New method for analysis of electrooptical response in liquid crystal devices with non-monotonous relaxation

Abstract

ABSTRACT In the design and development of liquid crystal (LC) devices, it is crucial to determine the characteristic times of optical responses in devices driven with applied electric fields. These characteristic times associated with relaxation processes of the LC upon application (on) or removal (off) of an electric field are commonly calculated through measurement of the interval between 10% and 90% of the total change. Signals with non-monotonic oscillatory patterns originating either from the influence of backflow processes or from the variation in the phase shift between the anisotropic refractive indices in the reorientation dynamics complicate such a determination of the response times of LC devices. To obtain response times in LC devices with non-monotonous relaxation processes, we developed a novel numeric method that suppresses the oscillatory component of the signal and allows a direct determination of the characteristic times. The technique was validated with simulations of smooth and noisy data sets and was also applied to experimental data obtained from LC devices based on the LC 4-n-pentyl-4ʹ-cyanobiphenyl (5CB). The obtained results confirm that the method is reliable and applicable to data sets with complicated oscillatory patterns.