Multifrequency Driven Nematics

Abstract

Liquid crystals act on the amplitude and the phase of a wave front under applied electric fields. Ordinary LCs are known as field induced birefringence, thus both phase and amplitude modulation strongly depend on the voltage controllable molecular tilt. In this work we present electrooptical properties of novel liquid crystal (LC) mixture with frequency tunable capabilities from 100Hz to 10 KHz at constant applied voltage. The frequency tunability of presented mixtures shown here came from composition of three different families of rodlike liquid crystals. Dielectric measurements are reported for the compounds constituting frequency-controlled birefringence liquid crystal. Characterization protocols allowing the optimum classification of different components of this mixture, paying attention to all relevant parameters such as anisotropic polarizability, dielectric anisotropy, and dipole moment are presented.

Electro-Optical and Photo Stabilization Study of Nematic Ternary Mixture

“…As result of this combination, the LC mixture is a positive nematic with ∆ ε = 6.3 at 100 Hz, birefringence ∆ n = 0.32, and clearing temperature at about 120 °C. In fact, the results reported in [ 14 , 24 ] show that at room temperature, the electro-optical properties of this mixture are frequency tunable at kHz range. To measure the dielectric permittivity, the 5005 mixture has been injected in cells with gold electrodes and 0.7 mm thickness.…”

“…This limitation prevents dual-frequency nematic liquid crystals from finding commercial application. We would like to emphasize here that the multi-frequency LC studied in this work is different to conventional DFLCs; in fact, the dielectric anisotropy goes to zero instead of being negative at high frequencies [ 24 ]. The multi-frequency-controlled LC mixture presented in this work is a ternary mixture based on three LC components, two of which are dielectrically positive and one that is dielectrically neutral.…”

“…This mixture (named 5005) was formulated in the Institute of Chemistry at Military University of Technology in Warsaw, and it can be controlled similarly to DFLC, but its frequencies are low, and the sign of dielectric anisotropy does not change. Furthermore, using this mixture, multiple levels of phase modulation, tunable by adjusting the frequency of the applied signal from 3–34 kHz range, can be obtained [ 24 ]. This has a positive effect on the switch-ON time, which is strongly dependent on the applied voltage, when the amplitude modulation is applied.…”

Electro-Optical Switching of Dual-Frequency Nematic Liquid Crystals: Regimes of Thin and Thick Cells

“…This makes dual-frequency nematic liquid crystals (DFNLC) suitable materials for applications that require high phase shift and fast switching times. Although DFNLC are recognized as good candidates for the development of fast switching liquid crystal devices [18][19][20][21][22], their electro-optical performance over a broad range of liquid crystal layer thicknesses has not been studied. Typically, only a single value of the cell thickness has been considered.…”

Liquid Crystal Optical Devices

“…The second highlight is an article entitled "Multifrequency Driven Nematics," by Noureddine Bennis et al [8], fellow researchers from the Military University of Technology, Warsaw, Poland. This article addresses a novel LC mixture with frequency tunable capabilities.…”