Infrared femtosecond laser pulse-induced permanent reduction of Eu3+ to Eu2+ in a fluorozirconate glass

We report what is believed to be the first observation of permanent photureduction of Eu3+ to Eu2+ in transparent and colorless Eu3+-doped fluorozirconate glass at room temperature, using an infrared femtosecond laser. Difference absorption and electron-spin-resonance spectra of the glass before and after laser irradiation showed that a portion of the Eu3+ ions in the focused part of the laser inside the glass were reduced to Eu2+ ions after laser irradiation. It is suggested that Eu3+ ions act as electron-trapping centers, whereas active sites in the glass matrix act as hole-trapping centers, leading to the formation of Eu2+ ions. The observed phenomenon is inferred to be useful in the fabrication of optical memory devices with high storage density and waveguide-type micro-optical devices. (C) 1999 Optical Society of America.