Omnidirectional perfect acoustic cloak realized by homogeneous materials

Abstract

Acoustic cloaks derived by coordinate transformation have opened up a new field of considerable interest in the last two decades. However, since perfect omnidirectional acoustic cloak relies on inhomogeneous and anisotropic materials that posses extreme values in certain regions, this cloak was deemed impossible to be attained even with metamaterials. Recently, our group was competent to introduce a new kind of extreme acoustic material, named as acoustic null medium (ANM), for attaining various devices. In this letter, an extreme mapping function is exploited to achieve an omnidirectional acoustic cloak. The attained extreme homogeneous material through this transformation becomes ANM that can satisfy the extreme parameters requirement and as a result, can hide the object from any incident acoustic waves. Several numerical simulations were carried out to demonstrate the capability of the propounded cloak in cloaking objects from sound fields. The propounded work will pave the way towards cloaking arbitrary objects from any incident angle and obviate the conventional challenges regarding this device.