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Molecular Orientation by Two-Photon Isomerization: Towards 3 Dimensional Orientation Storage
Zouheir Sekkat, Makoto Maeda, Hidekazu Ishitobi and Satoshi Kawata

We present experimental evidence of two-photon photo-selection which is governed by a law in the fourth power of the cosine of the angle between the polarization of the excitation light and the two-photon transition dipole moment of the chromophore. We show that polarized two-photon excitation of photoisomerizable chromophores orients them in a nonpolar manner. We discuss the case of a diarylethene chromophore which is oriented by two-photon selective isomerization, and that of an azobenzene derivative which is selectively bleached by two-photon polarized excitation. The studies are done in thin films of poly(methylmethacrylate). We show that two-photon orientation exhibits birefringence under a reflection confocal microscope.

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