| Popis: |
In this report we investigate the optical properties and energy-transfer upconversion luminescence of Ho 3+ - and Tb 3+ /Yb -codoped PbGeO 3 -PbF 2 -CdF 2 glass-ceramic under infrared excitation. In Ho 3+ /Yb 3+ -codoped sample, green(545 nm), red(652 nm), and near-infrared(754 nm) upconversion luminescence corresponding to the 4 S 2 ( 5 F 4 ) : 5 I 8 , 5 F 5 : 5 I 8 , and 4 S 2 ( 5 F 4 ) 57 , respectively, was readly observed. Blue(490 nm) signals assigned to the 52,3 : 5 I 8transition was also detected. In the Tb 3+ /Yb system, bright UV-visible emission around 384, 415, 438, 473-490, 545, 587, and 623 nm, identified as due to the 5 D 3 ( 5 G 6 ) : 7 F J (J=6,5,4) and D 4 : F J (J=6,5,4,3) transitions, was measured. The comparison of the up conversion process in glass ceramic and its gla ssy precursor revealed th at the former samples present much higher upconversion efficiencies. The dependence of the upconversion emission upon pump power, and doping contents was also examined. The results indicate that successive energy-transfer between ytterbium and holmium ions and cooperative energy-transfer between ytterbium and terbium ions followed by excited-state absorption are the dominant upconversion excitation mechanisms herein involved. The viability of using the samples for three-dimensional solid-state color displays is also discussed. Keywords: glass-ceramics, upconversion, rare-earth, luminescence, optical properties, glass |
