The metallic superlens typically shows two peaks in its transfer function related to the long- and the short-range surface plasmon polariton (SPP) modes. These peaks are necessary to amplify the evanescent waves compensating the exponential decays, but enhance the spatial frequencies disproportionally, resulting in strong sidelobes in the image. We propose to design the metallic superlens with close to the cutoff condition of the long-range SPP mode to balance the SPP amplification and the flatness of the transfer function, and thus eliminating the sidelobes in the image. The design experiments for the Al superlens at 193 nm with both the transfer-matrix approach and the numerical finite difference in time domain method are shown.
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