Nonlinear optical performance of poled liquid crystalline azo-dyes confined in SiO2 sonogel films

• Published in: Journal of modern optics 2010-01, Vol.57 (1), p.65-73
• Main Authors: Torres-Zúñiga, V., Morales-Saavedra, O.G., Rivera, E., Flores-Flores, J.O., Bañuelos, J.G., Ortega-Martínez, R.
• Format: Article
• Language: English
• Subjects: Alignment; Atomic force microscopy; azobenzene; Chromophores; Exact sciences and technology; Frequency conversion; harmonic generation, including high-order harmonic generation; Fundamental areas of phenomenology (including applications); hybrid materials; Liquid crystals; Molecular structure; Networks; Nonlinear optics; Nonlinearity; Optics; Physics; Silicon dioxide; sol-gel; sonogel; thin films
• ISSN: 0950-0340; 1362-3044
• DOI: 10.1080/09500340903521843

The catalyst-free sonogel route was implemented to fabricate highly pure, optically active, hybrid azo-dye/SiO 2 -based spin-coated thin films deposited onto ITO-covered glass substrates. The implemented azo-dyes exhibit a push-pull structure; thus chromophore electrical poling was performed in order to explore their quadratic nonlinear optical (NLO) performance and the role of the SiO 2 matrix for allowing molecular alignment within the sonogel host network. Morphological and optical characterizations were performed to the film samples according to atomic force microscopy (AFM), ultraviolet-visible (UV-Vis) spectroscopy and the Maker-fringe technique. Regardless of absence of a high glass transition temperature (T g ) in the studied monomeric liquid crystalline azo-dyes, some hybrid films displayed stable NLO activity such as second harmonic generation (SHG). Results show that the chromophores were homogeneously embedded within the SiO 2 sonogel network, where the guest-host molecular and mechanical interactions permitted a stable monomeric electrical alignment in this kind of environment.