Double-Zero-Index Structural Phononic Waveguides

The recent development of double-zero-index metamaterials (with both $ϵ$ and μ ≈0) in photonics and acoustics has enabled exotic effects in wave manipulation, including tunneling, squeezing, and cloaking. This study presents the design, fabrication, and testing of an elastic waveguide with double-zero-index properties. This single-material design, featuring tapered locally resonant unit cells, is extremely simple to fabricate. With Dirac-like dispersion structures at the center of the Brillouin zone at the heart of its physics, this waveguide offers a means to control the flow of mechanical energy, such as vibrations and noise, in lightweight mechanical systems.