Negative refraction effect in two-dimensional photonic crystals

A theoretical study of negative refraction in two-dimensional hexagonal and square lattice photonic crystals is presented in this paper. Using dispersion surfaces, an investigation of the two mechanisms of this unusual phenomenon is done. Photonic crystals exhibiting negative refraction can be used to realize integrated flat lenses in order to obtain imaging with sub-wavelength resolution surpassing the diffraction limit of the conventional lenses.