Investigation of photorefractive effect in dye doped PDLC: TBC experimentsand photoinduced currents measurements

Results are reported on the wave mixing characterisation of dye-doped dispe rsion of liquid crystalline droplets in a polymer matrix (PDLC) by means tw o 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 measur ements and tile amplitude and The phase shift of the phase grating and ampl itude grating by means the TBC translation technique measurements. The expe rimental results of this first characterisation reveal the nonlocality of t ile effect: the gratings obtained are essentially the phase gratings spatia lly shifted of pi /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 re ported. The observation and the results of tile experiments evidence the ph otorefractive nature of the light-induced diffraction gratings, which were earlier observed in these materials.