Negative refraction and sub-wavelength imaging using transparent   metal-dielectric stacks
  Negative refraction is known to occur in materials that simultaneously possess a negative electric permittivity and magnetic permeability; hence they are termed negative index materials. However, there are no known natural materials that exhibit a negative index of refraction. In large part, interest in these materials is due to speculation that they could be used as perfect lenses with superresolution. We propose a new way of achieving negative refraction with currently available technology, based on transparent, metallo-dielectric multilayer structures. The advantage of these structures is that both tunability and transmission (well above 50%) can be achieved in the visible wavelength regime. We demonstrate both negative refraction and superresolution in these structures. Our findings point to a simpler way to fabricate a material that exhibits negative refraction. This opens up an entirely new path not only for negative refraction, but also to expand the exploration of wave propagation effects in metals. 
Michael Scalora, Giuseppe D'Aguanno, Neset Akozbek, Marco Centini,   Domenico de Ceglia, Mirko Cappeddu, Nadia Mattiucci, Jo...