Focusing of light by disordered metamaterials

In many disordered composite materials, such as paint, powders and biological tissue, light is scattered randomly and the directionality of the light is lost. In these disordered metamaterials, light normally performs a random walk and emerges as a random interference pattern known as speckle. Using continuous wave light with a perfectly matched wavefront, we make these disordered materials focus light as sharply as a lens. The matched wavefront is constructed using feedback from a detector in the target focus. By changing the incoming wavefront, we control the position and shape of the focus.