We introduce a novel type of surface waves that form at the edge of guiding
structures consisting of several concentric rings. Such surface waves rotate
steadily upon propagation and, in contrast to nonrotating waves, for high
rotation frequencies they do not exhibit power thresholds for their existence.
There exists an upper limit for the surface wave ro-tation frequency, which
depends on the radius of the outer guiding ring and on its depth.Comment: 13 pages, 4 figures, to appear in Optics Letter