From Modeling-Based Understanding of Ultra-Short Laser Interaction with Glasses to Better Control Over Laser Nano- and Micro-Machining in Volume

Abstract : Propagation dynamics of ultrashort laser pulses in glasses can considerably affect femtosecond laser treatment of transparent materials. Numerous potential applications of bulk laser-induced plasmas range from laser micromachining to controlled temporary refractive index change or permanent damage in glasses. In particular, such structures as Bessel beam-induced long laser channels and laser-induced volume nanogratings will be analyzed. Recently, high angle Bessel beams delivered by femtosecond laser have been used for extremely high aspect ratio nanochannels generation and micro-structuring of glasses in volume. In particular, Bessel filamentation dynamics could be explained by strong plasma absorption, which occurs quasi-stationary in agreement with several experiments. The obtained results are analyzed as a function of laser parameters and cone angles. Furthermore, volume nanograting formation induced by femtosecond laser irradiation of fused silica with the presence of randomly distributed nanometric defects, such as holes or nanoparticles, is investigated numerically. It is shown that nanoplanes appearing at the interfaces between modified and unmodified areas elongate perpendicular to the laser polarization direction with a period significantly smaller than the incident irradiation wavelength. The characteristics of these nanoplanes are found to depend strongly on the concentration of the initial defects and on the irradiation wavelength in a good agreement with several experimental observations. The results of numerical simulations not only have facilitated laser micro- and nano- structuring of glasses, but also shed light on the physical origins of the observed structures. The possibilities of a control over femtosecond laser treatment of glass in volume are proposed.