Frequency-Tunable Absorber using Liquid Crystal at 140 GHz

Abstract

This paper presents a new class of frequency-tunable sub-terahertz absorber using liquid crystal (LC) exemplified at 140 GHz. More than 90% absorption of incident EM wave is obtained around the frequency of 140 GHz. The 90% absorption frequency band can be electronically tuned in-between 137 - 147 GHz by varying the applied biasing voltage across the LC in the range of peak-to-peak voltage 0 – 30 V. The absorption frequency band is stable with respect to oblique incidence in TE mode for incident angle variation in the range of ± 400. In TM mode, the leftward frequency shifting is observed for oblique incidence in the range of ± 800 while maintaining more than 90% absorption of the incident EM wave. This tunable absorber can be used to design multifunctional reconfigurable intelligent surface (RIS) with absorption and reflection reconfigurability for sub-terahertz wireless applications. This design features one of the widest tunable absorption bandwidth and incident angle range to be reported in literature. IEEE