Regensburg 2004 – wissenschaftliches Programm
CPP 10.8: Vortrag
Montag, 8. März 2004, 17:30–17:45, H 38
Non-linear effects during inscription of azobenzene surface relief gratings — •Marina Saphiannikova1, Oliver Henneberg1, Thomas Geue1, Paul Rochon2, and Ullrich Pietsch1 — 1Institute of Physics, University of Potsdam, am Neuen Palais 10, 14469 Potsdam, Germany — 2Department of Physics, Royal Military College, Kingston, Ontario, Canada K7L 3N6
Surface relief gratings (SRGs) on azobenzene polymer films were inscribed using a pulse-like exposure of an Ar laser. A sequence of short pulses followed by much longer relaxation pauses was utilized for inscription process. The gradual development of the SRGs was probed by a He-Ne laser. Relative surface deformations were calculated from the scattering intensity of the first order grating peak. The SRG was found to grow far beyond the length of the pulse. So unusual behaviour can be considered as a non-linear one.
It is well known that the inscribing laser causes a trans-cis isomerization of azobenzene moieties. To explain the non-linear behaviour we have assumed that the polymer stress is proportional to the number of cis-isomers that could be calculated using a hole-burning model. Knowing the stress the polymer deformation can be derived with the help of one-dimensional viscoelastic analysis. The rate of trans-cis isomerization increases with the increase of intensity of the inscribing beam. In the absence of inscribing beam this rate is equal to the rate of thermal cis-trans isomerization. Fitting theoretical deformation curves to experimental data we have estimated both relaxation times.