High-permittivity ceramics enabled highly homogeneous zero-index metamaterials for high-directivity antennas and beyond
Yue‐Yang Liu, Tian Dong, Xu Qin, Weijia Luo, Ning Leng, Yujing He, Yong Qiang Yuan, Ming Bai, Jingbo Sun, Ji Zhou, Yue Li, Yang Li
Abstract
Abstract Zero-index metamaterials (ZIMs) can support uniform electromagnetic field distributions at any frequency, but their applications are hampered by the ZIM’s homogenization level—only 3 unit cells per free-space wavelength, which is fundamentally limited by the low-permittivity inclusions ( ε r ≈ 12) and background matrix ( ε r ≈ 1). Here, by filling high-permittivity SrTiO 3 ceramic ( ε r ≈ 294) pillars in BaTiO 3 ( ε r ≈ 25) background matrix, we demonstrate a highly homogeneous microwave ZIM with an over threefold increase in the homogenization level. Leveraging such a ZIM, we achieve not only an antenna, approaching the fundamental limit in the directivity with outstanding scalability, but also a concave lens with a focal length of as short as 1 λ 0 . Our highly homogeneous ZIM has profound implications in ceramics, ZIM-based waveguides and cavities, free-space wavefront manipulation, and microwave quantum optics, and opens up enormous possibilities in wireless communications, remote sensing, global positioning satellites, etc.