Focusing surface plasmons to multiple focal spots with a launching diffraction grating

We propose a surface plasmon launching diffraction grating (SPLDG) to obtain multiple focal spots of SPs with nearly equal intensity. The SPLDG is composed of grooves that are located on concentric arcs, whose projections on the chord form a grating. When the incident plane wave illuminates the grating, SPs launched and diffracted into different directions will be approximately focused to multispots on a circle. Here, we obtain three and five focuses and the numerical simulation agrees well with the experiment.Physics, AppliedSCI(E)EI14ARTICLE11null9