TeraHertz wideband cross-polarization conversion metasurface based on double split-ring resonator

This paper presents the design and analysis of a switchable metasurface for wideband cross-polarization conversion in the terahertz (THz) regime. A dual-split ring resonator (DSRR) connected with a narrow metallic strip is used to achieve wideband cross-polar conversion from 2–4.85 THz. Till date, this is the highest reported bandwidth for a THz cross-polarization conversion metasurface. This wideband operation is achieved by exciting the closely spaced resonant frequencies of the DSRR occurring at 2.22 THz, 2.78 THz, 3.96 THz, and 4.68 THz. Additionally, photoconductive silicon is integrated in between the gaps of DSRR for continuous tuning in the operating frequency range. The proposed polarization converter has a compact unit cell size of 0.29 λ0, where λ0 is the free space wavelength at the lowest cut-off frequency. The proposed cross-polarizer achieved excellent polarization conversion ratio (PCR) of ≥ 94% over the entire bandwidth and exhibits wide angular stability up to 45∘. With these advantages, the proposed metasurface has potential applications in THz communication systems, especially in the field of imaging and sensing.