Refractive index and absorption spectra changes induced by UV irradiation in lead silicate glasses

The negative refractive index changes were obtained in lead silicate glasses with different lead concentrations (from 30 mol% PbO to 50 mol% PbO) by irradiation with the frequency-quadrupled output of a Q-switched YAG laser (266 nm, 10 Hz repetition rate) at low energy density (50 mJ/cm2). The largest refractive index change Δn was −0.25 ± 0.04 in lead silicate glasses with 50 mol% PbO. UV-visible absorption spectra of the lead silicate glass with 43 mol% PbO were measured after exposure to the 266 nm laser beams with energy density from 50 mJ/cm2 to 350 mJ/cm2. The absorption coefficients in visible wavelength increased suddenly when the energy density of the laser beam was larger than a threshold value. This showed that the structural changes of lead silicate glasses were different after exposure to the 266 nm laser beam with different energy densities.