Design and analysis of bow-tie aperture with strong near-field enhancement effect

In this paper the near-field distributions of bow-tie apertures in visible range are characterized by the method of 3D finite-difference time-domain (FDTD). The numerical simulation results reveal theoretically the relation of field enhancement effect of bow-tie aperture and its several parameters including tip angle, aperture size and film thickness. For the bow-tie aperture with a certain tip angle, the metallic film’s thickness can be firstly determined at its resonant peak, and then the aperture size can be determined at a tradeoff between the field enhancement and the field distribution. The calculation results of the transformed bow-tie apertures indicate that the transformation at tip angle will bring an obvious change to light field distribution. The bow-tie aperture can be directly used as an exit aperture of a very small aperture laser (VSAL) or as an unattached shield, to produce a sub-wavelength light source with high transmission. It is possible to be used in near field super-resolution imaging, high-density optical data storage, nano-photolithograhy and so on.