Ž . Thin Solid Films 322 1998 238–244 Waveguiding properties of CdS-doped SiO –TiO films prepared by 2 2 sol–gel method S. Juodkazis a, ) , E. Bernstein a , J.C. Plenet a , C. Bovier a , J. Dumas a , J. Mugnier b , J.V. Vaitkus c a Departement de Physique des Materiaux, UniÕersite Claude Bernard Lyon I, UMR 5586, 43 BouleÕard du 11 NoÕembre 1918, ´ ´ ´ 69622 Villeurbanne Cedex, France b Laboratoire de Physico–Chimie des Materiaux Luminescents, UniÕersite Claude Bernard Lyon I, UMR 5620, 43 BouleÕard du 11 NoÕembre 1918, ´ ´ 69622 Villeurbanne Cedex, France c Semiconductor Physics Department, Vilnius UniÕersity, Sauletekio 10, 2040 Vilnius, Lithuania Received 14 May 1997; accepted 7 October 1997 Abstract Ž . Ž . We report on the preparation of SiO 20% –TiO 80% planar waveguiding layers by dip-coating technique. The layers are formed 2 2 Ž . from originally prepared sol with the added CdO and the subsequent precipitation of CdS nanocrystals NC during H S treatment. The 2 initial sol doping up to 92 wt.% was reached. The determination of the refractive index and thickness of waveguiding layer by m-line spectroscopy is presented. The porosity of film is evaluated. Influence of carbon contamination of the layer’s pre-surface area on the waveguiding properties is discussed. The possibilities of surface relief gratings as efficient input and output light couplers are demonstrated. q 1998 Elsevier Science S.A. All rights reserved. Keywords: Cadmium sulphide; Clusters; Optical properties 1. Introduction wx The interest in sol–gel derived glasses 1 doped by Ž . nanocrystals NC is supported by the technological sim- plicity of preparation and the prospective facility to achieve wx remarkably higher doping concentrations 2 than in fused wx glasses where the usual ones are up to few percent 3. Other distinctive features of sol–gel derived films as well as bulk materials are the low elaboration temperatures Ž . lower than 773 K . The high intensities of optical excita- w x tion are supported without photodarkening 4,5 due to the matrix surrounding NC in comparison to the semiconduc- tor doped glasses prepared by fusion. All these data sug- gest the interest in the experimental and theoretical investi- gations of such systems. ) Corresponding author. Institute of Material Science and Applied Physics, Vilnius University, Sauletekio 10, 2040 Vilnius, Lithuania. E-mail: saulius@dpm.univ-lyon1.fr. As far as the NC are grown in thin layers formed by an wx increasing number of techniques such as chemical 6, w x wx electrochemical 7,8 , ion plasma 9 deposition, there is an interest for the determination of optical properties by surface analysis methods and their modifications such as w x waveguiding or plasmon excitation 10 . The possibility has been demonstrated to launch the light into the waveguiding layer by the use of relief grating embossed directly on the surface of the sol–gel film w x 11,12 ; the applications of this technique for investigation of NC optical properties inside the films are still missing to our knowledge. The aim of our work was to demonstrate the possibility of preparing waveguiding layers by employing sol–gel Ž . Ž . derived SiO 20% –TiO 80% high refractive index 2 2 Ž . films supporting the waveguiding with the possibility for further modification of their optical properties by CdS nanocrystal precipitation. The other aim was to demon- strate the possibility of surface relief gratings as efficient input and output light couplers. 0040-6090r98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.