Photo-induced birefringence in DR1-doped sol-gel silica and ORMOSILs thin films

Photo-induced birefringence has been measured by a pump-probe experiment in pure silica and ORMOSILs (ORganically MOdified SILanes) thin films contain ing Disperse Red I (DR1). The films are obtained via the sol-gel process us ing TEOS, GLYMO and ICPTEOS as precursors. Two characteristic relaxation ti mes have been estimated for the relaxation of the birefringence: a short ti me, related to the Cis --> Trans isomerization of the dye molecule, which d oes not depend on the hosting matrix, and a longer time, due to the angular diffusion towards the isotropy, strongly sensitive to the chemical bonding of the DR1 molecule with the host. (C) 2000 Elsevier Science B.V. All righ ts reserved.