Near infrared emission and multicolor tunability of enhanced upconversion emission from Er 3+ –Yb 3+ co-doped Nb 2 O 5 nanocrystals embedded in silica-based nanocomposite and planar waveguides for photonics

Abstract

This work reports on the Yb 3 þ ion addition effect on the near infrared emission and infrared-to-visible up conversion from planar waveguides based on Er 3 þ-Yb 3 þ co-doped Nb 2 O 5 nanocrystals embedded in SiO 2-based nanocomposite prepared by a sol-gel process with controlled crystallization in situ. Planar waveguides and xerogels containing Si/Nb molar ratio of 90:10 up to 50:50 were prepared. Spherical-like orthorhombic or monoclinic Nb 2 O 5 nanocrystals were grown in the amorphous SiO 2-based host depending on the niobium content and annealing temperature, resulting in transparent glass ceramics. Crystallization process was intensely affected by rare earth content increase. Enhancement and broadening of the NIR emission has been achieved depending on the rare earth content, niobium content and annealing temperature. Effective Yb 3 þ-Er 3 þ energy transfer and a high-intensity broad band emission in the near infrared region assigned to the Er 3 þ ions 4 I 13/2-4 I 15/2 transition, and longer 4 I 13/2 lifetimes were observed for samples containing orthorhombic Nb 2 O 5 nanocrystals. Intense green and red emissions were registered for all Er 3 þ-Yb 3 þ co-doped waveguides under 980 nm excitation, assigned to 2 H 11/2-4 I 15/2 (525 nm), 4 S 3/2-4 I 15/2 (545nm) and 4 F 9/2-4 I 15/2 (670 nm) transitions, respectively. Different relative green and red intensities emissions were observed, depending upon niobium oxide content and the laser power. Upconversion dynamics were determined by the photons number, evidencing that ESA or ETU mechanisms are probably occurring. The 1931 CIE chromaticity diagrams indicated interesting color tunability based on the waveguides composition and pump power. The nanocomposite waveguides are promising materials for photonic applications as optical amplifiers and WDM devices operating in the S, C, and L telecommunication bands; and as upconverter materials for visible upconversion lasers, biomedical applications, energy conversion for solar cells and others.

High-Quantum-Yield Upconverting Er3+/Yb3+-Organic–Inorganic Hybrid Dual Coatings for Real-Time Temperature Sensing and Photothermal Conversion

“…GeO 2 was dissolved in tetramethylammonium hydroxide (TMAH) solution, 25 wt % in H 2 O (Sigma-Aldrich), followed by the addition of acetylacetone (Sigma-Aldrich). In a separate container, tantalum ethoxide was diluted in the anhydrous ethanol followed by the addition of the dopant solutions, to obtain final concentrations of Er 3+ and Yb 3+ ions of 0.3 and 1.2 mol %, respectively, based on past experience. − The content of the two containers was mixed and the reactive medium was acidified with HNO 3 . The resulting solid, with 0.690:0.295:0.003:0.012 mol % of Ge:Ta:Er:Yb (labeled as Er 3+ /Yb 3+ -codoped GeO 2 –Ta 2 O 5 ), was annealed at 1100 °C for 8 h. The powder sample was compacted into a 5 mm diameter pellet.…”

Desenvolvimento de materiais nanoestruturados à base de SiO2-Nb2O5 preparados por uma nova rota sol-gel com aplicações em fotônica

“…Devido à sua alta seção de choque em 980 nm, o Yb 3+ absorve eficientemente a radiação eletromagnética neste comprimento de onda e, combinado à transferência de energia para outros íons TR, provoca um aumentando na intensidade de emissão nas regiões do infravermelho próximo e visível (MUSCELLI et al, 2015;AQUINO et al, 2016;ZMOJDA et al, 2016 …”

“…Em trabalhos anteriores de nosso grupo foi verificado que os alcóxidos utilizados como precursores na preparação de materiais dopados com íons TR por sol-gel foram muito sensíveis à hidrólise FERRARI et al, 2012;AQUINO, 2013;AQUINO et al, 2014;AQUINO et al, 2016). Alquier et al (ALQUIER et al, 1986) também reportaram a dificuldade em se preparar géis de pentóxido de nióbio devido à rápida hidrólise do precursor etóxido de nióbio.…”

Síntese e propriedades de materiais nanoestruturados luminescentes à base de Nb>sub<2>/sub<O>sub<5>/sub< e partículas SiO>sub<2>/sub<@Nb>sub<2>/sub<O>sub<5>/sub< dopados com íons lantanídeos para aplicação como marcadores ópticos

“…Este efeito tem sido verificado em trabalhos análogos no nosso grupo de pesquisa para nanocompósitos de sílica contendo nanocristais de oxido de nióbio (AQUINO et al, 2016;. No caso de nanocompósitos, foi verificado claramente que quando presente uma concentração elevada de oxido de nióbio, após o tratamento térmico a 900 C ocorre a formação de uma fase T bem cristalina, com uma excelente resolução nos picos e, portanto uma largura de pico estrita.…”