Broadband Acoustic Cloak for Ultrasound Waves

TLDR

Invisibility devices based on coordinate transformation have opened up a new field of considerable interest. The study presents the first practical realization of a low‑loss, broadband acoustic cloak for underwater ultrasound. The cloak is built from a network of serial inductors and shunt capacitors forming a metamaterial that achieves low loss and broadband performance. Experiments show the cloak bends ultrasound around the hidden object, reducing scattering and shadow, achieving low loss (~6 dB/m) over 52–64 kHz, and indicating scalability to other frequencies.

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.