Optical breakdown-driven mesostructure in bulk of soda-lime glass

• Optical breakdown in soda-lime glass
• Formation of localized mesoscopic crystalline structure
• Demonstration of shock-loaded phase transition by laser breakdown
• Presence of cristobalite and stishovite; high-temperature and high-pressure, respectively, polymorphs of silica

A study of structural changes in soda-lime glass irradiated with a tightly focused nanosecond laser pulse is presented with center on the material area strongly affected by pressure of a shock wave and the induced temperature. Different forms of microscopy, together with photoluminescence and Raman spectroscopy were used in characterization of the structural transitions induced by the optical breakdown in the bulk of soda-lime glass. Inspection of the irradiated region and its vicinity confirmed existence of an elongated void surrounded by a shell of densified material and the outer cracks. Laser-induced material densification was also identified by μ-Raman spectroscopy. High-resolution transmission electron microscopy (HRTEM) of the shock-affected region revealed nano-crystallization. Nanocrystals (crystallites) with an average diameter of 4–5 nm were precipitated in a matrix of densified glass and formed in this way a mesoscopic phase embedded in an amorphous host medium. This phase was spatially limited to a layer with a thickness of 100–150 nm at the shell/void interface.