Investigation of Photorefractive Effect in Dye Doped PDLC: TBC Experiments and Photoinduced Currents Measurements

Abstract

Results are reported on the wave mixing characterisation of dye-doped dispersion of liquid crystalline droplets in a polymer matrix (PDLC) by means two beam coupling experiments and experimental observation of photoinduced DC current, which arise in these materials under cw laser-beam illumination. We determine the TBC gain by means of the asymmetric energy transfer measurements and the amplitude and the phase shift of the phase grating and amplitude grating by means the TBC translation technique measurements. The experimental results of this first characterisation reveal the nonlocality of the effect: the gratings obtained are essentially the phase gratings spatially shifted of π/2 respect to the interference pattern. The photoinduced currents reveal transient behaviour, i.e. a relaxation to zero value after an initial increase. A qualitative discussion of the obtained results is reported. The observation and the results of the experiments evidence the photorefractive nature of the light-induced diffraction gratings, which were earlier observed in these materials.