Abstract
In this paper we show analytically and numerically the formation of a near-field stable optical binding between two identical plasmonic particles, induced by an incident plane wave. The equilibrium binding distance is controlled by the angle between the polarization plane of the incoming field and the dimer axis, for which we have calculated an explicit formula. We have found that the condition to achieve stable binding depends on the particle’s dielectric function and happens near the frequency of the dipole plasmonic resonance. The binding stiffness of this stable attaching interaction is four orders of magnitude larger than the usual far-field optical binding and is formed orthogonal to the propagation direction of the incident beam (transverse binding). The binding distance can be further manipulated considering the magneto-optical effect and an equation relating the desired equilibrium distance with the required external magnetic field is obtained. Finally, the effect induced by the proposed binding method is tested using molecular dynamics simulations. Our study paves the way to achieve complete control of near-field binding forces between plasmonic nanoparticles.
Highlights
In this paper we show analytically and numerically the formation of a near-field stable optical binding between two identical plasmonic particles, induced by an incident plane wave
We demonstrate that two plasmonic nanoparticles can form a stable bound dimer even when the separation distance is significantly shorter than the wavelength and as small as three times the radius of the particles
The effect of the near-field binding forces is much larger than the mid-far field forces resulting in enhancement of 4 orders of magnitude of the trap stiffness compared to the common stable optical binding configuration
Summary
We are going to analyze in detail the equilibrium points located in the near field region, which are given by These fields are obtained self-consistently by solving the scattering problem given by Eq (2), that includes the full interaction between the dipoles. Which gives the required angle of polarization of the incident plane wave for a given equilibrium distance d Notice that in this configuration, Fy = 0 and azimuthal force arises. In order to gain a clearer physical insight about the previous results, we consider briefly the near field approximation In this approach, the components of the Green dyadic tensor are given by: Gxx|NF ∼ 4π k2d3 −1.
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