Imaging enhancement of a photonic crystal superlens due to a surface mode with a specific dispersion

We study the imaging process for a photonic crystal slab lens with a surface defect by the finite-difference-time-domain (FDTD) method. We demonstrate an odd surface mode with a specific dispersion curve in this system. The dispersion curve has an extreme point, which is corresponding to a slow light. If the working frequency is chosen at this extreme point the subwavelength resolution of image will be enhanced. Moreover, the subwavelength resolution of image is very sensitive to the position of this extreme point in the dispersion diagram. Longer interaction time and better field distribution may give a qualitative physical understanding for the enhancement of imaging quality.