Multiple super-resolution imaging in the second band of gradient lattice spacing photonic crystal flat lens

Based on the triangular lattice two-dimensional photonic crystal (PC), the lattice spacing along the transverse direction to propagation is altered, and a gradient PC (GPC) flat lens is designed. The band structures and equal frequency curves of the GPC are calculated; then, the imaging mechanism and feasibility are analyzed. The imaging characteristics of the GPC flat lens are investigated. It is observed that the GPC can achieve multiple types of super-resolution imaging for the point source. This GPC lens is allowed to be applied to imaging and other fields such as filtering and sensing.