Benjamin S.-Y. Ung, Xudong Liu, Edward P. J. Parrott, Abhishek Kumar Srivastava, Hongkyu Park, Vladimir G. Chigrinov, Emma Pickwell-MacPherson
http://ieeexplore.ieee.org/document/8283624/
Terahertz (THz) phase shifters are an essential component needed to realize many potential applications. Liquid crystals (LC) are commonly used at optical frequencies, yet to achieve an equivalent phase shift at THz frequencies the LC layer needs to be orders of magnitude thicker. Consequently, the time for the LC to relax back to its initial state is prohibitively slow. In this paper, we show for the first time how a thick, nematic phase LC cell can be switched actively in both directions, thereby achieving fast phase shifting of THz light. We call this THz in-plane and THz out-plane (TIP-TOP) switching. To achieve this, we have designed and fabricated a novel electrode structure, able to switch to and from both in- and out-plane orientations (TIP-TOP). The performance of the fabricated device provides an actively controllable phase delay with an ON–OFF cycle switching time of approximately 0.5 s: almost 100 times faster than the usual cycle time which exceeds 40 s. Furthermore, the analysis of the director distributions allows us to understand the causes of the asymmetric switching times. The TIP-TOP cell presents the capability to work as a low insertion loss, fast THz phase shifter and could be scaled up to realize a phased array device.
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