title: Broadband acoustic cloak for ultrasound waves.
abstract: Invisibility devices based on coordinate transformation have opened up a new field of considerable interest. We present here the first practical realization of a low-loss and broadband acoustic cloak for underwater ultrasound. This metamaterial cloak is constructed with a network of acoustic circuit elements, namely, serial inductors and shunt capacitors. Our experiment clearly shows that the acoustic cloak can effectively bend the ultrasound waves around the hidden object, with reduced scattering and shadow. Because of the nonresonant nature of the building elements, this low-loss (∼6  dB/m) cylindrical cloak exhibits invisibility over a broad frequency range from 52 to 64 kHz. Furthermore, our experimental study indicates that this design approach should be scalable to different acoustic frequencies and offers the possibility for a variety of devices based on coordinate transformation.
authors.affiliation: Department of Mechanical Science & Engineering and the Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois 61801, USA.
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.forename: Chunguang
authors.initials: C
authors.lastname: Xia
authors.forename: Nicholas
authors.initials: N
authors.lastname: Fang