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Title: Novel fibre optics : antiresonant guidance and twist-induced nonlinear propagation
Author: Chen, Yang
ISNI:       0000 0004 9356 3434
Awarding Body: Heriot-Watt University
Current Institution: Heriot-Watt University
Date of Award: 2019
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This thesis deals with the novel designs of polygonal-core hollow fibres based on antiresonant guidance. A triangular-core hollow fibre is demonstrated to allow a low leakage loss notably below 0.1 dB/m and a dispersion only ∼ 2.3 ps/(nm km) at the Er:YAG wavelength. The jacket tube width has been verified to play a role in preventing light escaping from fibre core. In contrast, another square-core hollow fibre designed for 1.55 μm realises a propagation loss 0.056 dB/m while the same design for 2.94 μm can guide with a loss only 0.023 dB/m. In this square-core design, both fibres assure that their losses of the fundamental modes almost approach less than 1/1000 of those of higher-order modes. An important universal geometrical ratio 0.845 between the effective circle-radius of cladding elements and the core radius is explained to better guide the single-mode design. Besides, this thesis depicts a general method to derive the nonlinear Schr ̈odinger equation of nonlinear propagation in twisted fibres. The third-order susceptibility tensor χ (3) in helical coordinates are involved. The feature of circularly-polarised propagation in twisted fibres is discussed. Coordinate transformation proves that the pulse amplitudes remain the same in both the laboratory and helical regimes. Nonlinear Schr ̈odinger equation shows strong reliance on the twist-induced orbital and spin angular momenta.
Supervisor: Biancalana, Associate Fabio Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available