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 (Al₂O₃) subwavelength lens. By mounting a designed Al₂O₃ nanoparticle on the silver film, the effective index of a silver-Al₂O₃ interface is influenced by the particle thickness, then the phase difference between the silver-air and silver-Al₂O₃ interface can be utilized to modulate the in-plane propagation of SPPs. We show that an elliptical Al₂O₃ 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 Al₂O₃ 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.