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Hybrid organic-inorganic sol-gel coatings with high laser damage threshold

Nicolas Marchet ,  Philippe Belleville ,  Philippe Pren√© 

Commissariat à l'Energie Atomique (CEA), BP16, MONTS 37260, France

Abstract

For fifty years, a considerable effort has been and is still being directed to the production of optical coatings using liquid deposition route. The process investigated at CEA (French Commission for Atomic Energy) is mainly developed to prepare coatings using colloidal oxide-based and/or inorganic/organic hybrid materials in compliance with high power laser requirements.

The CEA megajoule-class laser so-called LMJ, needs 7,000-m2 of coated area onto 10,000 large-sized optical components. For use on highly-reflective (HR) component, a specific unstressed multilayer coating has been developed and deposited onto deformable adaptative substrate (Ph. Belleville, J. Sol-Gel Sci. & Tech.,19, 2000). This HR-coating is made of colloidal-based low index and hybrid-based high index thin film coatings with adaptable refractive index depending on the molar ratio of organic and inorganic compounds. Two metallic oxides (AlOOH and ZrO2) and six organic polymers have been selected and evaluated. The synthesis using sol-gel process of these oxides enables the control of the morphology and size of nanoparticles and suitable organic solvents have been chosen to allow organic polymer dissolution and preparation of uniform coatings. All materials have been selected regarding optical and laser damage properties using tests at 351 nm and 1053 nm wavelength.

Compatibilization of the hydrophilic surface of oxides nanoparticles with the hydrophobic organic polymers has been obtained using adapted functionalization of particles. We showed that it is possible to homogeneously disperse oxide nanoparticles in organic solvent using specific grafting agents like alkoxysilanes or carboxylic acids leading to time-stable sols. And also those high laser damage-resistant coatings can be prepared without any loss of optical properties. To demonstrate optical stacking feasibility, a multilayer coating has been prepared, showing optical reflectivity in good agreement with optical fitting model.

 

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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium A, by Nicolas Marchet
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 09:35
Revised:   2009-06-07 00:44