Two methods are explained to exactly solve Maxwell's equations where
permittivity, permeability and conductivity may vary in space. In the
constitutive relations, retardation is regarded. If the material properties
depend but on one coordinate, general solutions are derived. If the properties
depend on two coordinates, geometrically restricted solutions are obtained.
Applications to graded reflectors, especially to dielectric mirrors, to
filters, polarizers and to waveguides, plain and cylindrical, are indicated.
New foundations for the design of optical instruments, which are centered
around an axis, and for the design of invisibility cloaks, plain and spherical,
are proposed. The variability of material properties makes possible effects
which cannot happen in constant media, e.g. stopping the flux of
electromagnetic energy without loss. As a consequence, spherical devices can be
constructed which bind electromagnetic waves
