Optimization of the electrospun-aligned microfiber composite with liquid crystal for terahertz wave variable phase shifters

Abstract

In this study, electrospun microfibers (MFs) were produced and used as key materials to optimize the composite with liquid crystal (LC) for terahertz (THz) wave phase shifters. These MFs, with an average diameter of 1.4 μm, were produced using the polymer solution concentration of 14 wt% and spinning voltage of 13 kV. When MFs were combined with LC, the measured results of the electrical characteristics showed that 14 wt% MFs provided an outstanding solution to the problem of a significant reduction in the natural birefringence of pure LC. The birefringence in the THz frequency range of the composite using 14 wt% MFs approached 90% compared with that using pure LC. Additionally, the decay time drastically shortened from hundreds of seconds for pure LC to hundreds of milliseconds for MF/LC composite and was independent of device thickness.

Continuously reconfigurable 100 GHz band phased array antenna with improved response time using a microfiber/liquid crystal composite

“…MF sheets with a total thickness of 1 mm were employed to accelerate the response of the thick LC layer. As described in the previous report, 17) the introduction of MFs results in the thick LC layer separating into numerous thin layers, each measuring several micrometers. When the electric field is removed, the LC molecules experience anchoring forces from adjacent microfibers, causing them to move independently within these thin layers rather than across the entire thick LC layer.…”

“…We chose the non-radiative dielectric (NRD) waveguide structure for our phase shifter because of its high performance, as reported in previous work. 17) Consequently, a simple and low-loss transition from the rectangular waveguide to the NRD guide is required to implement an LC-based PAA. High-density polyethylene (HDPE, ε = 2.3) is employed as the dielectric material in the NRD structure because of its minimal loss in the HF range.…”

“…In this study, we used LC SL004 as a substitute for RDP-A3123 and RDP-94990 reported in previous studies. 17,23) These LCs are manufactured by DIC Corporation (Japan), and SL004 is a novel nematic LC specifically designed for THz frequencies. The measurement results presented in Figs.…”

“…Furthermore, the birefringence of MF/LC is reduced in comparison to that of pure LC. This can be explained by considering that the volume ratio of LC in the composite is approximately 90% 17) in contrast to 100% in its pure state. At 100 GHz, the birefringence of LC and MF/LC measures approximately 0.295 and 0.235 (representing 79.7% of the value of LC), respectively, demonstrating that MF/LC also exhibits substantial THz birefringence.…”

“…Previously, we reported response improvements in thick LC devices using aligned microfibers (MFs). The measured results demonstrate that MFs induce a slight decrease in dielectric anisotropy and THz birefringence, along with a minor variation in the rise time, while effectively reducing the decay time from several tens of minutes to a few hundred ms. 17) In this study, we aim to develop a cost-effective and compact 100 GHz band PAA using an MF/LC composite while maintaining high performance that meets all three aforementioned conditions.…”