Non-radiative dielectric (NRD) waveguides are known as a type of transmission line with advantages such as the restriction of undesired radiation at curved sections and discontinuities. A new type of terahertz phase shifter which uses liquid crystal as the dielectric material in an NRD waveguide is presented for the first time. The phase change is very large but the decay time is extremely long. By inserting a PET sheet into a nematic liquid crystal-loaded NRD waveguide, the thickness of the liquid crystal layer is reduced. Although the phase change decreases, the decay time is greatly improved, and the availability of the partial use of nematic liquid crystal in the dielectric material of an NRD waveguide is confirmed. By comparing dielectric response results of the ordinary sandwiched cells with the experimental results of nematic liquid crystal-loaded NRD waveguides, it is confirmed that the response time does not depend on the kind of device.

Liquid crystals, which have high dielectric anisotropy even in the terahertz region and are easily controllable for dielectric permittivity by applying an electric field, have become increasingly attractive in recent years. The non-radiative dielectric (NRD) waveguide has a structure in which a dielectric line is sandwiched between two metal plates and by replacing the dielectric part with liquid crystal, a low loss liquid crystal-loaded NRD waveguide type terahertz phase shifter can be obtained. However, since the thickness of the liquid crystal layer is several hundred micrometers, it has a response time of as long as several hundred seconds when the driving voltage is removed. It is necessary to devise improvements for practical application. By inserting two polyethylene terephthalate (PET) films and reducing the thickness of the liquid crystal layer, the decay time was improved well, but the phase change was significantly reduced. In this study, we report improving both decay time and phase change with aligned nanofiber/liquid crystal complex. In addition, we demonstrate liquid crystal-load phase shifter, which has 360° phase change and the response time below one second.

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SUMMARY With nowadays development of cellular phones and satellite communications, liquid crystal materials have attracted considerable attention for realizing these electrically controllable microwave and milliwave components. As usual, nematic liquid crystal is mainly used for microstrip line (MSL) phase shifter, but when driving voltage is removed, the response time is very long. In this study, we discuss application of polymer stabilized nematic liquid crystals with UV polymerization for improving the response time in MSL phase shifter in which phase shift is about two times larger than that in CPW phase shifter.