Double plasmon resonance in spherical metal-dielectric-metal nanostructures

Results are presented from numerical simulations of the optical properties of spherical nanostructures consisting of a metal core and two shells—dielectric and metal. A study is made of nanostructures with Ag, Al, and Cu cores and an outer Ag shell. It is shown that, for certain ratios between the radii of the structure components, the plasmon resonance of the metal core and that of the metal shell can occur at the same spectral position, with resulting increases in the local electromagnetic field amplitude within the nanostructure by a factor of 103–104 and in the absorption cross section by a factor of up to 103.