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We report a new approach of in-plane diffractions of surface Plasmon polariton (SPP) that can tune the beam phase almost at will. It is developed by so-called “non-perfectly-matched” Bragg diffractions in a non-periodic nano-array with respect to a propagation SPP wave. With this approach, a 3/2-power phase modulation is obtained for a SPP beam, by which a well defined plasmonic Airy beam is experimentally achieved, exhibiting its unique properties, such as the non-dispersion, non-diffraction, self-bending, and self-healing. Due to the frequency tolerance of the non-periodic array structure, bicolor SPP Airy beams are demonstrated as well.

plasmonics; Airy-beam; diffraction