Subwavelength imaging with opaque left-handed nonlinear lens
  We introduce the concept of subwavelength imaging with an opaque nonlinear left-handed lens by generating the second-harmonic field. We consider a slab of composite left-handed metamaterial with quadratic nonlinear response and show that such a flat lens can form, under certain conditions, an image of the second-harmonic field of the source being opaque at the fundamental frequency. 
Alexander A. Zharov, Nina A. Zharova, Ilya V. Shadrivov, and Yuri S.   Kivshar