Three-dimensional plasmonic nanofocusing

We demonstrate three-dimensional plasmonic nanofocusing of light with patterned metallic pyramids obtained via template stripping. Gratings on the faces of these pyramids convert linearly polarized light into plasmons that propagate toward and converge at a ∼10 nm apex. Experiments and computer simulations confirm that optical energy is focused into a nanoscale volume (5 - 10⁵ wavelength³). Because these structures are easily and reproducibly fabricated, our results could benefit many applications, including imaging, sensing, lithography, and nonlinear spectroscopy.