Dynamic holography with pulse ps laser in hybrid polymer liquid crystal panel

Abstract

We report on the photorefractive properties of hybrid: polymer - nematic liquid crystal panels (HPLCP) equipped with either one or two photoconducting polymeric layers. In the present work we focused our attention on studies of PVK:TNF (poly N-vinyl carbazole doped with trinitrofluorenone) hybrid polymer liquid crystal (E7 - Merck) panels under short pulse laser illumination conditions. The diffraction gratings in a LC panel were induced by crossed beams generated by doubled in frequency Nd:YAG laser (?= 532 nm) delivering pulses of 20 ps duration. So induced gratings were read by a cw laser radiation coming from a weak power He-Ne laser working at ? = 632.8 nm. The light detector was set at the angle of the first order diffracted beam of He-Ne laser. The temporal evolution of intensity of first order diffraction was measured in PVK:TNF hybrid liquid crystal panels for various experimental conditions, like driving voltage, beam geometry, gratings spacing and others. The substantial diffraction was observed already for times lower than 1 ms after the pulse and the grating decay was completed within hundreds of milliseconds.