Enhanced spectroscopic properties and Judd-Ofelt parameters of Er-doped tellurite glass: Effect of gold nanoparticles

Glasses with composition 70TeO(2)-20ZnO-10Na(2)O-0.5Er(2)O(3)-(x)Au are synthesized by melt-quenching technique. Their spectroscopic and optical characterizations are made. The presence of gold nanoparticles (Au NPs) with average size similar to 9 nm is confirmed from TEM micrograph. The value of E-dir is found to lie between 3.082 and 3.073 eV, while E-indir lies within 2.765 to 2.724 eV. The observed visible up-conversion (UC) emission under 779 nm excitation wavelength exhibits two bands centered at 546 nm (green) and 637 nm (red) in all samples. The glass with 0.4 mol% Au NPs shows dominant enhancement in the UC emission intensity of the order of 3.5 times for the green band (S-4(3/2) -> I-4(15/2)) and a weaker enhancement for the red (F-4(9/2) -> I-4(15/2)) band. The optical properties of the system are affirmed to depend strongly on the Au concentration in the dielectric medium. The absorption spectra consist of six bands attributed to absorption from ground state (I-4(15/2)) to I-4(13/2), I-4(11/2), I-4(9/2), F-4(9/2), H-2(11/2), and F-4(7/2) excited states. The structural reveals that the types of bonding and difference in electro-negativity can be manipulated by the presence of metallic NPs in glass matrix. Judd-Ofelt analysis asserts the increase in Omega(2) and Omega(6) parameters with the addition of Au NPs and the enhancement of green and red emissions. The enhancement is mainly attributed to large plasmonic effect of Au NPs. The proposed glasses can be nominated as potential materials for solid state laser developments. (C) 2013 Published by Elsevier B.V.