Ultra-short Laser Interactions for Advanced Photonic Technologies.

International audienc

Ultra-short laser structuring of glasses: Predictive modeling insights

International audienc

Ultra-short laser structuring of glasses: Predictive modeling insights

International audienc

Laser–assisted periodic nanostructure formation in dielectric materials: formation mechanisms

International audienc

Well-controlled femtosecond laser inscription of periodic void structures in porous glass for photonic applications

International audienceWe report control possibilities over ultrafast laser-induced periodic void lines in porous glass. Instead of high intensity regime leading to filaments, multi-pulse irradiation with high repetition rate (500 kHz) and various writing speed is used here in a transverse geometry. The formation of a perfectly controlled periodic void structure is shown to rely on such parameters as laser energy per pulse and scanning speed. In particular, both the threshold energy required for this effect and the period of the fabricated void arrays are shown to rise linearly with the number of the applied laser pulses per spot, or with a decreasing writing speed. To explain these results, a thermodynamic analysis is performed. The obtained dependencies are correlated with linear energy losses, whereas the periodicity of the observed structures is attributed to a static energy source formation at the void location affecting both material density and laser energy absorption

On the role of nanopore formation and evolution in multi-pulse laser nanostructuring of glasses

International audienc

Femtosecond laser direct nanostructuring of ion doped porous dielectric and semiconductor films: mechanisms and applications

International audienceFemtosecond laser provides unique possibilities of the direct nanostructuring of both surfaces and highly localized volumes of dielectric materials. Here, we show extraordinary capacities of these lasers to create various surface and volume structures and to change their colors in mesoporous ion-doped matrixes. In addition to wide band gap dielectric materials, ion-impregnated semiconductor materials are used. Our experiments are performed by using several laser systems, configurations and beams. Firstly, two-beam interference set-up was used to produce grating-like structures. Secondly, a single scanning laser beams was used to produce periodic surface nanostructures. The roles of laser fluence, wavelength and polarization direction are evidenced. To better understand the mechanisms involved, a detailed multi-physical modeling is performed. Simulation results allow us to determine nanoparticle growth rate that relies not only on nanoparticle absorption, but also on the heat diffusion, photo-oxidation, and other reactions. The main laser parameters determine if the main mechanism is a thermal-activation or a photo-activation. Finally, the related applications in optics, photonics, catalysis and medicine are discussed

Ultra-Short Laser Structuring of Optical Materials in Volume

International audienc

Ultra-short laser-induced high aspect ratio densification in porous glass

International audienceMultiple ultra-short laser irradiation enabling direct writing of high aspect ratio barriers is used for structuring of nanoporous glass. Shape and morphology of laser-modified regions are examined, and high aspect ratio laser-induced material densification is founded. Experimental results are analyzed by modeling describing laser propagation, non-linear ionization and thermal effects. The role of laser focusing, laser energy and pulse number are examined. Several regimes are distinguished. Particularly, high-aspect ratio densified zones are obtained for the numerical aperture of 0.25, whereas either more symmetric densified regions or spherical cavities are shown to be formed for numerical aperture of 0.4. The resulting laser irradiation conditions required for deep and prolonged densification are explained by a lower ionization rate, leading to the under-critical free electron plasma density, longer filamentation and pulse-to-pulse elongation effects. Furthermore, filling of the porous glass with water is demonstrated to particularly extend the length of the densified region in depth. The presented study provides insights facilitating laser-based fabrication of barriers, membrane and patterns suitable for the environmental gas-phase analysis

Experimental and numerical study of laser-induced metal nanoparticle formation in thin porous films

International audienc