Figure 2. Angular radiation patterns for beam steering device consists of spiral plasmonic antenna and ZnS substrate with different displacements.

For zero displacement: (a, b) line-scans in the x-z and y-z planes. For x-directional displacements of 50 nm, 100 nm, 150 nm and 200 nm: (c, d, g, h) line-scans in the x-z plane. For y-directional displacements of 50 nm and 100 nm: (e, f) line-scans in the y-z plane.