Birefringent left-handed metamaterials and perfect lenses
  We describe the properties of birefringent left-handed metamaterials and introduce the concept of a birefringent perfect lens. We demonstrate that, in a sharp contrast to the conventional left-handed perfect lens at $\epsilon=\mu=-1$, where $\epsilon$ is the dielectric constant and $\mu$ is the magnetic permeability, the birefringent left-handed lens can focus either TE or TM polarized waves or both of them, allowing a spatial separation of the TE and TM images. We discuss several applications of the birefringent left-handed lenses such as the beam splitting and near-field diagnostics at the sub-wavelength scale. 
Alexander A. Zharov, Nina A. Zharova, Roman E. Noskov, Ilya V.   Shadrivov, and Yuri S. Kivshar