Ultra-short laser structuring of glasses: Predictive modeling insights
Résumé
Short and ultrashort laser pulses are particularly attractive for micro- and nano-structuring of glasses. Among the most promising applications, we can mention the formation of periodic and non-periodic 2D and 3D nanostructures that can be used not only in optics and photonics (optical memories, optical components, metamaterials, photonics crystals), but also in security, nanofluidics, medicine, etc.
Numerous experiments were focused on the investigation of the main features of ultra-short laser processing of dielectric materials [1-2]. It was demonstrated that a particular parameter window is often preferable to obtain the desired results and that different types of permanent material modification could be induced in glasses depending on the laser irradiation conditions. In these experiments, both single pulse and multi-pulse laser irradiation was used. However, many involved processes are still under discussion. To better control over the laser-based processing, a comprehensive and predictive modeling is developed and the results will be presented in this talk. In out modeling, first light propagation is modeled in a consistent way with possible non-linear material ionization due to the local field enhancement. Then, we consider the main photo-thermal processes taking place during ultra-short laser irradiation and thermo-mechanical wave propagation. As a result, spatiotemporal evolutions of temperature, pressure and density are calculated, which accompany the refractive index change over a broad range of timescales from femtoseconds to few microseconds as a function of laser parameters such as pulse energy, pulse duration, laser wavelength, numerical aperture, number of pulses and repetition rate. By applying this model, we study the role of the laser experimental conditions and the one of material properties. The physical processes such as thermo-mechanical effects and heat accumulation are also investigated and the parameter windows required for efficient laser treatment are explained.
References
[1]B. Poumellec, M. Lancry, R. Desmarchelier, E. Herve, F. Brisset, and J. Poulin, Opt. Mater. Express 3,1586 (2013)
[2] A. Rudenko, J-Ph. Colombier, T. E. Itina, From random inhomogeneities to periodic nanostructures induced in bulk silica by ultrashort laser, Phys. Rev. B93 (7), 075427.