Preparation of Silica and Titania Aerogels with Nonlinear Optical Properties

Abstract

The projects aims to synthesize new functional SiO2 and TiO2 aerogels with nonlinear optical properties by incorporation of nano-micro sized particles of ferroelectrical character into a transparent matrix composed of a nanostructured silica or titania aerogel. The objective is to measure frequency doubling (second harmonic generation, SHG) on aerogel samples without and with oriented ferroelectrical particles. On focussing a visible infrared laser beam (1064nm) onto a sample a visible green light (532nm) will be generated. A homogenous distribution of these particles in an aerogel is achieved by gelation under reduced gravity conditions. With gravitation the particles would settle during the gelation. These ferroelectrical particles are an important class of materials. They have a spontaneous electric dipole moment in zero electric field. These ferroelectric materials are for example BaTiO3, KNbO3, LiNbO3, LiTaO3. Because of the electric dipole moment the particle could be oriented in the silica matrix with an external electrical field. The orientation of the particles should happen during the gelation when the solution makes a phase transformation from the liquid into the solid phase. The SHG efficiency could be better, when the particles are oriented.