Active Terahertz Vortices With Broadband Near‐Far Field Multiplexing Based on Nonvolatile Plasmonic Metasurfaces

Terahertz (THz) vortices field carrying orbital angular momentum play a vital role in high‐capacity wireless communication. However, most existing devices remain a challenge in multi‐channel multiplexing, broadband operating frequency, and active capability. Here, a rotatable broadband THz vortex generator with near‐far field multiplexing is demonstrated based on a magneto‐optical (MO) plasmonic metasurface. The slit antennas on the metasurface are tailored to a series of ring arrays, which generate the first order surface plasmonic vortices for near field and second order free‐space vortices for far field, with a maximum mode purity of up to 98%. Utilizing the spectral fusion mechanism, the two sets of orthogonal slit antenna pairs with different peak excitation frequencies are selected as the coherent sources to construct the interference superposition field, enabling a broad operating band across the 0.4–0.72 THz range. Furthermore, by the Faraday rotation and magnetic storage effects of the MO layer of the metasurface, both the near and far vortex fields can be rotated with both nonvolatility and nonreciprocity. This active, broadband, multi‐channel MO plasmonic field control mechanism and its metadevice hold potential applications for THz communication and information processing