Twisted Nematic Liquid-Crystal-Based Terahertz Phase Shifter using Pristine PEDOT: PSS Transparent Conducting Electrodes

For this study, we demonstrated three different types of twisted nematic (TN) liquid crystal (LC) terahertz (THz) phase shifters using pristine poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) thin films as transparent conducting electrodes (TCEs). The transmittance of spin-coate...

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Bibliographic Details
Published in:Applied sciences 2019-02, Vol.9 (4), p.761
Main Authors: Sahoo, Anup, Yang, Chan-Shan, Yen, Chun-Ling, Lin, Hung-Chun, Wang, Yu-Jen, Lin, Yi-Hsin, Wada, Osamu, Pan, Ci-Ling
Format: Article
Language:English
Subjects:
Birefringence
Electrodes
Graphene
Investigations
liquid crystals
Military technology
Nematic crystals
Organic chemistry
PEDOT: PSS
phase shifter
Phase shifters
TCE
terahertz
Terahertz frequencies
Thickness
Thin films
THz
transparent conducting electrode
twisted nematic
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Summary:For this study, we demonstrated three different types of twisted nematic (TN) liquid crystal (LC) terahertz (THz) phase shifters using pristine poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) thin films as transparent conducting electrodes (TCEs). The transmittance of spin-coated pristine PEDOT: PSS thin film was as high as 92% in the frequency range of 0.2–1.2 THz. This is among the highest reported. Several TN-LC cells were constructed in a comparative study, which confirmed the reliability of pristine PEDOT: PSS as a TCE layer for THz phase shifter applications. The highest phase shift, required root-mean-square (RMS) driving voltage, and threshold voltage achieved by devices tested were 95.2° at 1 THz, 7.2 VRMS, and 0.5 VRMS, respectively. The thickness of the LC layer for the phase shifter was 250 µm, approximately half as thick as previous designs. In addition, the pristine PEDOT: PSS-based TN-LC phase shifter exhibited a figure-of-merit (FOM) value of approximately 6.65 degree·dB−1·V−1. This compared favorably with previously reported homogeneously aligned phase shifters with an FOM of 2.19 degree·dB−1·V−1. Our results indicated that a twisted nematic LC cell with pristine PEDOT: PSS thin films as electrodes is a good combination for a THz phase shifter and wave plates as well as other LC-based THz devices.
ISSN:2076-3417
2076-3417
DOI:10.3390/app9040761