Superlensing effect without obvious negative refraction

The superlensing phenomenon of light in photonic-crystal lens-like structures of finite sizes was studied. The wave field was calculated by using the multiple scattering method. The influences of the shapes and interior structures of the lens-like devices on their imaging characteristics were carefully examined numerically. The numerical results revealed that negative refraction is not directly related to the subwavelength imaging phenomenon. For the photonic crystal slab of square-lattice type, superlensing effect was found to be essentially a near field effect.