title: Photoinduced birefringence in nanostructured SiO2:DR1 sol-gel films.
abstract: Pump-probe photoinduced birefringence measurements were carried out in amorphous and in nanostructured sol-gel films with Disperse Red 1 (DR1) azochromophores embedded in a SiO2 matrix. X-ray diffraction (XRD) patterns determine the long-range nanostructure order of the films, exhibiting a lamellar nanostructure, with two different d-spacings, due to the presence during the sol-gel process of the Sodium Dodecyl Sulfate (SDS) or of the Cetyltrimethylammonium Bromide (CTAB) ionic surfactants. The photoinduced birefringence measurements were performed on fresh and on heat treated films as a function of the pumping time. The measurements give us information about the effect of the nanostructures on the azochromophores orientation dynamics. As a result, for the same azochromophores concentration, annealed nanostructured films exhibited the largest azochromophore mobilities but by the other side, amorphous films had the largest signal intensities. Besides, we established a phenomenological model for the analysis of the azochromophores orientation in the films as a function of the pumping time.
authors.affiliation: Departamento de Estado Sóldido, Instituto de Física, Universidad Nacional Autónoma de México, México, D.F.C.R 04510, Mexico.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Franco
authors.forename: Jorge A
authors.initials: JA
authors.lastname: García-Macedo
authors.forename: I G
authors.initials: IG
authors.lastname: Marino
authors.forename: P P
authors.initials: PP
authors.lastname: Lottici