Dynamic orientational photorefractive gratings observed in CdSe/CdS nanorods imbedded in liquid crystal cells

A novel type of orientational photorefractive device, which consists of liquid crystals and semiconductor nanorods synthesized in our lab with a new seeded type growth approach has been designed and fabri- cated. The device has a symmetric layered structure, formed by a glass substrate, an indium-tin-oxide electrode (ITO), an HTAB aligning layer, a CdSe/CdS nanorods photoconductive layer, a NLCs film. In order to study the photorefractive and the orientational responses of this device we employed asymmetric two- beam coupling (TBC) to measure two-beam coupling gain under the influence of an applied electric field. A refractive index grating was written in the device in a holographic tilted configuration by two p-polarized laser beams at 514 nm. Self-diffraction of the writing beams and diffraction of a probe beam at 633 nm were measured. Our device revealed a very useful behavior in that the grating written in the sample is stable as opposed to the one without nanorods inclusion and it showed strong beam coupling effects. A very high TBC gain coefficient of over 350 cm?1 was achieved at a dc field applied of 3 V/lm. These results open up new possible applications for real-time image/signal-processing.