Optical transmission through a plasmon film lens with small roughness: enhanced spatial resolution of images of single source and multiple sources

We study image enhancement of transmitted optical fields though plasmon film lenses with smooth surfaces, random rough surfaces, and sinusoidal rough surfaces. We show that the silver film lens with subwavelength roughness provides image enhancement by reducing the spatial width of the image while preserving the image integrity. Images of multiple sources at random positions are enhanced, are spatial translational invariant for subwavelength spacing, and the quality of the enhanced images is preserved. Two numerical methods, namely, the method of moments and the T-matrix method, are used to calculate the theoretical results providing a validity check of the accuracy of the solutions. The analytic small perturbation method to arbitrary orders is utilized to demonstrate image enhancement effects in the spectral domain. The role of surface plasmon polaritons (SPPs) in plasmon imaging is explained and it is shown that the surface with subwavelength roughness enhances images by suppression of the SPPs. (C) 2011 Optical Society of America