  A type of Tamm states inside metal-insulator-metal (MIM) waveguides is
proposed. An impedance based transfer matrix method is adopted to study and
optimize it. With the participation of the plasmonic Tamm states, fields could
be enhanced twice: the ffirst is due to the coupling between a normal waveguide
and a nanoscaled plasmonic waveguide and the second is due to the strong
localization and field enhancement of Tamm states. As shown in our 2D coupling
configuration, |E|^2 is enhanced up to 1050 times when 1550 nm light is coupled
from an 300 nm Si slab waveguide into an 40 nm MIM waveguide.
