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. (C) 2004 Optical Society of America.