Color-center generation in silicate glasses exposed to infrared femtosecond pulses

The optical properties of silicate glasses under high-power, 850-nm femtosecond laser irradiation have been studied. Photoinduced processes occurred at irradiances well below the threshold for laser-induce damage. Laser spectral line broadening leading to supercontinuum generation in the visible and UV spectral regions was observed in all the glasses studied. Color-center generation and intrinsic luminescence were found in bore-silicate and alkali silicate glasses. It is believed that these processes result from linear and two-photon absorption of the short-wavelength component of the supercontinuum, causing ionization of the glass matrix. No color-center absorption in the visible region was observed in fused silica at irradiances up to the laser-damage threshold. (C) 1998 Optical Society of America.