Optimization of the Bowtie Gap Geometry for a Maximum Electric Field Enhancement
Optimization of the geometry of a metallic bowtie gap at radio frequency is presented. We investigate the geometry of the bowtie gap including gap size, tip width, metal thickness and tip angle at macroscale to find the maximum electric field enhancement across the gap. The results indicate that 90∘ bowtie with 0.06 λ gap size has the most |Et|2 enhancement. Effects of changing the permittivity and conductivity of the material across the gap are also investigated. NEC-2 simulations show that the numerical calculations agree with the experimental results. Since the design and fabrication of a plasmonic device (nanogap) at nanoscale is challenging, the results of this study can be used to estimate the best design parameters for nanogap structure. Different amounts of enhancement at different frequency ranges are explained by mode volume. The product of the mode volume and |Et|2 enhancement is constant for different gap structures and different frequencies.