Optical nonlinearities induced by electric fields in nematic liquid crystals

Nonlinear phenomena induced by an electric field inside a nematic liquid crystal were studied. A planar oriented cell filled with 5CB nematic liquid crystal was subjected to an external voltage, higher than the threshold value for the Freedericksz transition, and a laser beam was sent perpendicular to the cell. Circular fringes appeared on the screen. The maximum number of diffraction fringes for different voltage values was measured and the experimental plot were in good agreement with theory. We performed a set of dynamic measurements of the fringes evolution from the moment when the laser beam was applied until the maximum number of fringes was reached, for each voltage, and the results were consistent with theoretical pattern.