Subwavelength light focusing using random nanoparticles

There has been an escalation in interest in developing methods to control the near field because of its role in subwavelength optics. Many novel ideas have emerged in the field of plasmonics 1 , super-resolution optical imaging 2 , 3 , 4 , 5 and lithography 6 , among others. However, the near field generated in plasmonic metamaterials is fundamentally restricted by their predesigned structure, and super-resolution optical techniques do not directly control the near field. Here, we achieve direct control of the optical near field by shaping the wavefront impinging on turbid media consisting of random nanoparticles. The linear relation between input far field and scattered output near fields allows us to coherently control the near field at arbitrary positions. Direct control of the near field through scattering control offers novel approaches for subwavelength optics and may have direct applications in bio- and nanophotonics. Focusing beyond the diffraction limit is achieved by using elastic light scattering from a highly turbid medium to convert propagating far-field components into near-field wave vectors. This finding may open new avenues for the subwavelength control of light, with applications in nanolithography and the interconnection between nanoelectronics and nanophotonics.