Optical field enhancement with plasmon resonant Bowtie nanoantennas

Abstract

When light of wavelength λ is focused into a medium of refractive index n, the minimum spot size due to diffraction is on the order of λ/(2n). For example, at a wavelength of 405 nm, at the edge of the visible band, diffraction limits the minimum spot size to be greater than 100 nm. Near-field techniques based on the idea that light can be passed through a tapered metal-covered optical fiber, which acts as a cut-off waveguidewhen the guide diameter is less than λ/(2n), have made it possible to obtain spot sizes on the order of 50 nm with power transmission on the order of 10-3 to 10-6 of the incident power. Similarly, passing light through a small pinhole on the order of 50 nm diameter leads to a field intensity at the end of the guide which is greatly reduced from that of the incident field. © 2007 Springer.