IR-to-blue and red wavelength upconversion in Pr3+:Y2SiO5 crystals

The IR-to-blue and red upconverted fluorescence in Pr3+:Y2SiO5 has been observed at room temperature with a tunable OPO laser excitation. The upconversion mechanism is investigated by means of the power dependence and the decay profile of upconverted fluorescence. It appears that excited state absorption (ESA) process using 1G4 energy level as intermediate state is responsible for the upconversion fluorescence.