Controllable optical negative refraction and phase conjugation in graphite thin films

Optical metamaterials have demonstrated remarkable physical properties, including cloaking, optical magnetism and negative refraction(1-3). The last of these has attracted particular interest, mainly because of its promise for super-resolution imaging(4,6). However, the widespread use of negative refraction at optical frequencies is challenged by high losses and strong dispersion effects, which typically limit operation to narrow frequency bands(7). Here we use degenerate four-wave mixing to demonstrate controllable negative refraction at a graphite thin film, which acts as a highly efficient phase-conjugating surface. The scheme has very low loss because of the negligible thickness of the nonlinear material and it ensures broadband operation due to the linear band structure of graphene.