Terahertz waveguide multiplexers: A review

Abstract Terahertz (THz) band, which owns abundant and underexplored frequency spectrum, has provided rich scientific and technological opportunities in numerous research fields, such as radio astronomy, atmospheric science and high‐speed communication. As one of the key components in THz systems, the multiplexer cannot only separate/combine different bands, but can also promote the development of THz instruments toward wider band and more multibands. Thanks to the high‐precision computer numerical control milling and micromachining technologies, a lot of THz waveguide multiplexers have been reported in recent years. According to the classification of design configurations, this article offers a brief overview on the developed THz multiplexers. In addition, the performance and system applications of different waveguide‐typed multiplexers are discussed. Therefore, this review will provide a valuable reference for the further development of THz waveguide multiplexers with high performance.