BLANC - Blanc

Elaboration de nouveaux matériaux hybrides à base de gels d'oxyde de titane pour applications en photonique – LaGel

Submission summary

Metal oxides play an important role in many areas of chemistry, physics and materials science. One of the most studied oxides in this respect is titanium dioxide because of several applications of functionalized or doped materials. The developed organic-inorganic hybrid materials are of special importance since they allow combining useful properties of both organic and inorganic components and can take benefit of interface between two-phases capable affecting electronic structure and electron transport. Recent studies show that optical proprieties of the hybrid materials can be considerably enhanced as compared to organic polymer materials, making them promising systems for photonic applications in forecoming years. The applied research of the sol-gel TiO2-based hybrids is related to high-refractive index coatings, optical waveguides, tunable F-P filters, micro-optical elements by direct electron-beam lithography, etc. A considerable effort of their development is currently produced in China and Japan. During last years two French teams (LIMHP and LCMCP) have demonstrated synthesis of new photosensitive organic-inorganic hybrid materials with inorganic TiO2 gel as active component, which replies on laser irradiation by a photo-chromic effect - darkening. These hybrids are mechanically stabile, transparent, allow optical-grade polishing, and conserve high photo-sensitivity inherent to wet TiO2 alcogels. They exhibit strong long-lived (months) absorption in the UV-visible-IR spectral range, leaving a transparency window in the near-IR. Considerable modification of the refractive index of the irradiated domains as well as their laser-induced bleaching have been observed. The photochemical mechanism of the relevant process offers advantages of reversibility and homogeneity of the irradiated domains on microscopic level. In particularly, no bubble formation due to material overheating or shock waves in the focal point is expected in these conditions. All these properties are theoretically predicted to be favorable for applications in 3D laser micromachining (such modification of transparent dielectrics is performed by femtosecond IR-lasers due to non-linear processes). The 3D-reversible optical recording in our hybrids with a special resolution of ~2 mm has been recently demonstrated by LZH (Germany). The key point of the current development concerns a detailed study of the elaboration process: this research has to be performed in the near future. Among the key factors, one can mention the extent of the metal-organic precursor modification, reactive fluids micromixing (including doping), inorganic network growth, and temporal synchronisation between different process stages (example: gelation/polymerization). Their control requires careful study of the process kinetics and the development of appropriate tools for in-situ measurements of local chemical composition and size of the participating clusters and larger nanometric units. The proposed project targets the process engineering : stable and reproducible elaboration of TiO2-gel based organic-inorganic hybrid materials with optimal useful proprieties in the laboratory-scale reactor, for applications in 3D laser micromachining. It includes three main tasks: (i) to propose a concept and to realize a sol-gel-hybrid reactor for the material elaboration (including doping) and the growth kinetic studies on molecular and nano and sub-micro scales (£1mm, which is domain relevant to many applications), (ii) (ii) to propose and realize cationic/anionic doping of these materials in order to introduce impurity levels within the energy range material transparency (E=3.1 eV that corresponds to L=800/2=400 nm) and to amplify the rate of two-photon electron transfer to Ti4+ (Ti:Sapphire laser, 800 nm) ; and (iii) to study optical properties and light-induced electronic transport in these materials in correlation with the elaboration process. A correlation between the elaboration process and material optical and electronic properties will be carefully studied. Working exchanges between partners will allow optimization of the material elaboration process. We target to assure reproducible and controlled material elaboration in sufficient quantities for studies. The developed laboratory-scale reactor can become a prototype of a large-scale reactor for a future commercial material elaboration. A theoretical modeling of the process kinetics, charge-transfer dynamics, and light propagation phenomena in these materials will complete the experimental studies. At the end of the project we target to demonstrate the 3D microstructuring by low-cost low-energy (nJ/pulse) Ti:Sapphire laser oscillator, that enables industrial applications (ex.: telecom.). The proposed study is based on strong and internationally recognized expertise of the participating teams in sol-gel process engineering (LIMHP), advanced hybrid material synthesis (LCMCP), and laser physics and optics (LPL).

Project coordination

Andrei KANAEV (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

UNIVERSITE DE PARIS XIII

Help of the ANR 440,000 euros
Beginning and duration of the scientific project: - 36 Months

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