Ankündigung des Promotionsvortrags von Rafal Piotr Sopolla:
Soft-glasses have been attracting great interest for the fabrication of novel optical fibres, such as photonic crystal fibres (PCFs). This is because they offer extended ultraviolet to the midinfrared transmission and higher Kerr nonlinearities than the commonly used fused silica. Lead-germanate and tellurite oxide glasses can have extremely low water content and impurities, and so offer low absorption over their entire transmission window, making them ideal for generating supercontinuum (SC) light. Both glasses are fabricated in an in-house melting and casting facility, making it possible to specifically tailor their optical and mechanical properties.
The fibre fabrication is based on the ’stack-and-draw‘ method, which is the most flexible technique for fabricating microstructured fibres. To obtain rods and tubes for stacking a fibre preform, we implement an extrusion process using specially designed 3D-printed dies, thus enhancing design flexibility and precision of the fibre structures.
Precise control of the fibre cross-section with submicron accuracy provides a unique possibility to adjust the modal dispersion over a wide range of wavelengths, making the generation of new frequencies more efficient. A suspended-core microstructured fibre and a solid-core PCF were fabricated from germanate and tellurite glasses. The strong confinement of light in the glass and the high nonlinear susceptibility of the material allow generation of SC light covering 0.54-3.5 μm. The experimental results are in good agreement with the numerical simulations.
A long-standing challenge in SC generation is to generate broadband light in a single circular polarisation state. This work shows that an elegant solution is the use of a chiral PCF which exhibits circular birefringence. The fibre was made from fused silica and the permanent twist was created by spinning the fibre preform during fibre drawing. The theory and experiment confirm that the chiral PCF significantly outperforms the untwisted PCF in terms of polarisation properties.
(Vortrag auf Englisch)
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