Higher-Order Resonant Power Flow Inside and Around Superdirective Plasmonic Nanoparticles
The optical power flow around a plasmonic particle has been a topic of research interest over the years [see e.g., C. F. Bohren, Am. J. Phys. 51, 323 (1983); V. A. Bashevoy, V. A. Federov, and N. I. Zheludev, Optics Express, 13, 8372 (2005)]. Here we revisit this problem with an emphasis on higher-order resonances, and we present the theoretical results of our analysis for such power flow distribution for plasmonic nanoparticles at their multipolar resonances. Results for the second and third orders of resonances show optical power flow patterns that are significantly different from that of the first-order resonance inside and around plasmonic superdirective nanoparticles, with multi-center vortices, saddle points and saddle lines, and with an anomalous circulation of power resembling higher-order modes in a resonant cavity. A potential application of these optical flow patterns to trap or move a neighboring nanoparticle is also briefly suggested.