Achieving sub-diffraction imaging through bound surface states in   negative-refracting photonic crystals at the near-infrared
  We report the observation of imaging beyond the diffraction limit due to bound surface states in negative refraction photonic crystals. We achieve an effective negative index figure-of-merit [-Re(n)/Im(n)] of at least 380, ~125x improvement over recent efforts in the near-infrared, with a 0.4 THz bandwidth. Supported by numerical and theoretical analyses, the observed near-field resolution is 0.47 lambda, clearly smaller than the diffraction limit of 0.61 lambda. Importantly, we show this sub-diffraction imaging is due to the resonant excitation of surface slab modes, allowing refocusing of non-propagating evanescent waves. 
R. Chatterjee, N. C. Panoiu, K. Liu, Z. Dios, M. B.Yu, M. T. Doan, L.   J. Kaufman, R. M. Osgood, and C. W. Wong