Optimization of tunable laser glasses with the aid of dielectric relaxation and adsorption measurements E. Yariv a , R. Reisfeld a, * , Ts. Saraidarov a , E. Axelrod b , E. Rysiakiewicz-Pasek c , K. Wodnicka d a Department of Inorganic and Analytical Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel b Department of Applied Physics, The Hebrew University of Jerusalem, 91904 Jerusalem,Israel c Institute of Physics, Wroclaw University of Technology, W. Wyspianskiego 27, 50-370 Wroclaw, Poland d University of Mining and Metallurgy, 30-059 Krakow, Poland Abstract Therecentlydevelopedtunabledyelasersinthevisibleareobtainedbyincorporationofstablelaserdyesintoglasses 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,thesizeoftheporesandtheirdistributionintheglassareofmajorimportance.Inthispapertheinfluenceofthe 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 adsorp- tion)andmercuryporosimetryarecomparedwithdielectricmeasurementsandtheconclusionisthatthelatterprovide information about charge movement in glasses with the smallest pores. The water vapor from the atmosphere is ad- sorbedwithinthesmallestporesinamonolayerresultingintheformationofdipoles,thatcanbedetectedbydielectric measurements. Ó 2002 Elsevier Science B.V. All rights reserved. PACS: 81.20.F; 42.55.M; 61.43.G; 77.22.G 1. Introduction Since the incorporation of organic dyes into glassesbysol–geltechnologyhasbeenreportedand thepossibilityofthesystemrealized,atremendous number of papers on the subject have appeared in theliterature[1,2].Forinstance,ithasbeenshown that solid state laser can be prepared by incorpo- ratingopticallyactivemoleculesintoglassobtained bythesol–gelmethod.Theimpregnationofporous glassafterthebulkhasformedandtreatedathigh temperature with laser dyes, allows preparation of tunablesolidstatelasers[3–7]. The porosity of the glass is controlled by the way of preparation [8–15]. There are several pa- rameters that influence the hydrolysis and poly- condensation reactions, such as temperature, pH, type of alkoxide precursor, solvent, water and Journal of Non-Crystalline Solids 305 (2002) 354–361 www.elsevier.com/locate/jnoncrysol * Corresponding author. Enrique Berman Professor of Solar Energy. Fax: +972-2 658 5319. 0022-3093/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0022-3093(02)01115-8