Abstract-Liquid-crystal-based magnetically tunable terahertz achromatic quarter-wave plate

Cho-Fan Hsieh, Chan-Shan Yang, Fang-Cih Shih, Ru-Pin Pan, and Ci-Ling Pan

Fig. 1 The LC-based achromatic wave plate has three elements, A, B and C. Each tunable retarder (TR) consists of a pair of rotatable permanent magnets and a homeotropically aligned LC cell. The FP and RA represent polarizer with fixed angle at −75° and rotating analyzer, respectively. Thicknesses of LC layers in TRA, TRB and TRCwere dA = 2.56 mm, dB = 3.86 mm, and dC = 2.56 mm, respectively.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-7-9933

Development of the wideband and tunable quasi-optic terahertz (THz) components is in high demand. In this work, we demonstrate a tunable achromatic quarter-wave plate (AQWP) for the THz frequency range. The phase retardation of this device can be set at 90° ± 9° from 0.20 to 0.50 THz. The operation range from 0.20 to 0.50 THz can be tuned to from 0.30 to 0.70 THz by introducing three nematic liquid crystals phase retarders, of which the birefringence can be magnetically tuned. The frequency-dependent phase retardation is in good agreement with theoretical predictions.

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