Upconversion luminescence of Al2O3-SiO2:Ce3+ glass by femtosecond laser irradiation

Near-infrared to visible upconversion luminescence was observed in a sol-gel processed Al2O3-SiO2 glass containing Ce3+ ions under femtosecond laser irradiation. The optical properties of the glasses reveal that the upconversion luminescence comes from the 5d-->4f transition of the Ce3+ ions. The relationship between the intensity of the Ce3+ emission and the pump power reveals that a three-photon absorption predominates in the conversion process from the near-infrared into the blue luminescence. The analysis of the upconversion mechanism suggests that the upconversion luminescence may come from a three-photon simultaneous absorption that leads to a population of the 5d level in which the characteristic luminescence occurs. (C) 2004 American Institute of Physics.