Finite-boundary bowtie aperture antenna for trapping nanoparticles

Abstract

We have found that a single finite-boundary bowtie aperture (FBBA) antenna with gap separation of 10nm between its tips is capable of confining the electric field to a 18nm * 18nm region (̧=39:4) at 5nm beneath the gold film and enhancing its near- field intensity by 1,800-fold inside the gap. The FBBA antenna is thus able to provide enhanced trapping potential by virtue of such extraordinarily high (but exponentially decaying) optical near-fields. We have been able to show that 12nm gold nanoparticles can, in principle, be trapped by the FBBA antenna with 20nm gap separation; stable trapping is assured where the trapping potential is found to be several times higher than Brownian-motion potential in water. In addition to trapping nanoparticles, this simple but efficient FBBA antenna may find application in near-field optical data storage.