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Title: Periodic fibre devices for advanced applications in all-optical systems
Author: Shi, Jindan D.
ISNI:       0000 0004 2731 2194
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2012
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The main objective of this work is to investigate advanced applications of fibre gratings with the combination of nonlinear fibre optical effects, including the stimulated Raman scattering (SRS), Kerr effects, four-wave mixing (FWM) and second-harmonic generation. A Raman distributed-feedback (R-DFB) fibre laser formed in a passive optical fibre by using Raman gain is considered as the most promising route to generate a single-frequency and narrow-linewidth laser source at any wavelength given a proper pump source. In this thesis, the R-DFB fibre laser has been intensively studied both numerically and experimentally. Simulation results of centre π phase-shifted R-DFB fibre lasers show that the longer length of the DFB grating, the higher Raman gain coefficient and the lower background loss of the host fibre are always beneficial for achieving low threshold R-DFB fibre lasers. 30-cm long centre π phase-shifted R-DFB fibre lasers have been respectively demonstrated in two types of commercially available Ge/Si fibres of PS980 and UHNA4. Both un-polarised and linearly polarised CW Yb-doped fibre lasers at ~1.06 μm were used as the pump sources. The R-DFB fibre lasers are single-frequency operation at around 1.11 μm and have 3 dB linewidth less than 2.5 kHz; lasing thresholds down to sub-watt power levels; total output powers up to ~2 W; and total conversion efficiencies against incident pump power around 13%. Ultra-wide range (>110 nm) wavelength conversion by using FWM in these 30 cm-long R-DFB fibre lasers have been observed and up to ~-25 dB FWM conversion efficiency has been obtained. The nonlinearities and photosensitivity of several high-index non-silica glasses and fibres are also studied in order to incorporate fibre Bragg gratings (FBGs) with the highly nonlinear fibres to form R-DFB fibre lasers with lower thresholds. In particular, the Raman gain coefficient of a house-made tellurite glass fibre has been found to be ~35 times higher than the silica fibre and a SRS-assisted supercontinuum from ~1.1-1.7 μm has been observed in the fibre with a length of ~1.35 m by pumping at ~1.06 μm in the normal dispersion region of the fibre. Preliminary investigations into concatenating periodic poled silica fibres (PPSFs) to improve the frequency-doubling conversion efficiency are also presented.
Supervisor: Ibsen, Morten Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering