1,721,359 research outputs found
A trip in the history and evolution of ion-exchange process
No full textThe aim of this paper is to present a short review on some aspects and applications of ion-exchange, process with some considerations “old age” of this technique
Silica thin-films from perhydropolysilazane for the protection of ancient glass
Full text linkSilica coatings from polysilazane precursors were prepared to protect ancient glass from weathering. Polysilazane can be converted to silica by simple exposition to air or basic vapours and the properties of the synthesized film make this precursor a valuable choice to obtain solid, crack-free, highly adhesive and protective coatings. The coating is prepared starting from a Perhydropolysilazane precursor (20% PHPS in n-butyl ether) that allows to achieve high-quality thin-films of silica at room temperature. The obtained films are uncoloured, even in absence of strong heat-treatment. Perhydropolysilazane (PHPS) is a polymer of [-SiH2-NH-SiH2-]n units. When deposited on a soda-lime microscope slide, it reacts with atmospheric moisture (Si-H and Si-NH bonds are hydrolysed to Si-O) and a silica film is produced. The conversion to silica is completed in about 2.5 hours, using vapours of a 10 mol L-1 ammonia solution. The reaction is promoted with the application of a weak heat-treatment (45-50 °C), achievable using as heater a common tungsten filament lamp. The reaction of PHPS with atmospheric moisture produces a migration phenomenon of the mobile ions from the soda-lime glass to the film (in particular sodium, calcium and magnesium). The characteristics of the migration process vary according to the concentration of the precursor solution and the thickness of the film. Laboratory samples have been investigated by optical microscopy and surface techniques: XPS and SIMS. Preliminary evidences, obtained through the laser scanning confocal microscope (LEXT), on the application of such coatings at the surface of ancient stained glass are also discussed
A study on the periodicity of periodic poled lithium niobate crystals growth by the off-center Czochralski technique
No full textA systematic study on the role of each growth parameter in the PPLN period and the modification of the domain width across the crystal due to the growth process is presented. We focus our attention to the effect of the random errors in the domain boundary position on the SHG conversion efficiency and show a way of optimizing the growth process in order to achieve the highest SHG conversion efficiency and to establish the tolerances on the fabrication processes
Optical waveguides in lithium niobate: recent developments and applications
No full textThe state of the art of optical waveguide fabrication in lithium niobate is reviewed, with particular
emphasis on new technologies and recent applications. The attention is mainly devoted to recently
developed fabrication methods, such as femtosecond laser writing, ion implantation, and smart cut
waveguides as well as to the realization of waveguides with tailored functionalities, such as
photorefractive or domain engineered structures. More exotic systems, such as reconfigurable and
photorefractive soliton waveguides, are also considered. Classical techniques, such as Ti indiffusion
and proton exchange, are cited and briefly reviewed as a reference standpoint to highlight
the recent developments. In all cases, the application-oriented point of view is preferred, in order to
provide the reader with an up-to date panorama of the vast possibilities offered by lithium niobate
to integrated photonics
Primary ion implantation and recoil implantation effects in Cs depth profiling of thin metallic layers on LiNbO3
No full textDepth profiles obtained under Cs bombardment of samples of crystalline lithium niobate (LiNbO 3) covered with a thin layer of metal display some artifacts related to metal/LiNbO 3 interface effects. The altered yields of Li and Nb secondary ions in the first 50nm after erosion of the metal layer can be interpreted in terms of different stopping powers between metal and LiNbO 3. In this study, two typical samples are investigated and the artifacts are qualitatively explained by comparing experimental profiles and simulations performed with the transport of ions in matter code. The similarity between experiment and simulation suggests that the ballistic interpretation of the artifacts is appropriate
Model of the erbium ion exchange process in lithium niobate crystals
No full textA model based on the Nernst-Planck equations is discussed for the trivalent ion exchange process in lithium niobate crystals. Due to the material anisotropy and the different valence state of the exchanged species, a correction to the ion flux expression is considered to include the strain effects. The model is then used to describe the erbium ion exchange in both X- and Z-cut lithium niobate crystals. In this case, the dopant in-depth profiles measured by secondary ion mass spectrometry are well fitted by the theoretical profiles predicted by the model, supporting its validity. Since the model allows to predict the dopant profile into the substrate, it can be used to tailor the process parameters
High Resolution X-Ray Characterization of Sub-Micron Periodic Domain Structures in Lithium Niobate Crystals
No full textThe High Resolution X-Ray Diffraction technique in the reciprocal space mapping mode is exploited to study sub-micron periodic domain structures in lithium niobate crystals. Periodic satellite structure were detected around the reciprocal lattice points which carry information on the domain period and shape and also on the presence of lattice deformations. Moreover a pronounced diffuse scattering peak was observed, indicating the presence of a random displacement field possibly associated to the presence of randomly distributed structural defect
Characterization of waveguides obtained by proton exchange on a LiNbO3 substrate
No full textWaveguides obtained by proton exchange in LiNbO3 were characterized by Secondary Ion Mass Spectrometry and m-lines technique. Additional micro-Raman investigations evidenced marked changes in the spectra of the waveguide with respect to the substrate. This suggests that micro-Raman spectroscopy may constitute a direct non-destructive method to determine the depth of the exchanged layer, with a limit which is set by the diffraction-limited spot size
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