Tapered labyrinthine acoustic metamaterials for coherent controlling of acoustic wave

Acoustic metamaterials with their exotic material properties enable unprecedented control over acoustic wave propagation and reflection. Besides utilizing locally resonating structures or non-resonant composite effective media, non-locally resonating spatial coiling structures have recently been adopted to design negative or high positive refractive index metamaterials. We have in the past experimentally demonstrated the unit cell characteristics of one kind of labyrinthine metamterial (Xie et al. PRL 2013) and its impedance matching improved versions (Xie et al. APL 2013). In this work, we present several coherent modulation devices based on our recently proposed tapered labyrinthine metamaterials. With thickness of only one or two metamaterial cell layers, we can create an acoustic blazed diffraction grating, a phase conjugation lens, or a flat lens that can perform plane wave-cylindrical wave conversion. The design process and experimental demonstrations will be presented. The coherent controlling devi...