Optimization of tunable laser glasses with the aid of dielectric relaxation and adsorption measurements

The recently developed tunable dye lasers in the visible are obtained by incorporation of stable laser dyes into glasses prepared by the sol-gel method. In order that the lasers be photostable and more efficient it is essential that the dye molecules penetrate into the glass matrices in a unimolecular form and be protected from the surroundings. In this respect, the size of the pores and their distribution in the glass are of major importance. In this paper the influence of the various catalysts on the porosity of the glasses is presented. The pore sizes, their surface area, pore volume, pore size distribution and glass effective density are presented, and the solid state tunable lasers prepared under the optimal conditions are demonstrated. The results obtained by the conventional adsorption methods (water, nitrogen adsorption) and mercury porosimetry are compared with dielectric measurements and the conclusion is that the latter provide information about charge movement in glasses with the smallest pores. The water vapor from the atmosphere is adsorbed within the smallest pores in a monolayer resulting in the formation of dipoles, that can be detected by dielectric measurements.