Resonant binding of dielectric particles to metal surface without plasmonics

TL;DR

This paper demonstrates that dielectric particles can be resonantly bound to metal surfaces through high-Q Mie modes without relying on plasmonics, enabling stable optical trapping with significant forces.

Contribution

It introduces a mechanism for resonant binding of dielectric particles to metal surfaces via Mie resonances, independent of plasmonic effects, and analyzes the resulting optical forces and stable equilibrium positions.

Findings

Resonant optical forces reach nanoNewton scale for micron-sized particles.

Stable binding positions exist where forces balance, enabling trapping.

Mechanical oscillation frequencies around equilibrium are on the order of MHz.

Abstract

High index dielectric spherical particle supports the high-$Q$ resonant Mie modes that results in a regular series of sharp resonances in the radiation pressure. A presence of perfectly conducting metal surface transforms the Mie modes into the extremely high-$Q$ magnetic bonding or electric anti-bonding modes for close approaching of the sphere to the surface. We show that the electromagnetic plane wave with normal incidence results in repulsive or attractive resonant optical forces relative to metal for excitation of the electric bonding or magnetic anti-bonding resonant modes respectively. A magnitude of resonant optical forces reaches order of one nano Newton of magnitude for micron size of silicon particles and power of light $1mW/\mu m^2$ that exceeds the gravitational force by four orders. However what is the most remarkable there are steady positions for the sphere between pulling and pushing forces that gives rise to resonant binding of the sphere by metal surface. A frequency of mechanical oscillations of particle around the equilibrium positions reaches a magnitude of order MHz.