Dielectric lens guides in-plane propagation of surface plasmon polaritons

In this work, we present in-plane propagation of surface plasmon polaritons (SPPs) guided by a single dielectric (Al 2 O 3 ) subwavelength lens. By mounting a designed Al 2 O 3 nanoparticle on the silver film, the effective index of a silver-Al 2 O 3 interface is influenced by the particle thickness, then the phase difference between the silver-air and silver-Al 2 O 3 interface can be utilized to modulate the in-plane propagation of SPPs. We show that an elliptical Al 2 O 3 lens transforms the diffusive SPPs into a collimated beam, whose direction of propagation and beam width can be easily controlled. We also present that a triangular Al 2 O 3 lens significantly reforms the SPPs to a Bessel beam, which possesses non-diffractive and self-healing properties. Our investigation provides unique way to guide the in-plane transport of SPPs by using dielectric subwavelength elements, which may achieve potential applications in plasmonic integrated circuits.