Abstract
With one or more constitutive parameters vanishing, zero-index media have attracted broad interest as they enable peculiar functionalities. Conventional approaches to realize zero-index media are strongly dependent on geometric parameters, and cannot be easily generalized to three-dimensional (3D) systems. In our research, we realize 3D double-zero-index media, which offer distinctive functionalities inaccessible to their 2D counterparts due to the fundamental changes in topology, in phononic crystals and photonic crystals. We fabricate an acoustic waveguide of 3D double-zero-index medium in form of a “periscope” with two 90o turns and observe the tunneling of a normally incident planar wave through the waveguide yielding undistorted planar wavefront at the waveguide exit. In electromagnetic waves, the transmission through a 3D double-zero-index medium is unaffected by its inner boundaries, but highly sensitive to its outer boundaries. We also report a novel zero-index medium that is robust to variations in the geometric parameters of artificial structures. The realization of such a zero-index medium depends on lattice symmetries rather than accidental degeneracies of different eigenstates.
Brief Biography
Dr. Changqing Xu is currently a professor of physics at Nanjing Normal University. He received B. S. in physics at Soochow University in 2011, M. S. in physics at Soochow University in 2014, and then Ph.D. in physics at Soochow University in 2017. After that, he worked as a postdoc fellow in Computer, Electrical and Mathematical Sciences and Engineering Division in KAUST until the end of 2022. In 2023, he joined the School of Physics in Nanjing Normal University as a Professor. Dr. Xu was awarded the “Jiangsu Specially-Appointed Professor” in 2023 by Jiangsu Education Department. His research interest includes photonic crystals, phononic crystals, and acoustic metamaterials. He has published over 20 papers in peer-reviewed journals, including Physical Review Letters and Science Bulletin.