Symmetry of the all-optical orientation dynamics of an octupolar azo-dye salt

Optical patterning of the molecular order in dye doped polymers offers interesting and quite rich prospects. The generalization of the principles of holography to the recording of an interference pattern between mutually coherent fields of different frequencies, such as fundamental and second harmonic has been demonstrated to enable a full 3D polar control of the molecules. Together with exhibiting fairly large second order nonlinearities, donor–acceptor substituted azobenzene type materials were demonstrated to be very efficiently ordered materials under all-optical poling conditions. Photoinduced cis/trans isomerization results indeed in a free rotation of the molecule leading to an efficient molecular redistribution following the molecules selective polar excitation. In order to investigate the possible influence of the poling process on the resulting symmetry of the optically induced macroscopic susceptibility, a tetrahedral organotin azobenzene derivative was synthetized. All-optical orientation dynamics and symmetry of the second-order susceptibility χ(2) induced in PMMA rods doped with such a Td space-group molecule are reported and discussed. The molecular relaxation dynamics is shown to have a determining influence on the symmetry resulting from the all-optical poling process.