Long-lasting phosphorescence in oxygen-deficient Ge-doped silica glasses at room temperature

We report on a novel phenomenon in oxygen-deficient Ge-doped silica glasses at room temperature. Irradiation of focused 120 fs laser pulses at 800 nm induced long-lasting phosphorescence with peaks at 290 and 390 nm for oxygen-deficient Ge-doped silica glass. The phosphorescence persisted for not less than 1 h after the removal of the irradiating light. The intensity of the phosphorescence at 390 nm increased with an increase in the concentration of oxygen-deficiency associated with Ge ions. Based on the time dependence of the intensity of the phosphorescence, the long-lasting phosphorescence in these glasses is considered to be due to the thermally activated electron–hole recombination at shallow traps.