Experimental measurements of the spatial correlation lengths of the director axis fluctuations of nematic liquid crystals

Experimental study of the director axis fluctuations in nematic liquid crystals shows that director axis spatial fluctuations can be assimilated to a spatially correlated noise with lengths of order micron. These fluctuations are imaged using orthoscopic polarised light microscopy from which spatial autocorrelation functions are calculated to get the characteristic spatial correlation lengths. The probability density function of director axis fluctuations demonstrates that the distribution is of normal type. A method to numerically generate the correlated noise, with the right experimental features, needed for numerical simulations is given. It is based on the knowledge of the experimental amplitude spectral density function.