Dynamical studies of gratings formed in polymer-dispersed liquid crystal films doped with a guest-host dye

This study investigated die dynamic behavior of the first-order diffraction efficiency of gratings formed in polymer-dispersed liquid crystal (PDLC) f ilms doped with a guest-host dye. PDLC films were fabricated using various LC-polymer mixing ratios, and written with various powers. Experimental res ults indicated that several peaks appeared in the curve of the first-order diffraction efficiency versus time. According to the light scattering study , we believe that the first peak was due to the superposition of density an d absorption gratings. The density grating was associated with the spatiall y varied molecular weight of polymer molecules across the sample. and the a bsorption grating resulted from the spatially varied density of free electr ons. The other peaks were caused by the superposition of the absorption and phase gratings. The phase grating was generated by the formation of a peri odic structure of polymer-rich and LC-rich regions in the sample. This stud y also proposes a model to explain these experimental results. Moreover, th e theory derived from this model correlates well with the experimental resu lts, allowing us to determine the amplitude of the final grating.