Design of All‐Metal 3D Anisotropic Metamaterial for Ultrabroadband Terahertz Reflective Linear Polarization Conversion

Abstract

Herein, a novel and simple design of all‐metal 3D anisotropic metamaterial (3DAMM) is proposed and investigated numerically, which can achieve a high‐efficient and wide‐angle ultrabroadband reflective linear–linear and dual‐band linear–circular polarization conversion in the terahertz (THz) region. The 3DAMM is composed of a periodic array of copper stand‐up split ring resonator (SRR) adhered on a copper film ground plane. Incident ultrabroadband linear polarization waves can be converted to its orthogonal counterpart after reflection due to the three neighboring plasmon resonances of the 3DAMM structure. The proposed design demonstrates a high conversion efficiency of over 90% within a relative bandwidth of 88.7% in the range of 0.62–1.61 THz, and its efficiency is validated for both transverse electric and transverse magnetic modes and a wide range of incident angles (0°–50°). This ultrabroadband and high‐efficient linear polarization conversion of the 3DAMM is attributed to multiple plasmon resonances within the operating frequency range. The surface current distributions on the unit cell show that the ultra‐broadband conversion behaviors result from the decomposed electric field components coupling with different resonance modes. Further simulation results suggest that the polarization conversion properties of the 3DAMM can be adjusted by changing the geometric parameters of the unit cell. The proposed 3DAMM‐based reflective linear polarization convertor can find potential applications in remote sensors, imaging systems, and reflector antennas at THz frequencies.