Fluorescence of Eu3+ ions in TiO2 optical planar waveguides fabricated by the sol-gel method

In recent years, rare-earth-doped optical planar waveguides have attracted considerable attention owing to their potential use in the field of integrated optics. To this end, several processes have been employed to produce rare-earth-doped waveguides. Here, we report on the fluorescence of europium trivalent ions in TiO2 planar waveguides fabricated by using the sol-gel method and the dip-coating procedure. 2-mol % Eu3+ : TiO2 films were deposited on optically polished pyrex substrates. These films are 80 nm thick and their refractive index is ranging from 1.8 to 2.1 depending on the annealing temperature (100°C-600°C). The fluorescence of Eu3+ ions was obtained by the excitation in the 5D2 level with an Argon ion laser (wavelength = 465.8 nm). At room temperature, the fluorescence spectra were recorded for different annealing temperatures. A correlation was seen between the luminescence spectra and the structural evolution of the gel network. Indeed, it was observed that heat treatment increases the Stark splitting which partially removes the transitions J-degeneracy, indicating that Eu3+ ions occupy low-symmetry sites and are more embedded in the TiO2 gel (densification of the TiO2 gel). Furthermore, it was observed that increasing the annealing temperature entails a high frequency shift and a broadening of the [MATH] transition, which shows that Eu3+ ions occupy more distorted sites. these observations are in good agreement with results obtained by waveguide Raman spectroscopy

Polarized waveguide raman spectroscopy of the thorium phosphate xerogel thin films

Internet is commonly presented as an alternative to interlibrary loan and document supply by publishers. By integrating electronic resources, university libraries are making the challenge to perform access to scientific information for users efficiently. Traditional services based on paper are no more able to satisfy users. So, which services French university libraries are proposing to deal this challenge and meet their users needs ? The disciplinary we have choosen to answer to this question are sciences, techniques and medicine. So, it is important to precise that analysis we have bring in this article are not relevant for other disciplinary

Low Loss Sol-Gel TiO2 Thin Films for Waveguiding Applications

TiO2 thin films were synthesized by sol-gel process: titanium tetraisopropoxide (TTIP) was dissolved in isopropanol, and then hydrolyzed by adding a water/isopropanol mixture with a controlled hydrolysis ratio. The as prepared sol was deposited by “dip-coating” on a glass substrate with a controlled withdrawal speed. The obtained films were annealed at 350 and 500 °C (2 h). The morphological properties of the prepared films were analyzed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The optical waveguiding properties of TiO2 films were investigated for both annealing temperature using m-lines spectroscopy. The refractive indices and the film thickness were determined from the measured effective indices. The results show that the synthesized planar waveguides are multimodes and demonstrate low propagation losses of 0.5 and 0.8 dB/cm for annealing temperature 350 and 500 °C, respectively