Effect of niobium oxide introduction on erbium luminescence in borophosphate glasses

The role of the addition of niobium oxide in large amount on the Er3+ emission properties at 1535 nm for excitation at 980 nm in borophosphate glass has been investigated. An increase of the emission, associated with a decrease of the lifetime of the 4I13/2 erbium level and a larger absorption cross section of erbium and ytterbium at 980 nm was evidenced. Changes induced on hydroxyl groups absorption with addition of Nb2O5 in glasses was clearly shown by IR Spectroscopy in the range 2500–3700 cm−1. The relationship between erbium luminescence at 1535 nm, Nb2O5 concentration and OH group nature in niobium borophosphate glasses has been discussed. A fluorination treatment, conducted to reduce the OH group content, has allowed the reduction of the absorption coefficient at 3000 cm−1 by half. Amplification measured at 1535 nm has confirmed the beneficial effect of the Nb2O5 introduction on the gain and has been found to be in accordance with the evolution of the luminescence properties.