Upconversion luminescence of Er^(3+)/Yb^(3+)-doped halide tellurite glass is investigated experimentally upon 976-nm excitation. Three intense emissions centered at 525, 545 and 655 nm owing to the transitions (2)^H_(11/2) → (4)^I_(15/2), (4)^S_(3/2) → (4)^I_(15/2) and (4)^F_(9/2) → (4)^I_(15/2), respectively, are observed when pumping power is as low as 20 mW. The upconversion mechanisms and power dependent intensities are discussed. The high-populated (4)^I_(11/2) level is supposed to serve as the intermediate state responsible for the upconversion processes.

Er^(3+)-doped heavy metal borosilicate glasses were prepared using conventional melting and quenching method. The emission spectra of (4)^I_(13/2) → (4)^I_(15/2) transition were observed upon excitation at 974 nm and the lifetime of (4)^I_(13/2) level of Er^(3+) was measured. Based on these data, the fluorescence properties of Er^(3+) are investigated on the emission and gain characteristics at the 1.5 μm bands. In particular, the effect of relative heavy metal content on fluorescence properties is discussed.