Eur. Phys. J. Appl. Phys. (2014) 67: 10502 DOI: 10.1051/epjap/2014140109 Effects of sol concentration on structural, morphological and optical waveguiding properties of sol-gel ZnO nanostructured thin films Mohand Tazerout, Azeddine Chelouche, Tahar Touam, Djamel Djouadi, Fares Boudjouan, Sebti Khodja, Salim Ouhenia, Alexis Fischer, and Azzedine Boudrioua