Tunable plasmonic focus array generated by Dammann grating in tightly focusing system

Abstract

Surface plasmon polaritons (SPPs) play crucial roles in a wide-range of applications, such as plasmonic imaging, sensors, plasmonic tweezers, etc. However, the excitation of SPPs gives rise to a big challenge to manipulate SPP fields in a dynamical way. Here, we propose a full optics-controlled method to manipulate SPP fields with Dammann grating (DG) in a tightly focusing system, rather than customizing a special structure on the metal film. Owing to the coupling between free-space incident vector beam and SPPs, the phase of SPPs can be controlled directly by that of the incident vector beam, which is modulated by the DG in free space. Thus, by adjusting the parameters of the DG, a plasmonic focus array with tunable number, position and topological charge can be created flexibly on the metal film, while the light intensity distribution of each plasmonic focus is only dependent on the polarized state of the incident vector beam. This work presents an important step for the manipulation of SPP fields with wavefront techniques and may open new avenues to extend holography for dynamical SPP field control.