Fullerene derivatives embedded in hybrid sol-gel glasses: Nonlinear optical properties and optical limiting performances

Hybrid organic-inorganic materials are investigated as suitable materials f or inclusion of fullerene derivatives and for fabrication of laser protecti on devices. A specific synthesis has been developed in order to optimize no n-linear optical performances of fullerene derivatives. 3-glicydoxypropyltr ymethoxysilane has been used as an inorganic and organic network former to obtain the host material. The sol-gel synthesis consists of the hydrolysis and condensation in acidic conditions of the inorganic network. Epoxy polym erization has been achieved by using zirconium or BF3 alkoxides precursors. Bulk and multilayer materials doped with a fullerene derivative have been fabricated. They show good optical requirements: high fullerenes concentrat ion, high microstructural homogeneity, high laser damage threshold and high optical limiting efficiency. Optical limiting (OL) mechanisms have been in vestigated. The most effective in the sol-gel materials is the reverse satu rable absorption (RSA) one. However, different mechanisms, like non-linear (NL) scattering and NL refraction contribute to a different extent. Open- a nd closed-aperture OL and z-scan measurements on sol-gel samples show the c ontribution of NL scattering and NL refraction at 690 nm. Laser damage thre shold has been characterized as a function of the structure of the samples and of the optical configurations (f/66 and f/5).