The scattering of surface plasmon polariton (SPP) waves can be manipulated by various plasmonic structures. The plasmonic structure composed of arranged subwavelength nanobumps on a gold thin film is the promising structure to manipulation SPP wave. By controlling the geometric shape of the structures, the height, position, and pattern of scattered light from SPP wave can be modulated as desired. A clear single focusing spot can be reconstructed at a specific altitude by a particular curved structure with appropriate curvature and adjacent interspacing of nanobumps. The designed light patterns reconstructed by the focusing spot from the arranged curved structures at a specific observation plane are clearly demonstrated.
Nanobump structures are fabricated on the gold thin film by femtosecond laser direct writing (fs-LDW) technique. The
height and diameter of the gold nanobump are about 30nm, and 400 nm, respectively. The scattering light of surface
plasmon wave radiated from a nanobump is observed using a total internal reflection microscopy. A quarter-circle
structure composed of nanobumps is designed and produced to manipulate scattering light into specific pattern: The
focusing and diverging of the quarter circular structure in three dimensional space are demonstrated. The polarization
properties of focusing spot are also examined.