Photorefractive performance of a CdSe/ZnS core/shell nanoparticle-sensitized polymer

We report the photorefractive performance of a polymer composite sensitized by CdSe∕ZnS core/shell nanoparticles, and also comprising poly(N-vinylcarbazole) and an electro-optic chromophore. The nanoparticles are characterized by absorption and photoluminescence spectroscopy, elemental analysis, transmission electron microscopy, and powder x-ray diffraction. The electro-optic response of the composite is measured independently of the photorefractive effect by transmission ellipsometry. An asymmetric two-beam coupling gain of 30.6±0.4cm−1 is obtained, confirming photorefractivity. Degenerate four-wave mixing is used to assess photorefractive performance and, at a poling field of 70Vμm−1, yields a diffraction efficiency of 4.21%±0.03%, a holographic contrast of 3.05×10−4±1×10−6, a space-charge rise time of 25±2s, and a sensitivity of 4.7×10−5±4×10−6cm3J−1. These results constitute a significant improvement on the performance of previous nanoparticle-sensitized photorefractive polymer composites.