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Index patterning of photoreactive polymers

Photoreactive polymeric materials have been investigated under one-photon (linear) and two photon (non linear) absorption conditions. A selected chromophore, 4-(N,N-diphenylamino)phenyl benzoate, was covalently attached to different polymer backbones (polystyrene, polynorbornene and polysiloxane). It is shown, that the predominant photoreaction of the chromophore is a photo-decarboxylation (extrusion of CO2) both for two-photon and one-photon conditions. The large increase in refractive index, which results from this reaction, allows the optical patterning of the polymeric systems by conventional and two-photon radiation processes. The materials were investigated by ellipsometry, UV-VIS and FT-IR spectroscopy, FT-IR and phase contrast microscopy. Under two-photon conditions, three-dimensional index structures were inscribed in the polymers, which can be used as optical waveguides.