Elastic excitations at laser-induced microstructuring: Analytical solutions

In this paper, we study the elastic excitations arising around the laser-induced focal zone during femtosecond laser microstructuring of glass-forming materials. Two problems of low and high laser pulse intensity associated with different laser microstructuring regimes are considered. The low intensity regime is suitable for a non-destructive smooth change in the refractive index in glasses. In the latter case of a high laser pulse intensity, hydrodynamic motion in the focal zone creates strong elastic excitations around this zone. Generation and propagation of elastic excitations around the focal zone are studied. In both cases, significant elastic excitations around the focal zone at distances significantly exceeding the size of the focal zone exist on the time scale of tens of nanoseconds. Laser-induced stress excitations reach several GPa around the focal zone. These excitations can irreversibly change the material around the focal zone. The analytical solutions for spherical geometry obtained in this work can be similarly constructed for cylindrical geometry. The obtained knowledge can be useful for a deeper understanding and optimization of laser microstructuring technologies.