Extraordinary acoustic scattering in a periodic PT-symmetric zero-index metamaterials waveguide

¹ Jiangsu Key Laboratory of Opto- Electronic Technology, School of Physics and Technology, Nanjing Normal University Nanjing 210023, China
² Key Laboratory of Modern Acoustics of MOE, Department of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University - Nanjing 210093, China

^(a) weiqi@njnu.edu.cn
^(b) wudajian@njnu.edu.cn

Received: 17 January 2019
Accepted: 6 March 2019

Abstract

We propose an acoustic waveguide consisting of periodic parity-time-symmetric zero-index metamaterials separated by layers of passive medium. Consistent analytical derivations and numerical simulations show that a rich variety of extraordinary scattering effects can be achieved. For example, unidirectional transparency is found to occur at an exceptional point. At singular points, the system behaves as an acoustic coherent perfect absorber (CPA) laser. Bidirectional transparency, induced by the Fabry-Pérot resonance or balanced dissipation and amplification, is also observed. In contrast to the previous scheme without structural periodicity, the proposed periodic structure allows a greater number of conditions under which the CPA laser behavior and bidirectional transparency can be achieved, which may facilitate the experimental realization of such extraordinary effects.