Superfocusing of light below the diffraction limit by photonic crystals with negative refraction

Usual optical elements cannot focus a light beam to a spot with diameter smaller than half of the wavelength of the light; however overcoming this limit is of great importance in several applications in high-tech, such as optical lithography or magneto-optical date storage and numerous other fields of science and industry. Here we show that it is possible to focus light to spots below the diffraction limit (superfocusing) by the combination of two main elements: one which creates weak near-field evanescent components of the beam, like a wavelength-scale aperture, and an amplifier of these evanescent fields, like a slab of a photonic crystal with negative refraction.