Enhancement of surface plasmon polariton excitation via feedback-based wavefront shaping.

Surface plasmon polariton (SPP) is an electromagnetic excitation with efficient spatial confinement and high local field intensity at a metal/dielectric interface, which has been widely applied in many fields such as nanophotonics, imaging, biosensing, nonlinear optics, and so on. However, the destructive interference, which arises from wavevector mismatching between the spatial components of incident light and SPP, limits the effective excitation of SPP. Here, we experimentally demonstrate the enhancement of SPP excitation via a feedback-based wavefront shaping method in the Kreschmann configuration. After optimizing the phase profile of the incident laser beam, the intensity is enhanced by a factor of 1.58 times even at the resonance angle of the fundamental mode Gaussian beam. Besides, the influences of different conditions for the enhancement of SPP excitation are also analyzed. This work provides a flexible and convenient method to further enhance the SPP excitation, and it may have the application of further enhancement of the interaction between SPP and other physical processes.