Enhanced Photorefractivity in a Polymeric Composite Photosensitized with Carbon Nanotubes Grafted to a Photoconductive Polymer

We report on the photosensitization of photorefractive (PR) polymeric composites through the inclusion of multiwalled and singlewalled carbon nanotubes (CNTs), respectively, having poly(N -vinyl carbazole) (PVK) grafted to their surfaces. The PR nature of the holographic gratings was confirmed via the asymmetric exchange of energy in a two-beam-coupling (TBC) geometry, yielding TBC gain coefficients approaching 80 cm-1. In addition, in degenerate-four-wave- mixing experiments the prepared composites exhibited diffraction efficiencies as high as 60% and overmodulation voltages as low as ∼40 V/μm. These notable figures of merit indicate that the grafting of the PVK polymer to the various CNTs results in enhanced PR performance. The mechanism responsible for this enhancement in PR performance is investigated using a variety of experimental techniques