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

Abstract

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.

Extraordinary transmission through a silver film perforated with bowtie-shaped aperture array in midinfrared region

“…Numerous studies have simulated the far-field and near-field pattern of electromagnetic wave penetrating through the bowtie shaped aperture, the excitation radiation intensity shows great dependence on gap size, tip angles and beam size. [7][8][9] Other research groups also provided experimental results which demonstrated polarization characteristic 10 and plasmonic resonance involved in this kind of structure. 11 It is well understood that one can easily choose the suitable geometrical parameters of bowtieshaped aperture to meet the requirements.…”