Ultra-Wideband Transmissive Programmable Metasurface Enabled Near-Field Holography and Far-Field OAM Generation

Transmissive programmable metasurface can offer notable benefits for the precise agile manipulation of electromagnetic (EM) waves, which is a promising candidate for radar detection, wireless communications, and spectral imaging. However, most previous studies typically face the challenge of narrow bandwidth and are constrained by relatively simple and single functionality. Here, an ultra-wideband (UWB) transmissive programmable metasurface is proposed to conduct agile multifunctional EM modulation. The meta-atom is designed with a butterfly-shaped configuration and manipulated using two pin diodes, demonstrating high-efficiency transmission with low insertion loss less than 1 dB and stable phase difference of 180° from 15.77 to 28.59 GHz, ranging from Ku to Ka-band with a fractional bandwidth up to 57.7%. The transmissive programmable metasurface is further constructed, and its effectiveness for multifunctional EM modulation is verified both numerically and experimentally, which can conduct different functionalities, including near-field holographic imaging at lower-frequency Ku-band and far-field high-purity orbital angular momentum (OAM) generation at higher-frequency Ka-band. The proposed strategy may enrich the functionalities of programmable metasurfaces, as well as open a new pathway toward UWB multifunctional applications.