Holographic Information Media Based on Azo-Polymers with Different Structures

Abstract

Abstract. Azobenzene polymer compositions are extensively studied now due to wide perspectives of their applications in optoelectronics and information technologies. Some possibilities of modifi cation of their properties by chemical methods are analyzed in the present work. These methods allow to improve information characteristics of the media. Electrooptical effect is investigated and possibilities of polarization sensitive holographic recording is demonstrated in copolymer octyl methacrylate with incorporated azo dyes and its complex with Co ions.Keywords: azobenzene, metallic polycomplexes, polymer composition, electrooptical effect, polarization holography. IntroductionFilms of polymeric compositions (PC) containing azobenzene dyes or azobenzene lateral groups [1,2] are of interest due to possibility of their use as optically active media [3,4], in particular as electrooptical or magnetooptical light controlling elements and polarization sensitive media for optical holographic recording. Induced polarization appears in the PC fi lms under infl uence of linearly polarized light which is absorbed by the azobenzene groups and causes changes of isomeric structures. The photoinduced polarization can be conserved at the room temperature during quite a long time. Changes of the polarization are possible under infl uence of external thermal or mechanical treatments, illumination with light and in external electric or/and magnetic fi elds. Rotation of the dipole moments happens in an external electric fi eld. Sensitization of this effect is possible by changing chemical structure of azobenzene groups or by using of different dopants. As it follows from numerous theoretical and experimental investigations [5,6] linearly polarized light is absorbed by the azobenzene groups resulting in changes of isomeric structure. Photoinduced anisotropy of the polarization appears in the fi lms due to changes of concentration of trans-and cis-isomers of the azobenzene groups. Rotation of the dipole moments is possible in an external electric fi eld involving changes of the conditions of interaction between light and PC. This is a fundamental reason of experimentally observed electrooptical effect.Since the mechanism of external electric infl uence is determined by the arisen forces orienting the dipole moments of the azobenzene compounds, one can suppose that introduction of metallic ions chemically connected to the polymer could strengthen the electrooptical effect. Also addition of magnetic nanoparticles into the PC could result in external magnetic fi eld infl uence on photoinduced optical anisotropy [7]. Physical properties of such doped PCs are not completely investigated so far as well as their information properties, i.e. the possibility of registration the diffraction grating, its maximal achievable diffraction effi ciency, its control by external electric and magnetic fi elds.Azobenzene containing PC are also considered as the perspective media for polarization holography [6,8] due to dependency of the photoinduced opt...