Séminaire de l'INPHYNI: Maxime Cavillon

When ultrashort laser pulses are focused inside a transparent glass, they generate extreme light intensities, leading to nonlinear light absorption and the formation of an electron plasma. Subsequent electron-phonon coupling leads to a rapid temperature increase and pressure shock waves inside the glass matrix, resulting in various transformations like phase separation, crystallization, and cavitation. These changes create localized and permanent modifications in volume, influenced by laser conditions and glass composition. The modifications can achieve desirable optical properties, such as refractive index changes for waveguides and lenses, nonlinear crystal precipitation for frequency doubling, and polarization-oriented birefringence for geometric phase elements and optical sensors. The formation of nanogratings, due to glass self-structuring under light polarization, is particularly notable. This seminar will explore the mechanisms behind these transformations, focusing on nanograting formation and the influence of glass composition to it. It will also discuss how understanding these processes can improve the stability of laser-induced modifications in optical sensors used in extreme environments like aircraft engines and nuclear reactors.