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.

► An odd surface mode is believed to bring more contributions to the subwavelength imaging process.
► An influence of dispersion curve shifting on the imaging resolution is studied.
► A better subwavelength resolution is found when the position of the surface state is approaching the light line in the dispersion diagram.