHT)

Jena scientists from the Leibniz Institute of Photonic Tech­nology (Leibniz IPHT), the Fraun­hofer Institute of Applied Optics and Pre­cision Mechanics, the Friedrich Schiller Uni­versity of Jena, and the Helmholtz Institute Jena pumped a hybrid wave­guide with an ultrafast, intense laser pulse and produced a very broad light spectrum in the near and mid-infrared range (1.1 μm to 2.7 μm). Due to the unique charac­teristics of the liquid fiber core, the light pulse is broken up into solitons, a multitude of light waves with different wave­lengths. The solitons form the extremely broadband laser light that is indispen­sable as a super­continuum light source for appli­cations in medical imaging, measure­ment tech­nology, and spectro­scopy.

The coupled, ultrafast light pulse breaks up into solitons only due to non-linear inter­actions with matter in the optical fiber. In case of liquid core fibers, this means that the optical density of the liquid inside the core changes signi­ficantly with the inten­sity of the incident light. However, not many materials show nonlinear optical effects and, at the same time, exhibit sufficient light trans­mission in the infrared spectral range. Mario Chemnitz, scientist at Leibniz IPHT, explains the unusual effect as follows: “The fiber core is filled with carbon disul­fide, a liquid chemical compound with a very high refrac­tive index. If we now couple polarized light into the core, the carbon disul­fide molecules orient them­selves along the electro­magnetic field of the light. Due to this molecular orien­tation, the optical density depends on the intensity of the laser light.”

One unique feature of carbon disulfide is that the molecules orient them­selves with a certain time delay. If the incident laser light pulse is much shorter than the time that the molecules require for orien­tation in the optical field, the research scientists can observe a special, delayed dynamic of the resulting solitons. This was predicted back in 2010, but it was only now, the Jena scientists were able to provide experi­mental proof and an exact theo­retical descrip­tion of the processes. Mario Chemnitz describes this pheno­menon as an optical “memory effect” of the liquid. This unique charac­teristic of the liquid fiber cores reduces fluc­tuations in the spectral bandwidth of the super­continuum light source and makes liquid core fibers a more stable alter­native to the known broadband light sources based on optical fibers made from special glasses. (Source: IPHT)

Reference: M. Chemnitz et al.: Hybrid soliton dynamics in liquid-core fibres, Nat. Commun. 8, 42 (2017); DOI: 10.1038/s41467-017-00033-5

Link: Group Fiber Sensors (M. A. Schmidt), Leibniz Institute of Photonic Technology IPHT, Jena, Germany

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