We identify a route towards achieving a negative index of refraction at optical frequencies based on coupling between plasmonic waveguides that support backwards waves. We show how modal symmetry can be exploited in metal-dielectric waveguide pairs to achieve negative refraction of both phase and energy. Control of waveguide coupling yields a metamaterial consisting of a one-dimensional multilayer stack that exhibits an isotropic index of - 1 at a free-space wavelength of 400 nm. The concepts developed here may inspire new low-loss metamaterial designs operating close to the metal plasma frequency.

H.J. Bakker (Huib)
Phys. Rev. Lett.
Photonic Materials

Verhagen, E., de Waele, R., Kuipers, K., & Polman, A. (2010). Three-dimensional negative index of refraction at optical frequencies by coupling plasmonic waveguides. Phys.Rev.Lett., 105(Article number: 223901), 1–4. doi:10.1103/PhysRevLett.105.223901