Energy transfer and upconversion luminescence in Tm3+/Yb3+ co-doped lanthanum-zinc-lead-tellurite glasses

A series of Tin(3+)/Yb3+ co-doped lanthanum-zinc-lead-tellurite (TPZL) glasses pumped by a 980 nm laser diode (LD) were demonstrated to obtain a high efficiency of infrared-to-visible upconversion. Effects of PbO content on the thermal stability, structure and upconversion properties of Tm3+/Yb3+ co-doped TPZL glasses had been investigated. The efficient visible upconversion fluorescences corresponding to the (1)G4 -> H-3(6), (1)G(4), -> F-3(4) and H-3(4) -> H-3(6) transitions of TM3+ were observed under 980 nm excitation. The upconversion intensities of blue, red and near infrared emissions in Tm3+/Yb3+ co-doped TPZL glasses were obviously enhanced with increasing PbO content. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms had been evaluated by a proper rate equation model. Population density in different levels and coefficients of the energy transfer rate C-Di (i = 2, 4, 6) between Tm3+ and Yb3+ were estimated by fitting the simulated curves to the measured ones. The obtained three energy transfer coefficients C-D2, C-D4, and C-D6 were determined to be 5.7 x 10(-17), 1.3 x 10(-16) and 8.6 x 10(-17) cm(3)/s, respectively. (C) 2007 Elsevier B.V. All rights reserved.