Focusing of scanning light beams below the diffraction limit without near-field spatial control using a saturable absorber and a negative-refraction material

Phys Rev Lett. 2006 Jan 13;96(1):013902. doi: 10.1103/PhysRevLett.96.013902. Epub 2006 Jan 3.

Abstract

We show that a scanning light beam can be focused below the diffraction limit without the control of moving near-field elements using the combination of two main components: a light-controlled saturable absorber, which creates seed evanescent components from the beam, and a layer of negative-refraction material, which amplifies the evanescent waves. Focusing to spots with a FWHM in the range of 0.2-0.3 lambda is predicted. For slightly off-resonant input beams, an intensity-dependent phase shift leads to smaller spots.