  Consider the transverse magnetic polarization of the electromagnetic
scattering of a plane wave by a perfectly conducting plane surface, which
contains a two-dimensional subwavelength rectangular cavity. The enhancement is
investigated fully for the electric and magnetic fields arising in such an
interaction. The cavity wall is assumed to be a perfect electric conductor,
while the cavity bottom is allowed to be either a perfect electric conductor or
a perfect magnetic conductor. We show that the significant field enhancement
may be achieved in both nonresonant and resonant regimes. The proofs are based
on variational approaches, layer potential techniques, boundary integral
equations, and asymptotic analysis. Numerical experiments are also presented to
confirm the theoretical findings.
