On extending the concept of double negativity to acoustic waves

INTRODUCTION At this moment, novel concepts of “negative” media, having negative refraction and/or “double negativity” and their physical consequences and plausible applications are drawing considerable at- tention from the science and engineering community. In the past few years, considerable progress has been made in electromagnetic (EM) waves. It is our wish to generalize such concepts to acoustic waves. Since the concept of negative refraction, negative constitutive relationships…

On extending the concept of double negativity to acoustic waves

The realization of double negative electromagnetic wave media, sometimes called left-handed materials (LHMs) or metamaterials, have drawn considerable attention in the past few years. We will examine the possibility of extending the concept to acoustic waves. We will see that acoustic metamaterials require both the effective density and bulk modulus to be simultaneously negative in the sense of an effective medium. If we can find a double negative (negative density and bulk modulus) acoustic medium, it will be an acoustic analogue of Veselago’s medium in electromagnetism, and share many novel consequences such as negative refractive index and backward wave characteristics. We will give one example of such a medium. Project (No. CA02/03.SC01) supported by Research Grant Council (RGC) Hong Kong, China