Sketches of (a) the reference cell and (b) the LC cell. The substrates are fused silica and the alignment of LC cell is homogeneous.
Schematic of the terahertz-TDS. PBS: polarization beam splitter. and : terahertz polarizer and analyzer, respectively.
(a) Temporal profiles of the terahertz signals before (solid line) and after (dash line) purging. (b) The power spectra of the terahertz signals before (solid line) and after (dash line) purging. Several absorption lines of water vapor appear before purging. The relative humidities before and after purging are 53% and 3%, respectively.
Transmitted terahertz signals through the reference (solid line) and LC cells (dashed line) for (a) ray and (b) ray at . The noise, magnified by two hundred times, is also shown as the thin solid lines.
The optical constants of 5CB, and , are plotted as functions of frequency. The solid circles and the open circles are the extraordinary and ordinary indices at , respectively. The crosses are the values of optical constants of 5CB in the isotropic phase at . Error bars are indicated, unless they are smaller than the sizes of the symbols.
Extraordinary and ordinary refractive indices of 5CB are plotted as functions of reduced temperature at frequencies of 0.344, 0.500, 0.656, and 0.750 THz. The solid and the open circles represent and , respectively. The stars are data for the refractive index of 5CB in the isotropic phase. The solid lines are the average index, at temperatures below .
Birefringence of 5CB measured at 0.344, 0.500, 0.656, and 0.750 THz are plotted as a function of reduced temperature. The curves are the fitting results.
Extraordinary (solid triangles) and ordinary (open triangles) refractive indices for 5CB at reported in Ref. 19 are plotted together with the corresponding data (solid and open circles) measured as functions of frequency.
Extraordinary (solid circles) and ordinary (open circles) refractive indices of 5CB measured by the terahertz time-domain spectrometer, not purged with dry nitrogen. The terahertz beam passed through the cell is collimated and at normal incidence.
The fitting parameters of Eq. (5) for frequencies from 0.219 to 0.937 THz. (, , ) and (, , ) are for and , respectively.
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