Terahertz Off-Axis Focus Polarization Converter Based on Metasurface

Abstract

In order to satisfy the requirements of terahertz time-domain spectrum system under specific circumstances, an off-axis focus reflective polarization converter in terahertz band is proposed. By combining the principle of phase compensation and phase gradient metasurface, a reflective array containing 20 × 20 units is designed. The phase distribution along the metasurface is calculated through the principle of optical path reversibility. Geometric rotation and resonant frequency modulation constitute the phase change of the unit that can overlap one another without interference. Compared with the conventional reflective polarization converter in terahertz band, the proposed one could reflect the normally incident terahertz wave while providing larger energy at the focus. The simulation results show that the proposed polarization converter has good performance in both polarization conversion and electromagnetic focus, which has significant practical application in numerous situations.

Wideband and Tunable Reflective Cross-Polarization Conversion Metasurface for TeraHertz Applications

“…Metasurfaces employing sub-wavelength resonant structures are widely being used for polarization control purposes. In the literature, metasurface polarization converters have been designed based on transmissive mode [10], [11], [12], [13], [14], transmissive and reflective mode [15] and reflective modes [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28]. The transmissive type polarization converters suffer due to narrow bandwidth [13], [14] or require multilayer topologies to provide wideband operation [11].…”

“…However, because of the highly resonant characteristics of the split-ring, the polarization conversion ratio (PCR) is limited to only 80% in these works. In [19], [20], an array of H-shaped unit cell structures are introduced for reflecting phases, resulting in cross-polarization conversion bandwidth of 0.2 THz and 0.3 THz, respectively. The PCR of these reported works are ≥ 85%.…”