Design studies of a far-field plasmonic superlens with an enlarged field of view

Abstract

Based on our previous studies, we numerically demonstrate imaging capability of a cascaded plasmonic superlens with an enlarged field of view for directly imaging subwavelength objects with magnification in the far field at a visible wavelength. The superlens consists of two plasmonic slabs. One is a plasmonic cavity lens for near-field coupling, and the other one is a planar plasmonic lens for phase retardation and thus image magnification is enabled. First, we investigate the superlens with an inverted plasmonic cavity structure (with respect to our previous design), which simplifies the nano-fabrication process. Then we design the planar plasmonic lens with an increased aperture size. Simulation results show that the superlens with the inverted structure can still achieve subwavelength imaging. Furthermore, a lateral resolution of 180 nm at the wavelength of 640 nm is manifested by the superlens with a larger field of view. When the aperture size of the planar plasmonic lens is doubled from 2.1 μm to 4.2 μm, the field of view of the superlens is increased by a factor of 1.4. The results provide a profound physical insight into the design of a cascaded plasmonic superlens system and pave the way for further experimental investigations.