Deformable broadband metamaterial absorbers engineered with an analytical spatial Kramers-Kronig permittivity profile

Electromagnetic (EM) materials with perfect absorption have long been investigated for their important applications in many practical technologies. The trial-and-error method has been mostly employed to achieve this target, either by varying the constituent compositions for traditional natural material absorbers or by running computer simulations for general metamaterial (MM) absorbers. In this work, the authors propose a new method with analytical guidance to build omnidirectional perfect absorbers inspired by the recently proposed spatial Kramers-Kronig (KK) nonreflecting dielectric profile. The subtle combination of the spatial and time dispersions in the metamaterial-engineered KK profile gives the desired broadband response property. More importantly, these features remain invariant when the sample is uniformly compressed or stretched with large thickness change, i.e., this particular broadband absorber is deformable, which has been firstly reported in the literature. The current results will pave a new way to design high-efficiency EM absorbers that could also be extended in general to manipulate waves for other fields or applications.