Dual Non-Diffractive Beam Generation via Spin-and-Frequency Multiplexed All-Dielectric Metasurfaces.

Metasurfaces offer remarkable capabilities for manipulating electromagnetic waves and by incorporating multiplexing techniques can significantly increase the versatility of design possibilities. Here, we designed and experimentally demonstrated a series of dual non-diffractive beam generators for terahertz radiation based on all-dielectric metasurfaces. These generators could produce switchable Bessel beams and abruptly autofocusing beams depending on the spin and frequency of the incident terahertz waves. In addition, by further applying appropriate phase gradients in the design, these non-diffractive beams could be deflected in specified directions. It is also possible to simultaneously generate multiple non-diffractive beams with different properties. The generated non-diffractive beams were measured with near-field scanning terahertz microscopy, and the results agreed well with simulations. We believe that these metasurface-based beam generators hold tremendous potential in terahertz imaging, communications, non-destructive evaluation, and many other applications. [ABSTRACT FROM AUTHOR]