  A brief, tutorial account is given of the differences between the near and
far regions of the elec-tromagnetic field emphasizing the source-dependent
behavior of the former and the universal properties of the latter. Field
patterns of near-field plates, that is, metasurfaces used for sub-wavelength
applications, are discussed in some detail. Examples are given of fields that
decay away from the plates in an exponential manner, a ubiquitous feature of
many interface problems, and metasurfaces for which the decay is not
exponential, but algebraic. It is also shown that a properly designed system of
two parallel near-field plates can produce fields that exhibit pseudo minima,
which are potentially useful for near-field tweezer-like applications.

Optics;Classical Physics