Figure 3. Nano antenna optimization and near-field intensity variation with gap size.

(a) The near field intensity enhancement for several bowtie antennas with a gap of 50 nm is plotted against antenna length (green axis) and half bow angle (blue axis). For a gap of 50 nm, an enhancement factor of 4 × 10⁴ was achieved for 2.7 μm length and 50° bow angle. (b) Numerical simulation of the optimized bowtie dipole versus different gap sizes. The plotted relative intensity enhancement is defined as the ratio between the electric field intensity at the middle of the gap to the electric field intensity of the incident plane wave. (c) Simulated relative near field intensity enhancement for the optimized bowtie of a 50 nm gap. (d) Simulated relative near field intensity enhancement for the optimized bowtie of a 10 nm gap.