Improved quantum-dot-sensitized photorefractive polymer composite

Quantum dots have significant potential as photosensitizers with a range of possible surface structures and a variety of materials available. Quantum dots composed of a cadmium selenide (CdSe) core and a cadmium sulfide (CdS) shell have been combined with poly(N-vinylcarbazole) and electro-optic dye molecules to form a new photorefractive composite. The photorefractive nature of the material was demonstrated with a gain of 4 cm -1 in s-polarized asymmetric two-beam coupling. The photosensitizing ability of CdS nanoparticles in a photorefractive polymer composite has been previously only evident for larger applied fields. The diffraction efficiency of the current composite is a vast improvement over the quantum dot composite reported previously, with degenerate four-wave mixing yielding diffraction of 1.3% at 70V/μm. Analysis of the field-dependence of the space-charge field rise time reveals a zero-field dissociation efficiency of (3.6+/-0.5)x10 -5 . Other example quantum dot sensitizers are also under investigation.