Super imaging with a plasmonic metamaterial: Role of aperture shape

Through analyzing the transmission properties of metallic plates with periodic arrays of subwavelength apertures in different shapes, we found two conditions for such structures to work as super lenses. The working wavelength dictated by the aperture's shape resonance should be much larger than the array's periodicity, meanwhile the coupling between the aperture's waveguide modes and external radiations should be as small as possible. These two conditions contradict with each other for a square-shape aperture so that high index materials should be inserted into the apertures, while a fractal-shape aperture satisfies these two conditions simultaneously without using high-index insertions. Numerical simulations were performed to illustrate the imaging properties of these plasmonic lenses.

► We analyzed the transmission properties of metallic plates with periodic arrays of subwavelength apertures in different shapes.
► We found two conditions for such structures to work as super lenses.
► These two conditions contradict with each other for a square shape.
► A fractal-like shape satisfies these two conditions simultaneously without using high-index insertions.
► Numerical simulations were performed to illustrate the imaging properties of these plasmonic lenses.