On the optimization of sub-wavelength aperture transmission

Surface plasmon polariton (SPP) enhanced aperture designs seem to open a new way to squeeze light beyond the fundamental diffraction limit [1-4]. In particular, it has been noted [1] that cylindrical corrugations around a single, central, sub-wavelength sized hole (cf., Fig. 1) in a metal film can enhance the otherwise weak transmission through the hole by a factor of three to five, due to the influence of SPPs excited by the corrugations. However, the corrugation designs presented thus far have been more or less optimized for relatively large central holes (diameter ~ 200 – 400 nm) in a thick metal film (~ 300 – 400 nm). In this paper, we present corrugation designs that differ from existing ones; these are optimized based on the results obtained from two-dimensional Finite Difference Time Domain (FDTD) simulations of the near field transmission of a single 50 nm wide slit in thin corrugated metal films (cf., Fig. 2).