Physical and Upconversion Photoluminescence Properties in Nd<sup>3+</sup>-Yb<sup>3+ </sup>Doped Lead Borate Glasses at 980 nm Excitation

Frequency upconversion (UC) photoluminescence (PL) in PbO-B 2 O 3 glass codoped with trivalent ions of neodymium (Nd 3+ ) and ytterbium (Yb 3+ ) is prepared by melt quench method. X-ray diffraction (XRD) and differential scanning carorimetry (DSC) done for structural and thermal studies. Physical properties as density, oxygen packing density, lanthanide ion concentration etc. calculated. Photoluminescence of the sample gives the information of spectral lines, corresponding to the Nd3+ transitions 4 G 9/2 4 I 9/2 (at 500 nm), 4 G 7/2 4 I 9/2 (at 550 nm), [ 4 G 5/2 ; 2 G 7/ 2 ] 4 I 11/2 (at 595 nm) and 4 G 7/2 4 I 13/2 (at 660 nm). The dependence of the UC intensity with the Yb 3+ concentration and the time behavior of the UC signal indicated the presence of two energy transfer (ET) pathways involving Nd 3+ -Yb 3+ pairs and Yb 3+ -Nd 3+ -Yb 3+ triads. Rate-equations for the population densities of the lanthanide energy levels were used to describe the dynamics of the UC emission and to determine the ET rates.