Nonlinear applications of step-index and microstructured soft-glass fibres

This thesis focuses on the potential of compound-glass, highly nonlinear, small-core fibres for use in nonlinear applications. Both fibres with a conventional step-index design and small-core holey fibres are considered. While the former technology is more mature, the latter represents the ultimate candidate, since it offers the flexibility of combining novel dispersion properties with a very high nonlinearity. With regard to holey fibre designs, small-core, compound-glass holey fibres with different core diameters and designs are considered for two different background materials: a commercially available lead-silicate glass and a bismuth-oxide based glass. Firstly, characterization measurements are performed on the fabricated holey fibres. The measurements reveal the advantages of each glass type and each fibre design, the ultra-high nonlinearity that can be achieved in such fibres and the potential of achieving simultaneously a novel dispersion profile and high nonlinearity. Nonlinear applications are then demonstrated for some of the fibres presented. In particular, the use of a lead-silicate holey fibre, having a dispersion-shifted profile, with a zero-dispersion wavelength lying close to the C-band is demonstrated in cross-phase modulation based wavelength conversion and switching applications in the 1.55 μm window. Both a co-polarized pump and probe scheme and a Kerr-shutter configuration are considered. For the same fibre, the stimulated four-wave mixing process for amplification and wavelength conversion applications in the C-band is thoroughly studied. Numerical simulations and experimental findings are combined to study the fibre performance, demonstrate its applicability to nonlinear wavelength conversion applications and identify future improvement objectives. The suitability of compound-glass holey fibres is also examined for the generation of correlated photons, through spontaneous four-wave mixing, and the generation of a broad supercontinuum by pumping at the convenient in terms of high power laser availability wavelength regions of 1.0 μm and 1.5 μm. The experiments presented in this thesis constitute the first nonlinear applications ever reported for dispersion-tailored, compound-glass holey fibres, clearly revealing their potential in fibre-based nonlinear applications. Nonlinear applications are also demonstrated for a commercially available, fiberised, bismuth-oxide based fibre with a step-index design. Using this fibre, an all-optical regenerator of Return-to-Zero picosecond pulses is realized at repetition rates of 10 and 40 Gb/s. The same fibre is also employed in an all-fiberised pulse compression scheme, which relies on nonlinear pulse propagation in the normal dispersion regime and enables the compression of picosecond pulses down to the femtosecond scale. In both applications, the ultra high nonlinearity of the compound-glass, step-index fibre results in reduced fibre-length and peak power requirements. The thesis concludes by addressing the issues concerning the practicality of compound-glass fibres and proposing potential future directions.EThOS - Electronic Theses Online ServiceGBUnited Kingdo