C-Shaped Single Split-Ring Resonator and Organic Electrochemical Transistor Optical Metasurfaces for Terahertz Beam Steering Applications

Abstract

Beam steering is a technique that controls the direction of a beam of radiation as it travels from transmitter to receiver, allowing for focused delivery of energy to certain target locations. In the case of wireless communication, this allows a transmitter to compensate for the path loss signal attenuation it encounters when emitting over the air. Terahertz (THz) and sub-THz radiation—electromagnetic emittance ranging from 10 GHz to 10 THz—is considered to be the next frontier of wireless communication given its ability to provide much higher data speeds and support a larger user capacity compared to current networks. Additionally, sub-THz has gained significant traction in imaging and biomedical applications given its small wavelengths—which provide high sensing resolution—and high sensitivity to relevant biomarkers. Furthermore, the development of reliable means of controlling THz radiation is necessary for the development of these THz communication, imaging, and biomedical diagnostic systems. In this paper, we present a metasurface fabricated with a 2D array of C-shaped single split-ring resonators (SRRs) that when linearly polarized radiation at sub-THz (60 GHz) frequency is incident on the C-shaped single split-ring resonator metasurface, the radiation will be steered at some predetermined angle according to the metasurface’s C-shaped single split-ring resonator architecture. We show that this beam steering can be turned off via thin films of a depletion mode organic semiconductor such as Poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and remains intact with thin films of accumulation mode organic semiconductors such as pG(2T-3T). Going forward we aim to apply these insights to make a reconfigurable metasurface whose beam steering properties can be turned on and off, likely by turning organic electrochemical transistors placed over the resonator gap openings and fabricated with PEDOT:PSS off and on respectively.