1 Department of Photonics Engineering, Technical University of Denmark2 Structured Electromagnetic Materials, Department of Photonics Engineering, Technical University of Denmark3 Center for Nanostructured Graphene, Center, Technical University of Denmark
The plasmon response of metallic nanostructures is anticipated to exhibit nonlocal dynamics of the electron gas when exploring the true nanoscale. We extend the local-response approximation (based on Ohm's law) to account for a general short-range nonlocal response of the homogeneous electron gas. Without specifying further details of the underlying physical mechanism we show how this leads to a Laplacian correction term in the electromagnetic wave equation. Within the hydrodynamic model we demonstrate this explicitly and we identify the characteristic nonlocal range to be ξNL∼vF/ω where vF is the Fermi velocity and ω is the optical angular frequency. For noble metals this gives significant corrections when characteristic device dimensions approach ∼1–10nm, whereas at more macroscopic length scales plasmonic phenomena are well accounted for by the local Drude response.
Photonics and Nanostructures, 2013, Vol 11, Issue 4, p. 303-309
Nanoplasmonics; Nonlocal response; Hydrodynamic model