Nanostructuring and lattice dynamics of materials by femtosecond lasers

Physically, the colour of an object is a complex result of its intrinsic surface properties, its transmission properties and its emission properties, all of which contribute to the mix of wavelengths in the light leaving the surface of the object. Structural colour is the production of colour by microscopically structured surfaces that disperse visible light. In nature, one of the best examples for structural colour are butterflies. Thanks to the periodicity found in the scales of their wings, iridescent colours arise not only because of pigmentation but also due to the interaction of light with such a photonic arrangement. Currently, there is a strong research orientation in the field of simulating such behaviour. Many attempts have been successful in replicating these nanoscale features and consequently, only the simplest and cheapest methods will prevail and eventually, be transferred to applications. The aim of this thesis is to demonstrate the control of the interaction of femtosecond laser pulses with matter for metal surfaces nanostructuring and colouring. An analysis of the specific physical mechanism of laser-matter interaction in the femtosecond regime is presented. The laser induced periodic surface structures (LIPSS) are identified along the generated surface textures. The analysis of the topography of the textured surfaces using different techniques (SEM, AFM) show the effectiveness of this method for generating multi-scale texturing. The different textures morphologies can be associated with different regimes of the laser-matter interaction (LIPSS, microstructures...). The evolution of periodic, self-assembly structuring is also investigated with the change in experimental parameters such as: laser polarisation and fluence, scanning speed of laser on the surface, number of laser passages and distance between adjacent scanning lines. By this investigation, we can control the structuring of aluminium surfaces and obtain iridescent or uniform colours (yellow, grey and black). Theses colours are reproducible under the same experimental parameters. Thus, new optical characteristics of structural colours are found and remarkable enhancement in the absorption of aluminium surface is obtained by nanostructuring (≈90% between 400-2000 nm). Moreover, a significant relationship between the total surface reflectance and laser-texture characteristics (morphology/topography and periodicity) is demonstrated. The chemical content analysis (EDX) of treated surfaces revealed an increase of aluminium oxide on the surface. An eventual role of defects in the oxide layer revealing the broadband absorption of the structured yellow surface of aluminium is suggested in a time-resolved transient reflectivity experiment. The similar chemical content of defects in all coloured surfaces leads us to attribute the major role to the structural colouring rather than to pigmentation. Thus, by changing the morphology of the surface we created yellow, grey and black colours. The femtosecond laser technology presents a powerful tool to study the temporal evolution of the relaxation dynamics of systems. We describe the construction and characteristics of a setup for recording of reflectivity/absorption spectra with a time resolution in the femtosecond domain. In addition, new experimental results on the exploration of high-temperature superconductivity are presented. These investigations are part of a larger project dealing with the femtosecond dynamics of Cooper pair condensates in superconductors.