Acoustic Equivalent Lasing and Coherent Perfect Absorption Based on a Conjugate Metamaterial Sphere

Acoustic Negative Refraction and Planar Focusing Based on Purely Imaginary Metamaterials

Acoustic purely imaginary metamaterials (PIMs) contain loss and gain uniformly distributed in space, but in different parameters. Therefore, the PIMs contain the elements of gain and loss simultaneously. As a result, some extraordinary wave modes may appear depending on whether gain or loss elements dominate. In this work, we theoretically and numerically investigate the general excitation conditions for acoustic lasing, coherent perfect absorption (CPA) and for their co-existence in the framework of acoustic PIMs. All-angle negative refraction and planar focusing are achieved by pairing two PIM slabs with conjugating parameters. The proposed structure provides an alternative basis for possible applications of acoustic perfect imaging.