DYNAMIC ORIENTATIONAL PHOTO-REFRACTIVE GRATINGS OBSERVED IN CdSe/CdS NANORODS DOPED NEMATIC LIQUID CRYSTAL CELLS

Abstract

We observed an orientational photo-refractive effect in semiconductor CdSe/CdS nanorods-doped nematic liquid crystal cells homeotropically aligned. In order to study the photo-refractive and the orientational responses of this cell, we employed both asymmetric two-beam coupling (TBC) to measure two beam coupling gain under the influence of an applied electric field and forced light scattering technique. An optical index grating was written in the device in a holographic tilted configuration by overlapping two laser beams at 514 nm. Self diffraction of the writing beams and diffraction of a probe beam at 633 nm were measured. A high TBC gain coefficient of 270 cm-1 was achieved at a DC field applied of 3.4 V/μm. First-order diffraction efficiencies were evaluated with a maximum efficiency of 7% in the dynamic grating with a nonlinear refractive index, n2, 4 × 10-2 cm2/W for E0 = 3 V /μ m .