Advanced high-power pulsed fibre laser systems and their applications
In this thesis, I report experimental studies towards power scaling of ultrashort fibre-based sources designed for applications including high average power femtosecond pulse generation and nonlinear frequency conversion. While the power produced by rare-earth doped fibre lasers operating in continuous-wave has dramatically increased within a few years to exceed the kilowatt level, pulsed fibre sources have been limited to tens of watts due to the onset of nonlinearities in fibre amplifiers. Therefore the aim is to manage fibre nonlinearities to achieve specific output properties at high average power. An innovative aspect of this work lies in the remarkable combination of telecom-grade semiconductor laser sources and high-power Yb-doped fibre amplifier technologies to produce short pulses at very high average power. Fibre nonlinear effects are often detrimental to the performance of fibre systems but can also provide an attractive tool to generate new useful wavelengths. The final part of this thesis describes efficient white light generation produced by a microstructure fibre pumped by the previously described green fibre source. Furthermore, I investigated a novel fibre source configuration for guide star application. The source I developed produced 1W at 589 nm through frequency doubling of 1178 nm radiation produced by pulsed Raman amplification in an Yb-doped fibre amplifier.