Optical Characteristics of Erbium-Doped SiO<sub>2</sub>/PVA Electrospun Nanofibers

Abstract

This paper reports on the fabrication and optical characteristics of erbium-doped silica/PVA nanofibers via sol gel and electrospinning techniques. Silica glass, PVA (polyvinyl alcohol) and SiO2/PVA composites displayed 85% to 90% transparent across 300 2000 nm wavelength range. The transmission spectra were measured using Cary 5000 UV-Vis-NIR spectrophotometer. Silica was synthesized using TEOS (tetraethylorthosilicate) as the precursor, while PVA solution comprised of 7.0 wt% in H2O. The compositional ratios of SiO2:PVA were from 6:4 to 1:9 and were doped with 0.2% to 0.6% of erbium. Suitable viscosities of Er3+-doped SiO2:PVA solutions were electrospun into mesh of long strands nanofibers. Morphological and material compositions in the nanofibers were analysed using FESEM (field-emission scanning electron microscopy) and EDX (energy-dispersive X-ray spectroscopy). Er3+-doped SiO2:PVA thin films were coated on fused-silica glass substrates via spin coating and were characterized for their refractive indices, optical transmission, and fluorescence using M-line technique, UV-Vis-NIR spectrometer and photoluminescence spectrophotometer, respectively. Lower ratios of silica to PVA solutions results in higher viscosities and produced more uniform nanofiber structures of diameters around 100 nm with lesser beads. The refractive index of 1.61 for Er-doped SiO2:PVA (1:9) thin film was measured with TE polarized 632.8 nm wavelength laser and the index shows to be higher for more content of PVA in the glass/polymer composites. The 0.4% of Er3+ in SiO2:PVA composite produced the highest luminescence intensity at 605 nm when excited with 514 nm source. Higher doping content caused ion clustering effect and leads to concentration quenching, hence decreased in the emission intensity.