The complex refractive indices of the liquid crystal mixture E7 in the terahertz frequency range

College

College of Science

Department/Unit

Physics

Document Type

Article

Source Title

Journal of the Optical Society of America B

Volume

27

Issue

9

First Page

1866

Last Page

1873

Publication Date

9-2010

Abstract

We have used terahertz (THz) time-domain spectroscopy to investigate the complex optical constants and birefringence of a widely used liquid crystal mixture E7 in both nematic and isotropic phases (26ºC~70ºC). The extinction coefficient of E7 at room temperature is less than 0.035 and without sharp absorption features in the frequency range of 0.2~2.0 THz. The extraordinary (ne) and ordinary (no) indices of refraction at 26ºC are 1.690~1.704 and 1.557~1.581, respectively, giving rise to a birefringence of 0.130~0.148 in this frequency range. The temperature-dependent (26ºC~70ºC) order parameter extracted from the birefringence data agrees with that in the visible region quite well. Further, the temperature gradients of the THz optical constants of E7 are also determined. The optical constants of E7 in the THz or sub-millimeter wave range are found to deviate significantly from values predicated by the usual extended Cauchy equations used in the visible and near-infrared.

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Digitial Object Identifier (DOI)

10.1364/JOSAB.27.001866

Disciplines

Materials Science and Engineering

Keywords

Liquid crystals; Refractive index; Terahertz technology; Frequency spectra

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