We demonstrate that a hexagonal two-dimensional photonic crystal can act as an isotropic medium with an effective refractive index $n_{\mathit{eff}}=-1$, therefore capable of unrestricted subwavelength lensing. We study the lensing by calculating the photonic band structure and the propagation maps of the electromagnetic waves through slabs of the photonic crystal. We investigate the surface and the crystal disorder effects on the lensing by analyzing the light intensity profile at the image of a line source. Finally, we show that the surface mode of the slab can be excited, which facilitates the subwavelength lensing effect in our photonic crystals.

• Received 23 July 2004

DOI:https://doi.org/10.1103/PhysRevB.71.085101