Evolution of electromagnetic interference through nano-metallic double-slit.

We investigated the characteristics of the near- and far-field regions of the interference for nano-metallic double-slits using a two-dimensional finite-difference time-domain (FDTD) method. We have found that the patterns in the near-field region have a phase difference of pi with respect to those in the far-field region. A boundary, which separates the interference patterns of the two regions exists as a half circle and grows as the distance between the two slits increase. It is also found that evanescent waves can be enhanced and confined by coating the double-slit with a dielectric cladding.