Abstract
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.
Highlights
Plasmonic integrated systems have great potentials in small scale integration, fast and sensitive detection, so there are many ongoing research efforts to realize nanoscale plasmonic circuits capable of manipulating light below the diffraction limit [1,2,3]
In this work, we present in-plane propagation of surface plasmon polaritons (SPPs) guided by a single dielectric (Al2O3) subwavelength lens
We show that an elliptical Al2O3 lens transforms the diffusive Surface plasmon polaritons (SPPs) into a collimated beam, whose direction of propagation and beam width can be easily controlled
Summary
Plasmonic integrated systems have great potentials in small scale integration, fast and sensitive detection, so there are many ongoing research efforts to realize nanoscale plasmonic circuits capable of manipulating light below the diffraction limit [1,2,3]. Most attempts focus on the development of highly confined SPPs [26,27,28], different methods that can control the propagation of SPPs on extended metallic surfaces are crucial for realizing plasmonic integrated circuits [11, 29]. When an Al2O3 structure is mounted on a silver surface, the effective indices of the silver-air and silver-Al2O3 surfaces are different, providing a phase difference for the propagation of SPPs. We first analyze the effective index of the Al2O3 lens by changing its thickness and obtain the relationship between effective index and the lens thickness, which can be flexibly utilized in manipulating SPPs. Many previous works on plasmonic lenses focus on the confinement of SPPs, controlling the propagation is significant for integrated plasmonic circuits. We believe that our research will inspire more designs and applications on plasmonic integrated circuits
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