The use of plasmonics in light beaming and focusing

This paper reviews the use of plasmonics to shape light spatially in air and to focus surface plasmon polaritons (SPPs) on a metal surface. Methods to transform SPPs into spatially collimated or focused light by using surface gratings attached around a sub-wavelength slit or modulating the phase of the emitted light from multiple slits are discussed. In addition, it is shown that SPPs passing through diffractive slit patterns, a hole array, or an arc-shape slit can be used to generate focal spots on a metal surface. Before discussing those methods, the basics of SPPs are also briefly reviewed, in order to better understand the handling of SPPs.