• Energy Research

Silica-tin dioxide thin films doped with Er3+ ions were fabricated and investigated. Different parameters such as heat-treatment temperatures, molar concentrations of SnO2 as well as Er3+ ions concentration were changed in order to obtain the best properties of presented thin films. Using several techniques, thin films were characterized and proved to be crack-free, water-free and smooth after a heat-treatment at 1200 °C. Aiming to application in optics, the transparency of thin films was also evidenced by transmission spectra. Based on the photoluminescence measurements, the mechanism of energy transfer from SnO2 nanocrystals to Er3+ ions was examined and discussed.

We show an electro-responsive 1D photonic crystal integrating electro-active plasmonic materials, whose dielectric function can be simply modulated by the application of an external bias.

One of the ways in which the cell efficiency of solar cells may be improved by better exploitation of the solar spectrum makes use of the down-conversion mechanism, where one high energy photon is cut into two low energy photons. When energy transfer between rare earth ions is used to activate this process, high emission and absorption cross sections as well as low cutoff phonon energy are mandatory. Glass-ceramics can be a viable system to fulfill these requirements. The main advantage of the glass-ceramic is to combine the mechanical and optical properties of the glass with a crystallike environment for the rare-earth ions, where higher cross-sections of the rare earth ion can be exploited. In the case of silica-hafnia system the glass ceramic is constituted by nanocrystals of HfO2, containing the rare earth ion, imbedded in the silica-hafnia host. Hafnia nanocrystals are characterized by a cutoff frequency of about 700 cm-1, so that nonradiative transition rates are strongly reduced, thus increasing the luminescent quantum yield of the rare-earth ions. In this work we investigated the Tb3+/Yb3+ energy transfer efficiency in a 70SiO2-30HfO2 glass-ceramic waveguide in order to convert absorbed photons at 488 nm in photons at 980 nm. The energy transfer efficiency was estimated as a function of the Tb3+/Yb 3+ molar ratio as well as of the total amount of rare earth ions. A transfer efficiency of 38% was obtained for Tb3+/Yb3+ = 0.25 mol and a rare earth content [Tb+Yb]/[Si+Hf] = 5% mol.

Glass-ceramics are nanocomposite materials which offer specific characteristics of capital importance in photonics. This kind of two-phase materials is constituted by nanocrystals embedded in a glass matrix and the respective composition and volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramic. Among these properties transparency is crucial, in particular when confined structures, such as dielectric optical waveguides, are considered, and several works have been devoted to this topic. Another important point is the role of the nanocrystals when activated by luminescent species, as rare earth ions, and their effect on the spectroscopic properties of the glass-ceramic. The presence of the crystalline environment around the rare earth ion allows high absorption and emission cross sections, reduction of the non-radiative relaxation thanks to the lower phonon cut-off energy, and tailoring of the ion-ion interaction by the control of the rare earth ion partition. Fabrication, assessment and application of glass-ceramic photonic systems, especially waveguides, deserve an appropriate discussion which is the aim of this paper, focused on luminescent glass-ceramics. In this work, a brief historical review, consolidated results and recent advances in this important scientific and technological area will be presented, and some perspectives will be outlined.

Flexible glass photonics is a cutting-edge technological and scientific research field that, thanks to a very broad spectrum of applications, has tremendously grown during the last decade and is now a strategic topic. Here, we present the results of the spectral transmittance and reflectance of a 10-layer SiO2/TiO2 1D photonic crystal deposited on a flexible polymeric substrate under different bending conditions, obtained with a home-made adjustable sample holder.

We measure and model the complex dielectric response of indium tin oxide films fabricated by nanocrystal deposition and sintering.

The unique properties of the Eu3+ ion make it a powerful spectroscopic tool to investigate structure or follow processes and mechanisms in several high-tech application areas such as biology and health, structural engineering, environment monitoring systems and quantum technology, mainly concerning photonics. The traditional method is to exploit the unique photoluminescent properties of Eu3+ ions to understand complex dynamical processes and obtain information useful to develop materials with specific characteristics. The objective of this review is to focus on the use of Eu3+ optical spectroscopy in some condensed matter issues. After a short presentation of the more significant properties of the Eu3+ ion, some examples regarding its use as a probe of the local structure in sol–gel systems are presented. Another section is devoted to dynamical processes such as the important technological role of nanocrystals as rare-earth sensitizers. The appealing effect of the site-selection memory, observed when exciting different sites into the 5D1 state, which the 5D0 → 7F0 emission band reflects following the sites’ distribution, is also mentioned. Finally, a section is devoted to the use of Eu3+ in the development of a rare-earth-based platform for quantum technologies.