ABSTRACT
Control of electromagnetic (EM) flux and energy is a fundamental
scientific issue with great implications in theory and applications.
Based on the principles of refraction and reflection, lenses and
waveguides composed of dielectrics and metals have become the
most successful devices to guide and control EM waves and
fluxes. Recently, the rapid development in the field of artificial
EM structures such as photonic crystals, plasmonic structures, and
metamaterials has inspired new ways to control EM waves and
fluxes beyond traditional methods, leading to intriguing devices
such as superlens, hyperlens, invisibility cloaks, illusion devices, and
tunneling waveguides. In this chapter, we introduce a mechanism to
control the spatial distribution of either the electric or the magnetic
field instead of both fields. We demonstrate that EM fluxes can
be controlled in an almost arbitrary manner in wavelength and
subwavelength scales. Interestingly, the principle of flux control
in our method does not rely on surface waves as in the field of
plasmonics, but relies on the evanescent waves induced by the
strong anisotropy and designed inhomogeneity of media. Alongwith
the ability of controlling EM flux, such inhomogeneous anisotropic
media exhibit surprisingly robust high transmittance. Combining
with transformation optics, such high transmittance property can
be utilized to build waveguide devices with almost arbitrary shapes
and bending angles. As ourmethod only needs to control the electric
field instead of the magnetic field, it also provides an efficient
approach for flux control with nonmagnetic dielectric media.
