Terahertz waves and liquid crystals: prospects and challenges

Vieweg, N.; Deninger, A.

doi:10.1117/12.2013315

Cited by 10 publications

(7 citation statements)

References 99 publications

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“…1,2 LCs should have high birefringence to limit the necessary thickness of the devices as well as chemical stability for their reliable operation. [3][4][5][6][7] E7 is a well known, stable LC which has a relatively high birefringence in the THz range (∆n E7 = 0.13). 8 New LCs, specifically designed for THz have also been synthesised and the details of their chemical formulae reported.…”

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confidence: 99%

Refractive indices and birefringence of hybrid liquid crystal - nanoparticles composite materials in the terahertz region

et al. 2015

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We show that a hybrid LC-ferroelectric nanoparticle suspension of liquid crystal E7 doped with BaTiO3 nanoparticles leads to 10% increase in birefringence in the THz region of spectrum as compared to pure E7. Doped liquid crystals can be used to increase performance of THz modulators and waveplates. BaTiO3 nanoparticles used in the mixture were synthesised with the sol gel technique, and their refractive index has been measured in THz in powder form and in solution.

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confidence: 99%

Refractive indices and birefringence of hybrid liquid crystal - nanoparticles composite materials in the terahertz region

et al. 2015

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“…It should be noted that the far-IR spectra of Vectra A950 were measured for the first time. To date only far-IR spectra of low molecular LC have been studied in detail, but they are sufficiently scattered and primarily related to low-molecular nematics type of MBBA (4-methoxy-4-benzylideneaniline) with benzene rings as a mesogens and alkyl groups as a flexible spacers [14,15].…”

Section: Resultsmentioning

confidence: 99%

Peculiarities of The Orientational State of Liquid-Crystal Completely Aromatic Thermotropic Copolymer

Ryzhov¹

2017

J. Res. Updates Polym. Sci.

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Polarization far-IR spectroscopy has been used to carry out a comparative study of the spectra of granules and fibers of completely aromatic thermotropic liquid-crystal copolymer Vectra A950. The analysis of terahertz polarization IR spectra Vectra A950 showed that in contrast to the mid-IR, dichroic ratio of the absorption bands in the spectra of fibers and granules, substantially different. It is shown that the difference between the value and the orientation order parameter in the samples is determined by and correlated with the intensity of the local dynamics of polymer chains, such as the librational mobility of phenylene and naphthalene rings of the copolymer mesogens. The results suggest the possibility carrying out an independent evaluation of the spectroscopic parameters reflecting the properties of intermolecular interactions in oriented the liquid-crystalline polymers for their low-frequency spectra.

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“…The orientational order of the LCP molecules gives rise to anisotropic properties: The 1 E540i is a trademark of TICONA. extraordinary refractive index is higher than the ordinary refractive index [38,39] and consequently, the pulse undergoes a larger time shift in the case of extraordinary polarization. Note that the pulse amplitudes are nearly identical for both polarizations, indicating similar absorption coefficients.…”

Section: Terahertz Spectroscopymentioning

confidence: 99%

Terahertz-time domain spectrometer with 90 dB peak dynamic range

Vieweg

Rettich

Deninger

et al. 2014

J Infrared Milli Terahz Waves

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179

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Many time-domain terahertz applications require systems with high bandwidth, high signal-to-noise ratio and fast measurement speed. In this paper we present a terahertz time-domain spectrometer based on 1550 nm fiber laser technology and InGaAs photoconductive switches. The delay stage offers both a high scanning speed of up to 60 traces / s and a flexible adjustment of the measurement range from 15 ps -200 ps. Owing to a precise reconstruction of the time axis, the system achieves a high dynamic range: a single pulse trace of 50 ps is acquired in only 44 ms, and transformed into a spectrum with a peak dynamic range of 60 dB. With 1000 averages, the dynamic range increases to 90 dB and the measurement time still remains well below one minute. We demonstrate the suitability of the system for spectroscopic measurements and terahertz imaging.

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Terahertz waves and liquid crystals: prospects and challenges

Cited by 10 publications

References 99 publications

Refractive indices and birefringence of hybrid liquid crystal - nanoparticles composite materials in the terahertz region

Refractive indices and birefringence of hybrid liquid crystal - nanoparticles composite materials in the terahertz region

Peculiarities of The Orientational State of Liquid-Crystal Completely Aromatic Thermotropic Copolymer

Terahertz-time domain spectrometer with 90 dB peak dynamic range

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