Super Broadband at Telecom Wavelengths From RE³⁺-Doped SiO₂-Ta₂O₅ Glass Ceramics Planar Waveguides

This paper reports on the preparation of Er³⁺/Yb³⁺/Tm³⁺, Er³⁺/Yb³⁺/Nd³⁺, and Er³⁺/Tm³⁺/Nd³⁺ triply doped and Er³⁺-doped SiO₂-Ta₂O₅ glass ceramic nanocomposites and active planar waveguides by the sol-gel process using the dip-coating technique as deposition method. The investigation of their structural, morphological, and luminescent properties using XRD, AFM, and photoluminescence analysis, are reported here. The XRD results showed the presence of L-Ta₂O₅ nanocrystals dispersed in the SiO₂-based amorphous host for all the nanocomposites and films. The rare earth ion (RE³⁺) doping concentration affected both the crystallinity, and the crystallite sizes of the Ta₂O₅ dispersed into SiO₂-Ta₂O₅ nanocomposites and waveguides. AFM characterization revealed crack free and smooth surface roughness and differences in viscoelasticity on the Er³⁺-doped SiO₂-Ta₂O₅ films surface, which allows the identification of Ta₂O₅ nanocrystals on the SiO₂ amorphous host. The Er³⁺ doped and triply doped SiO₂-Ta₂O₅ nanocomposites displayed broad- and super broadband NIR emissions with a FWHM up to 173 nm achieved in the telecom wavelengths. The lifetime of the ⁴I_13/2 emitting level of the Er³⁺-doped SiO₂-Ta₂O₅ waveguides is strongly dependent on Er³⁺ concentration and an emission quenching was negligible up to 0.81 mol%. The structural and luminescent investigations indicated that RE³⁺-doped SiO₂-Ta₂O₅ glass ceramics are promising candidates for photonic applications in optical devices operating in wide wavelengths at the telecom bands.