Enhanced near-infrared luminescence at 1.07 μm of Nd3+ doped PbCl2-Li2B4O7 glasses for solid state laser and optical fiber amplifier applications

Nd3+ doped PbCl2-Li2B4O7 glasses have been synthesized using melt quenching technique. XRD spectra reveals the signature of non-crystalline behavior of synthesized glasses. DSC studies reveal glass transition temperature and thermal stability parameter (Delta T) exhibit composition dependent trends and Delta T is as high as 114 degrees C. UV-Vis spectra contain eleven well-defined absorption peaks with five intense absorption bands centered at 527, 586, 750, 806 and 876 nm which are assigned to transitions from I-4(9/2) -> (4)G(7/2), [(4)G(5/2),(2)G(7/2)], [F-4(7/2), S-4(3/2)], [F-4(5/2), H-2(9/2)] and F-4(3/2) respectively. The maximum absorption cross section 1.139 x 10(-20) cm(2) of 806 nm pump level transition I-4(9/2) -> [F-4(5/2), H-2(9/2)] is comparable with maximum absorption cross section 1.149 x 10(-20) cm(2) of 586 nm hypersensitive transition I-4(9/2) -> [(4)G(5/2), (2)G(7/2)]. Near infrared emission spectra exhibit very high emission intensity at 1070 nm for F-4(3/2) -> I-4(11/2) transition along with two dominant emission bands at 904 and 1340 nm corresponding to F-4(3/2) -> I-4(9/2) and F-4(3/2) -> I-4(13/2) transitions. This high absorption and emission intensities are attributed to high degree of covalent environment of ligands surrounding Nd3+ ions. Bonding parameter, delta increase with Nd2O3 content which suggests dominance of covalency between Nd3+ ion and ligands. B-11 MAS NMR studies reveal that, the addition of Nd2O3 to Li2B4O7 converts diborate units into chain-like network structures such as charged trigonal borate units which is further supported by FTIR study. Two photon absorption coefficient shows linear relationship with optical band gap energy. Hence Nd3+ doped PbCl2-Li2B4O7 glasses with superior absorption and emission properties are found to be potential candidates for near-infrared solid state laser and optical fiber amplifier applications.