Void formation in glasses

Void formation as a result of a single tightly focused femtosecond pulse irradiation has been systematically studied in commercial optical-grade glasses of different composition. Correlations between the composition, mass density, glass transition temperature and Young modulus of glass with the void formation threshold have been revealed. The pulse energy necessary to form a void was found reciprocal to the amount of glass-forming oxide in the case of silicate, phosphate and borate glasses. The larger is the bond strength (the cohesion energy per bond) of the glass-forming oxide, the lower is the threshold energy of the pulse, at which the void is formed after a single pulse irradiation.