High Birefringence Liquid Crystals

Dąbrowski, R.; Kula, Przemysław; Herman, Jakub

doi:10.3390/cryst3030443

Cited by 235 publications

(113 citation statements)

References 125 publications

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“…These materials have a positive anisotropy with n e > n o and dichroism α e < α o for CN mixtures in the all investigated THz range, while α e > α o for mixtures comprising isothiocyanato compounds above 1.0 THz range. It has been stated [31] that there are several factors influencing the birefringence: terminal groups, ring structures and bridge groups. From the available LC constituent data we have, molecular mixtures with more benzene rings, NCS terminal and triple bridge bond exhibit larger birefringence compared to those in the normal CB family.…”

Section: Discussionmentioning

confidence: 99%

High-birefringence nematic liquid crystal for broadband THz applications

Tan

Pivnenko

et al. 2016

Liquid Crystals

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Liquid crystals (LCs) have been studied extensively in the visible range for their dielectric tunability, and the characterisation in the terahertz (THz) range has gained increasing interest due to the need for active THz modulation and switching devices. In this paper, we use THz timedomain spectroscopy to measure the frequency-dependent birefringence and the absorption coefficient of a number of commercial and non-commercial nematic LCs, including E7, BL037, MDA-98-1602, LCMS-107, GT3-23001 and 1825, over a range of bias voltages at room temperature. Furthermore, several basic components of LC mixture are analysed to establish their contributions to birefringence and theoretical model is used to fit the absorption spectra. The large tunability and low loss measured for a range of samples show that the LCs are useful tunable dielectrics for compact, efficient and broadband THz devices. ARTICLE HISTORY

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Section: Discussionmentioning

confidence: 99%

High-birefringence nematic liquid crystal for broadband THz applications

Tan

Pivnenko

et al. 2016

Liquid Crystals

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“…Again, the device operates as a fast switchable barrier filter, and a green to dark switching is observed. Although the anisotropy of the birefringence of the used NLC is rather small (Δn = 0.11) compared to high birefringence NLC (Δn up to 0.7) [33,34], the resulting operation range of about 30 nm is already large enough for the demonstrated barrier filter function.…”

Section: Evaluation Of Novel Fast Tunable Interference Color Filtermentioning

confidence: 99%

Time-Sequential Working Wavelength-Selective Filter for Flat Autostereoscopic Displays

et al. 2017

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A time-sequential working, spatially-multiplexed autostereoscopic 3D display design consisting of a fast switchable RGB-color filter array and a fast color display is presented. The newly-introduced 3D display design is usable as a multi-user display, as well as a single-user system. The wavelength-selective filter barrier emits the light from a larger aperture than common autostereoscopic barrier displays with similar barrier pitch and ascent. Measurements on a demonstrator with commercial display components, simulations and computational evaluations have been carried out to describe the proposed wavelength-selective display design in static states and to show the weak spots of display filters in commercial displays. An optical modelling of wavelength-selective barriers has been used for instance to calculate the light ray distribution properties of that arrangement. In the time-sequential implementation, it is important to avoid that quick eye or eyelid movement leads to visible color artifacts. Therefore, color filter cells, switching faster than conventional LC display cells, must distribute directed light from different primaries at the same time, to create a 3D presentation. For that, electric tunable liquid crystal Fabry-Pérot color filters are presented. They switch on-off the colors red, green and blue in the millisecond regime. Their active areas consist of a sub-micrometer-thick nematic layer sandwiched between dielectric mirrors and indium tin oxide (ITO)-electrodes. These cells shall switch narrowband light of red, green or blue. A barrier filter array for a high resolution, glasses-free 3D display has to be equipped with several thousand switchable filter elements having different color apertures.Keywords: fast switchable wavelength-selective elements; autostereoscopic image splitter; color filter barrier array; computational display; Fabry-Pérot color filter; on-off filter mode

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“…High birefringence reduces the liquid crystal cell gap and efficiently leads to a faster response time [1][2][3]8]. Liquid crystalline compounds such as fluoro-substituted biphenyl, terphenyl, tolane and phenyl tolane isothiocyanates are very useful for device applications because of their high optical birefringence [9]. The optical birefringence of a liquid crystal is mainly determined by the shape and size of the liquid crystal molecule, conjugation length, packing density and temperature [1,[10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Nematic liquid crystals exhibiting high birefringence

Thingujam

Bhattacharjee

Choudhury

et al. 2016

Opt Rev

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Two fluorinated isothiocyanato nematic liquid crystalline compounds, 4 0 -butylcyclohexyl-3, 5-difluoro-4-isothiocyanatobiphenyl and 4 0 -pentylcyclohexyl-3, 5-difluoro-4-isothiocynatobiphenyl are studied in detail to obtain their different physical parameters. Optical polarizing microscopy, differential scanning calorimetry, density and dielectric studies have been carried out for the two samples. Both the samples were found to have high clearing temperature ([100°C) and exhibit small enthalpy of transition. The two samples exhibit high optical birefringence (Dn [ 0.2). The values of order parameters for the two samples were obtained using different approaches, namely, Vuks', Neugebauer's, modified Vuks' and direct extrapolation method from birefringence data. Experimentally obtained values of order parameters have also been compared with theoretical Maier-Saupe values. The parallel and perpendicular components of dielectric permittivity values of the two compounds were also calculated and their anisotropy values were found to be small. The effect of temperature on the molecular dipole moment l and the angle of inclination b of the dipole axis with the director have also been investigated in this work.

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High Birefringence Liquid Crystals

Cited by 235 publications

References 125 publications

High-birefringence nematic liquid crystal for broadband THz applications

High-birefringence nematic liquid crystal for broadband THz applications

Time-Sequential Working Wavelength-Selective Filter for Flat Autostereoscopic Displays

Nematic liquid crystals exhibiting high birefringence

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