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High-Transmittance 2π Electrically Tunable Terahertz Phase Shifter with CMOS-Compatible Driving Voltage Enabled by Liquid Crystals

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Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei 11677, Taiwan
2
Undergraduate Program of Electro-Optical Engineering, National Taiwan Normal University, Taipei 11677, Taiwan
3
Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
4
Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
5
Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2019, 9(2), 271; https://doi.org/10.3390/app9020271
Received: 13 November 2018 / Revised: 23 December 2018 / Accepted: 8 January 2019 / Published: 14 January 2019
(This article belongs to the Special Issue Liquid Crystal THz Photonics: Materials, Devices and Applications)
We have investigated tunable terahertz (THz) phase shifters that are based on a sandwiched liquid crystal (LC) cell with indium–tin–oxide (ITO) nanowhiskers (NWhs) as transparent electrodes. More than 360° of phase shift at 1.0 THz was achieved at a driving voltage as low as ~2.6 V (rms). This is approximately 40 times smaller than that reported in previous works using an electrically tuned LC device. Significance of the NWhs in reducing the required voltage is demonstrated. Overall transmittance of the device is as high as 30%, which is accountable by absorption losses of ITO NWhs, quartz substrate and LC. Experimental results are in good agreement with a theoretical formulism while taking into account super-thick LC cells (~1 mm) and pretilt angles. We also propose and demonstrate a novel THz technique for measuring pretilt angles of liquid crystals. View Full-Text
Keywords: far infrared; nanomaterials; terahertz; transparent conductive coatings; phase shift; liquid crystals; birefringence; antireflection coatings far infrared; nanomaterials; terahertz; transparent conductive coatings; phase shift; liquid crystals; birefringence; antireflection coatings
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Yang, C.-S.; Kuo, C.; Chen, P.-H.; Wu, W.-T.; Pan, R.-P.; Yu, P.; Pan, C.-L. High-Transmittance 2π Electrically Tunable Terahertz Phase Shifter with CMOS-Compatible Driving Voltage Enabled by Liquid Crystals. Appl. Sci. 2019, 9, 271.

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