Optical transitions and frequency upconversion of Er3+ ions in Na2O centerdot Ca3Al2Ge3O12 glasses

Er3+-doped and Er3+/Yb3+-codoped Na2O . Ca3Al2Ge3O12 glasses that are suita ble for use in optical waveguide devices have been fabricated and character ized. The density, the refractive indices, the optical absorption, the Judd -Ofelt parameters, and the spontaneous transition probabilities of the glas ses have been measured and calculated. Intense 1.533-mum fluorescence was o bserved in these glass systems under 798- and 973-nm excitation, and the qu antum efficiency was similar to 100%, Efficient upconversion luminescence a t 525, 547, and 659 nm at room temperature was also observed. At a pump int ensity of 1220 W/cm(2) at 798 nm, frequency upconversion efficiencies of 0. 98 x 10(-2) and 1.03 x 10(-2) were obtained for green and red emissions, re spectively. The standardized value for green emission is higher than those reported for lead germanate, lead tellurium germanate, silicate, and phosph ate glasses. Under 973-nm excitation, the enhancement of 1533-nm emission a nd visible upconversion fluorescence in Er3+/Yb3+-codoped glasses are confi rmed, and the sensitizing is due to efficient energy transfer from Yb3+ to Er3+. (C) 2001 Optical Society of America.