Optical Constants of Two Typical Liquid Crystals 5CB and PCH5 in the THz Frequency Range.
The complex refractive indices of two benchmark nematic liquid crystal,4-4 '-n-pentyl-cyanobiphenyl (5CB) and 4-(trans-4'pentylcyclohexyl)-benzonitrile (PCH5) have been determinedin the frequency range from 0.2 to 0.8 THz. The technique of coherent THztime-domain spectroscopy (THz-TDS) was used. We show that the birefringenceof 5CB is in the range of 0.15 to 0.21, while that of PCH is from 0.01 to0.08. Both liquid crystals exhibit relatively small absorption in thisfrequency range. The large birefringence of 5CB indicates possible applications of liquid-crystal-based devices for modulation and polarizationcontrol of electromagnetic radiation in the THz frequency range.
Department of Electrophysics and the Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan 30010, R.O.C.
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Pan
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Tsai
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Chen
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Pan
5CB; PCH5; THz; absorption; birefringence; liquid crystal; optical constants; refractive index; time-domain spectroscopy