Fishnet metamaterial with double negative refractive index in blue region of visible spectrum

By optimizing the shape and scale of perforations as well as the depth of different layers, we obtained a metal- dielectric-metal double fishnet metamaterial with an unbroken 38-nm bandwidth of negative refractive index in visible spectrum, spaning from 459 to 497 nm. Moreover, the real parts of permittivity and permeability of this metamaterial are simultaneously negative from 460 to 478 nm in wavelength, reaching a frequency band as high as to the blue region - a territory that has never been explored before in visible spectrum.