Harnessing all-dielectric metamaterials to precisely manipulate the polarization state of light

Polarization is one of the fundamental characteristics of electromagnetic waves. It can convey valuable vector information in sensitive measurements and signal transmission, which is promising in various fields such as environmental monitoring, biomedical sciences, and marine exploration. Particularly in the terahertz frequency range, traditional device design methods and structures can only achieve limited performance. Designing efficient modulator devices for high-bandwidth terahertz waves presents a significant challenge.

Researchers led by Prof. Liang Wu at Tianjin University (TJU), China, have been conducted in the field of all-dielectric metamaterials, specifically focusing on utilizing these materials and their structural design to achieve effective broadband polarization conversion in the terahertz frequency range. Here, they propose a cross-shaped microstructure metamaterial for achieving cross-polarization conversion and linear-to-circular polarization conversion in the terahertz frequency range. Within a wide frequency range of 1.00 to 2.32 THz, the average conversion efficiency of cross-linear waves exceeds 80%, with the highest conversion efficiency peak reaching an impressive 99.97%. Additionally, the employed structure facilitates the conversion from linear to circular polarization, with an ellipticity of 1 at 0.85 THz. This work by the researchers also provides valuable insights for the design of other metamaterials capable of broadband, high-efficiency, and multi-polarization mode manipulation. The work entitled “An all-silicon design of a high-efficiency broadband transmissive terahertz polarization convertor” was published on Frontiers of Optoelectronics (published on Dec. 6, 2023).