Optical binding via surface plasmon polariton interference

TL;DR

This paper demonstrates how surface plasmon polariton waves enable stable, subwavelength optical binding of nanoparticles near metal surfaces, surpassing classical diffraction limits and allowing anisotropic particle arrangements.

Contribution

It reveals the role of surface plasmon polaritons in mediating optical binding, enabling subwavelength stable dimers and anisotropic configurations not possible in free space.

Findings

Resonant surface waves enable subwavelength stable dimers.

Surface modes allow binding along dipole moments, unlike vacuum binding.

Optical binding stiffness is enhanced tenfold by surface plasmon polaritons.

Abstract

Optical binding allows creation of mechanically stable nanoparticle configurations owing to formation of self-consistent optical trapping potentials. While the classical diffraction limit prevents achieving deeply subwavelength arrangements, auxiliary nanostructures enable tailoring optical forces via additional interaction channels. Here, a dimer configuration next to metal surface was analyzed in details and the contribution of surface plasmon polariton waves was found to govern the interaction dynamics. It was shown that the interaction channel, mediated by resonant surface waves, enables achieving subwavelength stable dimers. Furthermore, the vectorial structure of surface modes allows binding between two dipole nanoparticles along the direction of their dipole moments, contrary to vacuum binding, where a stable configuration is formed in the direction oriented perpendicularly to the polarization of dipole moments. In addition, the enhancement of optical binding stiffness for one order of magnitude was predicted owing to the surface plasmon polariton interaction channel. These phenomena pave a way for developing new flexible optical manipulators, allowing for the control over a nanoparticle trajectory on subwavelength scales and opens a room of opportunities for optical-induced anisotropic, i.e. with different periods along the field polarization as well as perpendicular to it, organization of particles on a plasmonic substrate.