Enhanced frequency upconversion in Er3+–Yb3+codoped heavy metal oxides based tellurite glasses

Highly efficient green up-conversion emission from fluoroindate glass nanoparticles functionalized with a biocompatible polymer

Up-conversion nanoparticles have garnered lots of attention due to their ability to transform low energy light (near-infrared) into high-energy (visible) light, enabling their potential use as remote visible light nano-transducers. However, their low efficiency restricts their full potential. To overcome this disadvantage, fluoroindate glasses (InF3) doped at different molar concentrations of Yb3+ and Er3+ were obtained using the melting-quenching technique, reaching the highest green emission at 1.4Yb and 1.75Er (mol%), which corresponds to the 4S3/2 → 4I15/2 (540-552 nm) transition. The particles possess the amorphous nature of the glass and have a high thermostability, as corroborated by thermogravimetric assay. Furthermore, the spectral decay curve analysis showed efficient energy transfer as the rare-earth ions varied. This was corroborated with the absolute quantum yield (QY) obtained (85%) upon excitation at 385 nm with QYEr = 17% and QYYb = 68%. Additionally, InF3-1.4Yb-1.75Er was milled and functionalized using poly(ethylene glycol) to impart biocompatibility, which is essential for biomedical applications. Such functionalization was verified using FTIR, TG/DSC, and XRD.

Fluorescence intensity ratio technique and its reliability

The present article reports the optical absorption and upconversion (UC) studies of 1.0 mol% Er3+/2.0 mol% Yb3+ doped/codoped glasses prepared by melt-quenching technique. The elements present and the composition of the prepared glass have been confirmed from XPS and XRF analysis respectively. Judd-Ofelt intensity parameters have been calculated using the absorption spectrum which is further utilized to predict the nature of Er_O bond, the transition probabilities, branching ratios and radiative lifetimes. The CIE study shows non-colour tunable and highly pure green emission (94.2%). The temperature-dependent UC emission spectra of the 2.0 mol% Yb3+ sensitized glass have been recorded at three different pump power densities to establish a reliable FIR based temperature scale. Furthermore, the Arrhenius fitting of the temperature-dependent spectra reveals low thermal quenching of green luminescence in the codoped glass.

Polymer/silica hybrid waveguide amplifier at 532 nm based on NaYF4:Er3+, Yb3+ nanocrystals

An optical waveguide amplifier, which can solve the problem of optical attenuation in optical network transmission, is the key technology to solve optical chip integration and optical interconnection. Here, to the best of our knowledge, we propose a novel polymer/silica hybrid waveguide amplifier at 532 nm for the first time. The research is of great significance to the improvement of short distance communication and visible light communication system. The waveguide amplifier was designed as an embedded structure based on NaYF₄:Er³⁺Yb³⁺ nanocrystals, which were synthesized by high-temperature thermal decomposition. When the input signal power was 0.1 mW, and the pump power was 300 mW, a relative gain of 4.3 dB was obtained on an 8 mm waveguide. This result is of great research significance to break the distance limit and make all-optical transmission a reality.

Effect of the Addition of Pb3O4 and TiO2 on the Optical Properties of Er3+/Yb3+:TeO2-WO3 Glasses

Heavy metal oxide tungstate-based tellurite glasses TeO2-WO3 (TW) containing Er3+/Yb3+ ions have been prepared by the melting and quenching method. The optical absorption and upconversion (UC) emission studies for the doped/codoped glasses have been performed. The effect of the addition of Pb3O4 and TiO2 to the Er3+/Yb3+:TW glass on its physical properties, optical absorption, and UC emission spectra under 980 nm/808 nm excitations has been studied. A significant enhancement in the UC emission intensity lying in the green and red region has been observed on introducing Pb3O4 and TiO2 into the Er3+/Yb3+:TW glass. The improvement in the UC emission intensity and full width at half maximum of the bands have been explained on the basis of energy transfer, local field correction factor, and Urbach energy. The non-color tunability in the color emitted from the prepared Er3+/Yb3+:TWPTi glass upon near-infrared (NIR) excitation at different pump power has been reported. Also, the color-correlated temperature and color purity have been measured under both NIR excitations.