Gain-Assisted Poynting-Vector Vortices Realized With a Single Lossy Metal Wire

We examine electromagnetic waves propagating on the cross-sectional plane of a single cylindrical metal nanowire. For continuous waves to be sustained, gain medium is placed around the periphery of wire, thus compensating for the material loss of metal. The thickness of gain layer is assumed to be infinitely thin, whereby a threshold gain is defined as the jump in the radial component of Poynting energy. Resulting energy-flow patterns exhibit resemblance to atmospheric typhoon, but with a relative quietness within its eye region. In addition, we analyze optical-compressor aspects of the resulting swirl flows. On theoretical sides, we focus on the spatially transverse features of angular propagations associated with asymmetry, which arises in turn from the temporal irreversibility of Drude model for metal. Besides, we find relationships of vector and scalar potentials to Poynting vectors.