Energy transfer and upconversion luminescence in Tm 3+/Yb 3+ co-doped lanthanum–zinc–lead–tellurite glasses

Abstract

A series of Tm 3+/Yb 3+ 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 Tm 3+/Yb 3+ co-doped TPZL glasses had been investigated. The efficient visible upconversion fluorescences corresponding to the 1G 4→ 3H 6, 1G 4→ 3F 4 and 3H 4→ 3H 6 transitions of Tm 3+ were observed under 980 nm excitation. The upconversion intensities of blue, red and near infrared emissions in Tm 3+/Yb 3+ 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 Tm 3+ and Yb 3+ were estimated by fitting the simulated curves to the measured ones. The obtained three energy transfer coefficients C D 2, C D 4, and C D 6 were determined to be 5.7×10 −17, 1.3×10 −16 and 8.6×10 −17 cm 3/s, respectively.