On the performance of plasmonic meniscus lenses for surface plasmon focusing

In this work, we present the design process and response of an ultra-compact plasmonic meniscus lens for Surface Plasmon Polariton (SPP) focusing. To design the lens, we adapted the lens maker equation (a classical optics technique) by introducing the concept of effective media for SPPs traveling within different multilayered media. This adapted equation was then exploited to design a convex-concave lens, also known as a positive meniscus lens, for use in plasmonics. The lens was designed by placing a meniscus-shaped block of silicon nitride (Si3N4) on top of a semi-infinite slab of gold (Au). The performance of the lens is evaluated in detail in terms of the power enhancement, depth of focus, and spatial resolution of the focus. Moreover, the lens robustness is studied using off-axis illumination along with its spectral response, demonstrating how the adapted lens maker equation can be used in the design of such plasmonic meniscus devices.