Imaging by photonic crystal without negative refraction

Diverse imaging of point source by a two-dimensional photonic crystal slab with square lattice is studied by the finite-difference time-domain method. Given proper frequencies, there seems to be some special directions like channels guiding the light propagation inside the photonic crystal, along which some images will be created. Although a frequency employed is within the range of resulting negative refraction according the view of [1], the behavior of negative refraction can not been found. It is suggest that except negative refraction there should be multiple mechanisms making point image by two dimension photonic crystal slab.