The paper discusses the reason why the image resolution can be significantly enhanced by the superlens with anti-reflection and phase control coatings (ARPC-superlens) via analyzing the surface plasmons (SPs) modes. ARPC-superlens is an asymmetric structure with finite thickness, in which we first find that there are two asymmetric SPs modes. By comparing the dispersion curve of SPs of ARPC-superlens and the SPs group velocity with their counterparts in the metric ones, we find that the Up Asymmetric Mode and Down Asymmetric Mode are excited within the ARPC-superlens with asymmetric structure. By simulating the aerial images in different SPs modes, the paper also discusses the optimal ratio between the metal slab and the ARPC coatings thickness. The results demonstrate that the subwavelength resolution of ARPC-superlens in Down Asymmetric Mode has been enhanced, when the metal/ARPC thickness ratio is 2:1.
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