Effective generation of unidirectional SPP beam with arbitrary profile

The beam formation of SPPs is very important in plasmonics. Different SPP beams could be used for different purposes, such as SPP focusing, non-diffractive SPP wave propagation, efficient SPP coupling, and manipulating particles. Here, we present a straightforward and effective method for generating unidirectionally propagating SPP beams with arbitrary profile in both amplitude and phase by locating the Δ-shaped nanoantennas. The Δ-shape of the nanoantennas is used to achieve unidirectionality of SPPs and the locations of the nanoantennas are controlled to realize arbitrary profile of the excited SPP wave. As examples, several SPP launchers generating different SPP beams are designed with this method. The near-field distribution of the generated SPP beams are also experimentally characterized to validate the effectiveness of this method.