Ideal boundary conditions and the generalized soft-and-hard surface

The electromagnetic ideal boundary is defined as a surface on which the complex Poynting vector has no normal component. Examples of such boundaries are the classical perfect electric and magnetic boundaries as well as the soft-and-hard surface. In the present study the most general isotropic and anisotropic ideal boundaries are introduced and the basic properties of plane-wave reflection from a planar boundary are studied in terms of incident plane waves. At the isotropic ideal boundary, an incident wave is reflected in two directions. A special self-dual ideal planar boundary has the interesting property as being a perfect back-reflector for a plane wave incident from any direction. An anisotropic ideal boundary can be labeled as a generalized soft-and-hard surface and it can be used to transform the polarization of an incident field to another one