Spatial filtering using media with indefinite permittivity and permeability tensors

Bilayers of media for which the permittivity and permeability tensors are indefinite-that is, not all principle elements possess the same sign-can be used to construct low-, high-, and bandpass spatial filters. These filters possess sharp adjustable roll-offs, and can operate both below and above free-space cutoff to select specific spatial variation components or beam angles from a source or image. (C) 2003 American Institute of Physics.