A novel upconversion TiO2-La2O3-Ta2O5 bulk glass co-doped with Er3+/Yb3+ fabricated by containerless processing

A spherical TiO2-La2O3-Ta2O5 glass co-doped with Er3+/Yb3+ has been fabricated using containerless processing in an aerodynamic levitation furnace. Green and red upconversion emissions centered at 531, 546 and 667 nm corresponding to the transitions Er3+: H-2(11/2) --> I-4(11/2), S-4(3/2) --> I-4(15/2) and F-4(9/2) --> I-4(15/2) have been obtained under the excitation of 980 nm laser at room temperature. The green emission is strong enough to be observed by naked eyes with pump power as low as 12.3 mW. It can be explained that the upconversion is based on a two-photon process by both the excited-state absorption and the energy transfer. Vickers hardness and fracture toughness of the sample are 7.7 GPa and 1.2 MPa.m(1/2), respectively. The sample shows high thermal stability with glass transition temperature as high as 786 degrees C. The presented Er3+/Yb3+ co-doped TiO2-La2O3-Ta2O5 bulk glass with upconversion luminescence could be employed as desirable host materials for all-solid-state laser. (C) 2011 Elsevier B.V. All rights reserved.