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

TL;DR

This study investigates how electrostatic interactions between chromophores influence the nonlinear optical response of organic-inorganic sol-gel materials, demonstrating improved electro-optic coefficients through molecular and concentration optimization.

Contribution

It explores the effect of chromophore-chromophore electrostatic interactions in sol-gel systems, introducing a strategy to enhance NLO properties by controlling chromophore concentration and matrix composition.

Findings

Achieved a r33 coefficient of 15 pm/V at 633 nm for DR1 chromophore.

Obtained a r33 of 50 pm/V at 831 nm with an optimized chromophore.

Controlled electrostatic interactions improve nonlinear optical responses.

Abstract

In the last years, important non-linear optical 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 Tg 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 non-linear optical 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 TEOS (Tetraethoxysilane) concentration, we have obtained a r33 coefficient around 15 pm/V at 633 nm for the classical DR1 azo-chromophore and a r33 around 50 pm/V at 831 nm for a new optimized chromophore structure.