Demonstrating a two-dimensional-tunable surface plasmon polariton dispersion element using photoemission electron microscopy

Functional elements of propagating surface plasmons are becoming increasingly significant for the development of plasmonic devices. To the best of our knowledge, the dispersion element of two-dimensional (2D) femtosecond surface plasmon polaritons (SPPs) as its central importance for future nano-optical circuits has never been reported. Here, we first demonstrate that the trench structure can act as a 2D-tunable SPP dispersion element by imaging the noncollinear mode using photoemission electron microscopy (PEEM). Experimental results show that directed propagation of SPPs can be controlled by varying the polarization direction of the femtosecond laser, and, more importantly, it is found that the actual propagation direction of the dispersed SPPs is directly obtained by reading PEEM images of SPPs using the noncollinear excited method in an Ag film. The experimental results are in agreement with classical 2D wave simulations. The results have demonstrated that the trench structure has potential as a tunable plasmonic dispersion element.