Enhanced infrared-to-visible frequency upconversion in Yb3+/Er3+ codoped Bi2O3-GeO2 glasses with embedded silver nanoparticles

We report the enhanced infrared-to-visible frequency upconversion (UC) in Yb3+/Er3+ codoped Bi2O3-GeO2 (BGO) glasses prepared using the melt quenching technique, with low concentration of AgNO3. Silver nanoparticles (NPs) with average size around 4 nm were observed using a high resolution transmission electron microscope (HR-TEM). The experiments were performed by exciting the samples with 980 nm diode laser in resonance with the 2F5/2 → 2F7/2 transition of Yb3+ ions. Emission bands were observed at 525, 545 and 655 nm that correspond to the following transitions of the infrared-to-visible frequency UC of Er3+: 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively. Enhancement of the UC luminescence efficiency up to 100% was obtained, attributed to the simultaneous influence of the increased local field in the vicinity of the silver NPs and the contribution of the Yb3+ → Er3+ energy transfer; it was also observed that the largest enhancement occurred for the band centered at 525 nm whose transition wavelength is closer to the silver NPs localized surface plasmon (LSP) wavelength. This is the first time that these effects are investigated for a bismuth germanate glass and demonstrate that Yb3+/Er3+ codoped BGO glasses with silver NPs can be used as efficient luminescent nanocomposite material for photonics applications.