Linear optical parameters of a dyed nematic mixture in the presence of an ac voltage

The tilt angle distribution of a nematic liquid crystal mixture doped with two anthraquinone derivatives having different molecular shapes was measured as a function of an external ac applied voltage. The voltage dependence of the birefringences, absorbances and linear absorption coefficients of the samples were predicted from the tilt angle distribution and were also determined experimentally. It was found a good agreement between predicted and experimental results, taking into account the absorption coefficients of the dyes. Moreover, the order parameter and the linear absorption coefficients of the dyes were determined in the nematic host. We find a marked difference in the order parameters and linear absorption coefficients of the guest–host combinations, with different dye molecular shapes.