DOCTORAL CANDIDATE
Jorge Guerrero

SUPERVISORS
Prof. Sébastien Février, Université de Limoges (UniLim)
Assoc. Prof. Alexis Giauque, Macquarie University (MQ)

Nonlinear optics, Optical Fibers, Fiber lasers, Soliton Dynamics, High-harmonic Generation, Femtosecond Laser Pulses

This PhD project focuses on the development of high-energy ultrafast laser systems operating in the mid-infrared (mid-IR) spectral region (3–5 µm) to enable deep ultraviolet (DUV) light generation through high harmonic generation (HHG) in solid-state materials.

Hence, focusing on the development of fibre-based ultrafast laser sources in the mid-infrared (mid-IR) spectral region, specifically targeting the generation of sub-100 femtosecond pulses with high peak power for nonlinear optical applications such as high harmonic generation (HHG) in solids.

To this end, it is proposed to develop a laser source delivering sub-100 fs pulses with microjoule level energy at wavelengths ranging from 2 µm to 3 µm based on rare-earth doped fibres (Er3+, Ho3+ or Dy3+) in silica or fluoride glasses. The seed laser source will deliver broadband femtosecond pulses originating from soliton dynamics in nonlinear fluoride fibres. It will be developed jointly by the partners based on custom components and fibres. The amplifier will exploit the chirped pulse amplification technique developed in the near-infrared. To this aim, the seed radiation will be stretched, pre-amplified, pulse-picked and finally boosted in rare-earth doped fluoride fibres (e.g. Er3+, Dy3+, Ho3+ depending on the wavelength of the seed). Great attention will be paid to amplify properly the pulse so as to reach (sub-)picosecond durations after the grating-based compressor. Then, a strategy based on post-compression in gas-filled hollow-core inhibited-coupling photonic crystal fibres will be applied to post-compress the high-energy pulse to sub-100 fs durations. Such ultrashort pulses with high energy (hundreds to thousands of nanojoules) will be exploited for high-harmonics generation in solid targets with the aim to provide a dense comb of harmonics by increasing the seed wavelength. This source will be well suited to vacuum ultraviolet – visible supercontinuum generation for electronic spectroscopy.

The project will involve a combination of numerical modelling and experimental implementation. Light propagation will be simulated to predict nonlinear pulse evolution in the chosen fibre geometries and to optimize input parameters. These results will inform the fabrication and tuning of the seed laser systems and the choice of nonlinear media. The optical components, including fibres and photonic crystal waveguides, will be custom-developed in collaboration with partner institutions and industry providers. Experimental results will feed back into the numerical models, allowing for continuous optimization of pulse characteristics.