Ag nanoparticles enhanced 2 μm luminescences of Ho3+/Tm3+ codoped bismuth germanate glasses

The Ho3+/Tm3+ codoped bismuth germanate glasses containing Ag nanoparticles (NPs) are synthesized by a chemical reduction method based on the conventional melting-quenching technique. The effect of concentration of Ag NPs on the 2 mu m emission is studied. The absorption band related to the surface plasmon resonance (SPR) of the Ag NPs is located in a range from 500 to 900 nm. Transmission electron microscopic image clearly reveals homogeneously dispersed Ag NPs with the sizes ranging from 5 to 10 nm. The luminescence spectra in a range of 1.7-2.3 mu m are collected. With the addition mass fraction of the AgCl up to 0.3%, the intensity of emission band of Ho3+ ions, centered at 2.03 mu m, is increased by 10 folds. The enhancement of 2 mu m luminescence is attributed to the enhanced local field induced by SPR of Ag NPs. The calculated absorption cross section and emission cross section are 0.491 x 10(-20) cm(-2) and 1.03 x 10(-20) cm(-2), respectively. When the gain coefficient p = 0.2, the positive gain would be realised.