Influence of unit cell rotated on the focusing in a two-dimensional photonic-crystal-based flat lens

Focusing in photonic crystal (PC) slab has been studied theoretically and experimentally. PCs are composed of a unit cell repeated periodically. In this article, we investigate in detail the influence of the continuous rotation of the unit cell on the focus in a two-dimensional photonic-crystal-based flat lens by the finite-difference time-domain method and experimental measurement. It is found that the focusing can appear within a large range of rotated angle of the unit cell. When the rotation exceeds a certain angle, the focusing disappears. However, it is interesting that the focusing does not depart from the symmetric center because of rotation of the unit cell. (c) 2007 American Institute of Physics.