Effect of chromophore–chromophore electrostatic interactions in the NLO response of functionalized organic–inorganic sol–gel materials

• Published in: Optics communications 2001-10, Vol.198 (1), p.207-215
• Main Authors: Reyes-Esqueda, J, Darracq, B, Garcı́a-Macedo, J, Canva, M, Blanchard-Desce, M, Chaput, F, Lahlil, K, Boilot, J.P, Brun, A, Lévy, Y
• Format: Article
• Language: English
• Subjects: Absorption; Chromophore; Doped polymer; Electro-optic; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Integrated optics; Optical materials; Optics; Other nonlinear optical materials; photorefractive and semiconductor materials; Physics; Sol–gel
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/S0030-4018(01)01498-5

In the last years, important non-linear optical (NLO) results on sol–gel and polymeric materials have been reported, with values comparable to those found in crystals. These new materials contain push–pull chromophores either incorporated as guest in a high T g polymeric matrix (doped polymers) or grafted onto the polymeric matrix. These systems present several advantages, however they require significant improvement at the molecular level—by designing optimized chromophores with very large molecular figure of merit, specific to each application targeted. Besides, it was recently stated in polymers that the chromophore–chromophore electrostatic interactions, which are dependent of chromophore concentration, have a strong effect into their NLO properties. This has not been explored at all in sol–gel systems. In this work, the sol–gel route was used to prepare hybrid organic–inorganic thin films with different NLO chromophores grafted into the skeleton matrix. Combining a molecular engineering strategy for getting a larger molecular figure of merit and by controlling the intermolecular dipole–dipole interactions through both: the tuning of the push–pull chromophore concentration and the control of tetraethoxysilane concentration, we have obtained a r 33 coefficient around 15 pm/V at 633 nm for the classical DR1 azo-chromophore and a r 33 around 50 pm/V at 831 nm for a new optimized chromophore structure.