Photo-induced electrohydrodynamical instabilities in anthraquinone-dye-doped nematics above Freedericksz threshold

Induced by nanosecond pulses of second harmonic generation from Nd:YAG laser the hydrodynamical instabilities in planar- and twist-oriented layers of the nematic 6CHBT doped with anthraquinone dyes under dc electric field in the region above the Freedericksz threshold were revealed. The dependence of diffraction efficiency on voltage is characterized by the two maxima which are corresponding to the two types of EHD-instabilities that have two characteristic decay times, one of them is of the order of 100 ms and second one is equal to several milliseconds.