Non-Bloch plasmonic stop-band in real-metal gratings.

Recent studies of plasmon surface wave (PSW) propagation in short-period perfectly conducting gratings have shown formation of stop-band that are not linked to the interaction between two (counter) propagating surface waves. We study the properties of this stop-band in real metals. While for both perfectly conducting and real metals the propagation constant of PSW grows with the groove height, the stop-band in real metals appears for groove heights significantly smaller than in perfect metals. A physical explanation of the formation of the stop-band is proposed both by using a homogenisation of the corrugated layer and by analysis of the tangential electric field component.