3-PHOTON UP-CONVERSION IN ER3+ DOPED CA3AL2GE3O12

Efficient upconversion fluorescence from an Er3+ center in Ca3Al2Ge3O1 2 has been observed, upon pumping with a single red dye laser. The mec hanism for the blue upconversion is either a sequential three-photon a bsorption or an energy transfer process depending on the laser energy being tuned on either the excited state absorption or the ground state absorption transitions. Owing to a double resonant excited state abso rption transition character, the three-photon blue upconversion effici ency is relatively high. (C) 1997 Elsevier Science B.V.