Binding of Resonant Dielectric Particles to Metal Surfaces Using Plasmons

Abstract

Forces between dielectric particles induced by optical fields can bind them into new systems, varying from optical molecules to large aggregates. Here it is shown that surface plasmons can bind resonant dielectric particles to the waveguiding surfaces resulting in stable levitation of the particles by the optical forces alone. At the same time, the particles can be propelled efficiently along the surface. The predictions follow from solving the 3D electromagnetic problem of plasmon scattering on a dielectric microsphere near the metal surface. To tackle the problem, an accurate and fast hybrid approach is developed: the fields are expanded into 2D angular components which are calculated using finite‐difference time‐domain simulations. The rigorous numerical results are also explained qualitatively using an analytically solvable model in which a resonant magnetic dipole illuminated by a plasmon interacts with the surface. The particle binding to surfaces is a remarkable outcome of the strong optical interaction at nanoscale and it may offer new configurations for particle manipulations by guided waves, especially in chip‐scale structures.

Resonant binding of dielectric particles to metal surface without plasmonics

“…Obviously, a presence of surface which reflects incident plane wave can drastically change a situation with the equilibrium positions for particles, i.e., the surface can trap particles outside. Dielectric surface can trap particles using the evanescent tails of waveguide modes [6] while metal surface can trap particles due to excitation of surface plasmonic waves by oblique plane waves [7][8][9][10][11][12][13]. A key issue in particle trapping by evanescent tails is the formation of a stable equilibrium in the transverse direction which is rather close to the surface while in the direction along the surface the stability of particles is remaining in question.…”