A 3-D-Printed Metalens Composed of Composite Phase Units With Aligned Frequency Response for OAM-Enabled IoT Applications

This paper presents a novel composite phase unit (CPU) designed for an orbital angular momentum (OAM) metalens (ML), featuring a 3D-printed middle metal layer (MML) with non-uniform height. This design reduces slot length variations and mitigates bandwidth shrinkage resulting from passband overlap. It also aligns the frequency response of each CPU, ensuring that peak transmission occurs at the center frequency. The CPU consists of an MML sandwiched between two polarization grids (PGs), forming a quasi-Fabry-Pérot (FP) cavity. A high-resonance metal slot structure within the MML improves the transmission amplitude. To achieve a full 2π phase shift range, the CPU combines propagation, geometric, and resonant phase-control mechanisms. The non-uniform-height MML is fabricated via selective laser melting (SLM) using AlSi10Mg, which demonstrates the capability of 3D printing to fabricate complex structures. Experimental results show that the ML achieves a measured gain of 26.81 dBi at 36 GHz and a 3-dB gain bandwidth of 16.2%, representing significantly improved bandwidth retention relative to the CPU’s 3-dB transmission bandwidth of 12.8%. The proposed OAM metalens demonstrates high mode purity and stable transmission, which enables efficient multichannel wireless communications that are critical for Internet of Things (IoT) applications. This structure significantly improves link capacity, energy efficiency, and system-level simplicity in multichannel IoT systems.