Ferroelectric nematic liquid crystals have been extensively researched since their discovery in 2017 due to their intriguing optical and mechano-electrical properties. What sets the ferroelectric nematic phase apart from the ordinary nematic phase is its macroscopic polarization. By coupling the polarization field with an external electric field, we can modulate the orientation of the director field. In this Master's thesis, we investigate the dynamic response to an external electric field in two materials exhibiting a ferroelectric nematic phase: DIO and RM734. We examine the electro-optic response in commercial liquid crystal cells with various anchoring geometries using polarized optical microscopy. We demonstrate, that applying a voltage pulse induces a deformation at the electrode edges. This deformation extends into the cell interior. We determine characteristic switch-on and -off times by fitting a model to our measurements. By measuring the intensity of the transmitted light, we observe that at sufficiently high amplitudes of the external electric field, the equilibrium configuration of the director field changes. Next, we simulate the dynamic response using the Frank elastic theory and Jones calculus. We show that a more complex description of the system is needed to explain the experimental results fully. Finally, we obtain additional information about the dynamics using second harmonic generation microscopy.
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