Fractal plasmonic metamaterials for subwavelength imaging.

We show that a metallic plate with periodic fractal-shaped slits can be homogenized as a plasmonic metamaterial with plasmon frequency dictated by the fractal geometry. Owing to the all-dimensional subwavelength nature of the fractal pattern, our system supports both transverse-electric and transverse-magnetic surface plasmons. As a result, this structure can be employed to focus light sources with all-dimensional subwavelength resolution and enhanced field strengths. Microwave experiments reveal that the best achievable resolution is only lambda/15, and finite-difference-time-domain simulations demonstrate that similar effects can be realized at infrared frequencies with appropriate designs.