High‐Efficiency Transmissive Programmable Metasurface for Multimode OAM Generation

TLDR

Metasurfaces are widely studied for generating electromagnetic waves carrying orbital angular momentum, and programmable variants enable real‑time switching between multiple OAM modes, but existing reflective designs suffer from low efficiency and feed blockage. This work proposes a transmissive programmable metasurface to achieve highly efficient generation of multimode convergent OAM beams. The design uses electronically reconfigurable 1‑bit phase units built from two PIN diodes in the radiating layer, whose antisymmetric configuration yields nearly uniform transmission magnitude with inverted phase states across a wide band, allowing dynamic modulation of quantized code distributions to synthesize programmable multimode OAM beams. Simulations and measurements demonstrate the unit achieves 1‑bit phase tuning with a minimum insertion loss of 0.2 dB, a 2‑dB bandwidth exceeding 10 %, and confirm the effectiveness of the transmissive metasurface for multimode OAM generation.

Abstract

Abstract Metasurfaces have been extensively studied for generating electromagnetic waves carrying orbital angular momentum (OAM). In particular, programmable metasurfaces enable real‐time switching between multiple OAM modes in a digital manner. However, the current programmable metasurfaces are mostly based on reflective mode, which suffer from low efficiency as well as serious feed blockage. In this paper, a transmissive programmable metasurface is presented for the highly efficient generation of multimode convergent OAM beams. The proposed transmissive metasurface is composed of electronically reconfigurable units with 1‐bit phase resolution (0/π), which are obtained by integrating two PIN diodes in the radiating layer for current direction modulation. Through the antisymmetry configuration of the two PIN diodes, nearly uniform transmission magnitudes but inversed phase states in a wide band can be obtained. The simulation results show that the proposed reconfigurable unit can achieve good 1‐bit phase tuning, with minimum insertion loss of 0.2 dB and 2 dB transmission bandwidth of more than 10%. Through the dynamic modulation of the quantized code distributions on the metasurface, programmable multimode OAM beams can thus be constructed. Both simulated and measured results verify the effectiveness of the proposed design.