Characterization of Femtosecond Laser Filamentation in Soda-lime Glass

This paper demonstrates the characterization of femtosecond laser filamentation in soda-lime glass. We achieved femtosecond pulse filamentation of variable height and width by focusing the femtosecond laser beam in different layers inside the sample glass. The dielectric medium immediately before the target position increases the effective numerical aperture of the objective lens that causes the elongation of focal length of the laser beam in a tiny focal spot with high power density. As a result, high aspect ratio voids are engraved inside the glass samples. Furthermore, we investigate the characteristics of the fabricated voids and their dependence on the irradiation conditions of the laser beam and associated optical setup. The height and width of the voids are controlled by varying the laser power, numerical aperture & magnification of the objective lens, and width of the dielectric medium before laser focusing position. Using high power femtosecond laser pulse filaments, we fabricated very long voids inside the glass sample, which undergoes cleaving process with uniform mechanical pressure for smooth cutting of the glass substrate.