Metamaterial frequency-selective superabsorber.

Using transformation optics a frequency-selective superabsorber can be constructed that consists of an absorbing core material coated with a shell of isotropic double negative metamaterial. For a fixed volume its absorption cross section can be made arbitrarily large at one frequency. The double-negative shell serves to amplify the evanescent tail of the high-order cylindrical waves, which induces strong scattering and absorption. Our conclusion is supported by both analytical Mie theory and numerical finite-element simulation. Interesting applications of such a device are discussed.