An apparatus including a three dimensional sub-wavelength structure for electromagnetic applications including a surface layer formed of a metal or semiconductor film, one or more additional layers stacked to the surface layer, one or more sub-wavelength apertures in the surface layer, and one or more cavities nearby the one or more sub-wavelength apertures. The size of each aperture is smaller than the wavelength of the electromagnetic field incident upon the three dimensional sub-wavelength structure. The one or more cavities provide accessibility for a dielectric material within and below each aperture. Each cavity may also contain at least one metal or semiconductor sub-wavelength particle. A method of fabricating a three dimensional sub-wavelength structure is also provided.