Absorption Spectrum and Optical Parameters of Nd-Doped Barium Sodium Niobate Crystals

Nd-doped barium sodium niobate, (Ba2Na)1-x Nd x Nb5O15 (Nd:BNN), crystallizes with x=0.025 in a tetragonal system with a filled tungsten bronze structure and the point group 4 mm, conforming to the space group P4b m and z=2. The Curie temperature was 537±2°C. The lattice constants were a=b=1.2446(1) and c=0.3991(1) nm at room temperature. The measured absorption of Nd:BNN was compared to the Judd-Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric-dipole transitions of rare-earth ions on non-centrosymmetric sites demonstrates good agreement. An absorption band around 808 nm to match laser diode pumping is about three times broader than that of Nd-doped yttrium aluminum garnet crystal. The three intensity parameters Ω t were fitted as 5.677×10-20, 2.231×10-20, and 4.106×10-20 cm2 at t=2, 4 and 6, respectively. The fluorescence branch ratio at 1060 nm is 52.38%. The largest integrated emission cross section ∑(4 F 3/2→4 I 11/2) is 10.36×10-18 cm. These results indicate the crystal's potential applications as a practical laser material.