Launching of surface plasmon polaritons with tunable directions and intensity ratios by phase control of dual fundamental Gaussian beams

This study proposes a method to achieve excitation of surface plasmon polaritons (SPPs) with tunable directions and intensity ratios on a designed two thin slit structure by the phase control of dual fundamental Gaussian beams. Simply modulating the phase difference between two incident fundamental Gaussian beams (i.e. TEM_{0, 0} mode laser beam) controls the propagating direction of the resulting SPP wave between two opposite linear directions and also the value of the intensity ratio between propagating SPP waves in two opposite directions. The proposed method achieves a wide dynamic SPP intensity ratio adjusting range from-20 dB to 20 dB. This easy method of changing the direction of SPPs makes the dynamic control of the direction of SPP waves practicable, which shows great potential in plasmonic applications.