Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 6: Electronic+Optical Properties

CPP 6.4: Vortrag

Montag, 25. Februar 2008, 14:45–15:00, C 230

Investigation of grating formation in thin layers of an azobenzene-containing diblock copolymer — •Rafael Meinhardt¹, Sven Macko¹, Ansgar Draude¹, Yue Zhao², and Hilmar Franke¹ — ¹Department of Applied Physics, University of Duisburg-Essen, Duisburg, Germany — ²Département de chimie, Université de Sherbrooke, Sherbrooke, Québec, Canada

A diblock copolymer composed of poly{(ethylene oxide)45} and poly{[6-[4-(4-cynophenylazo)phenoxy]ethyl methacrylate]55} has been synthesized. Thin films (< 800nm) have been prepared from solutions in trichlormethane by gravity settling. Film thickness and changes of the refractive index anisotropy after homogeneous exposure were measured by m-line-spectroscopy and metal film enhanced leaky mode spectroscopy. In a conventional two beam holographic setup gratings with a lateral periodicity of 2000 nm have been generated using an argon ion laser (488nm). An exposure time of a few seconds was sufficient to obtain a grating with first order diffractions exceeding the transmitted 0th order. Different experiments with different polarization configurations have been performed with in situ measurements of the diffraction efficiencies which lead to diffraction efficiencies in the range of 40%. We will demonstrate the formation of a refractive index grating and a surface relief grating with different time constants and quantify their ratio. The formation of surface relief gratings particularly in the initial state has been investigated by performing AFM measurements. Applications for grating coupling, optical switching and tuneable gratings will be presented.