Active meta polarizer for terahertz frequencies

Abstract

Active meta polarizers based on phase-change materials have recently led to emerging developments in terahertz devices and systems for imaging, security, and high-speed communications. Existing technologies of adaptive control of meta polarizers are limited to the complexity of external stimuli. Here, we introduce an active terahertz polarizer consisting of a single layer of large array patterns of vanadium dioxide material integrated with metallic patch matrix to dynamically reconfigure the polarization of the terahertz waves. The proposed active polarizer is simple in structure and can independently manipulate the polarization of the incident THz waves in two orthogonal directions. In addition, the device can also be performing as a highly efficient reflector at the same frequencies. We demonstrate that efficient and fast polarization changes of THz waves can be achieved over a wide operating bandwidth. Compared with other active polarizers using mechanical, optical and thermal controls, it can be conveniently manipulated with DC bias without any external actuators, intense laser source or heater. Therefore, with the advantages of high efficiency, compact size, low loss, low cost and fast response, the proposed polarizer can be highly integrative and practical to operate within adaptive terahertz circuits and systems.

Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links

“…Since the emergence of multiple-input, multiple-output (MIMO) technology for wireless communication, polarization modulation (PoM) has gained more and more attention thanks to its excellent signal distinguishability, thereby increasing spectrum efficiency [134,135]. Metasurfaces with active elements for polarization modulation at THz frequencies were investigated in [136][137][138][139] and were found to have great potential to be utilized for future 6G wireless communications. Another promising area for future THz RIS applications is space-time-coding digital metasurfaces with have multifrequency control for beam shaping and steering [140].…”

Terahertz Devices Using the Optical Activation of GeTe Phase Change Materials: Toward Fully Reconfigurable Functionalities

“…The strong contrast in THz amplitude signals transmitted through the GeTe films optically prepared in the two different states suggests that simple structures made only in GeTe (without additional metallic structures) could be feasible, offering interesting and promising opportunities for developing active THz reconfigurable devices. In particular, THz polarizers are essential devices with critical roles in imaging and wireless communication applications. − For demonstrating the potential capabilities of the GeTe material for these applications, we develop what we believe being the first all-PCM THz polarizer, that is, the first device using the metallic/crystalline state of GeTe to produce the selection of the polarization state of a transmitted THz wave.…”

Compact Terahertz Dielectric Folded Metasurface

“…As introduced in the above Folded Metasurface section, the top metasurface should be reflective and transparent for u-and v-polarization incidences, respectively. So far, most linear polarizers are based on metallic grating patterned on a substrate, [47][48][49][51][52][53] resulting in inherent conduction loss. Figure 3a shows the configuration of the employed top metasurface, which consists of two identical Si grating layers with a separation of s. The metasurface is assumed infinite in the u-direction and infinitely periodic along the v-direction.…”