Photo-induced birefringence and polarization holography in polymer films containing spirooxazine compounds pre-irradiated by UV light

Photo-induced birefringence of spirooxazine (6'-piperidino-1,3,3-trimethylspiro[indolino-2,3'-[3H]naphtha-[2,1-b][1,4]oxazine)] in poly(methyl methacrylate) films pre-irradiated by ultraviolet light was investigated as a function of He-Ne laser (632.8 nm) pumping-beam intensity. A phenomenological model, taking photo-orientation and photoisomerization into account, is in good agreement with the measurements. This material exhibited a competing process between photo-orientation and photo-isomerization. The photo-orientation is predominant when the power density of He-Ne beam is lower; while the photo-isomerization is dominant at relatively high power density of He-Ne beam. In terms of these effects, a comparison between (s,s) and (s,p) holographic gratings optically recorded by He-Ne laser of 632.8 nm in this composite film pre-irradiated by UV light was also investigated. (C) 2004 Elsevier B.V. All rights reserved.