Terahertz dual-mechanism dual-band linear-to-circular polarization converter with one-octave band separation and orthogonal polarization

Multi-band polarization converters are crucial for reducing coupling between multiple-input multiple-output antenna components, promoting the integration of communication systems, and improving information transmission efficiency. However, current research faces challenges such as narrow operational bandwidth, low conversion efficiency, and lack of correlation between frequency bands for multi-band operation. A dual-wideband linear-to-circular (LC) polarization converter (PC) based on the dual mechanism of metal and dielectric is proposed in this paper. The unit cell of LC PC is optimized through three steps from a conventional metal-dielectric-metal structure. The optimization primarily involves creating cavities with special structures in the dielectric, which introduces the mechanism of dielectric resonance in addition to the original metal resonance. Simulation results demonstrate that this LC PC can convert incident linearly polarized waves into orthogonal circularly polarized waves in two nonadjacent frequency bands. The upper and lower cutoff frequencies of the second frequency band are exactly twice those of the first. The first operating frequency band ranges from 0.645 to 0.865 THz, with a relative bandwidth of 29%, producing a right-handed circularly polarized wave. The second operating frequency band is 1.29-1.73 THz, with a relative bandwidth of 29%, and the circularly polarized wave is left-handed. The device's capability to achieve LC polarization conversion with frequency-doubling relationship and orthogonal circular polarization makes it promising for applications in advanced high-speed communications, signal encryption, quantum information technology, and differential detection of chiral molecules.