Generalized local analogue model for nonlocal plasmonic nanostructures based on multiple-fluid hydrodynamic framework

Spatial dispersion plays a critical role in nanophotonics when small plasmonic structures with feature sizes of few nanometers are handled. Such nonlocality is typically considered in a hydrodynamic framework and generally requires solving coupled partial differential equations, and therefore is involved. We develop a generalized local analogue model to reflect the nonlocal effects of plasmonic structures and avoid the complicated analysis within the multiple-fluid hydrodynamic framework, where more than one kind of charge carriers is considered. We show that spatial nonlocality can be represented by simply replacing the nonlocal surface region with an in-situ artificial local dispersive film. With such an elegant and simple-to-use alternative, the conventional analysis and simulations in the local regime acquire nonlocal capability, sufficient for a quantitative description of various plasmonic structures in nanoscale, rendering a much simpler process and great practical advantages in the numerical treatment.