Space–Time Surface Plasmon Polaritons: A New Propagation-Invariant Surface Wave Packet

• DOI: 10.1021/acsphotonics.0c00293
• Publication Date: 2020-04-10T15:41:58Z
• Authors: Kenneth L. Schepler; Murat Yessenov; Yertay Zhiyenbayev; Ayman F. Abouraddy
• Keywords: Group velocity; Superluminal motion

We introduce the unique class of propagation-invariant surface plasmon polaritons (SPPs) representing pulsed wave packets propagating along unpatterned metal–dielectric interfaces and are localized in all dimensions, with potentially subwavelength transverse spatial widths. The characteristic features such linear diffraction-free, dispersion-free "plasmonic bullets" stem from tight spatiotemporal correlations incorporated into SPP spectral support domain, we thus call them "space-time" SPPs. show that group velocity space-time can be readily tuned to subluminal, superluminal, even negative values by tailoring field structure independently any material properties. present an analytical framework numerical simulations for propagation SPPs comparison traditional whose temporal degrees freedom separable, thereby verifying propagation-invariance former.