3-dimensional plasmonic nanomotors enabled by independent integration of Optical Pulling and Lateral Forces

TL;DR

This paper introduces a novel 3D nanomotor design that independently controls pulling, pushing, and lateral motion using optical forces, enabling advanced manipulation of nanoscale objects with light.

Contribution

It presents a new nanomotor design that combines optical pulling and lateral forces through innovative use of Bessel beams and plasmonic dimers, allowing independent 3D motion control.

Findings

Achieves realistic optical pulling forces with azimuthally polarized Bessel beams.

Demonstrates lateral motion control via asymmetric plasmonic dimers.

Shows suppression of unwanted displacements and rotations over time.

Abstract

Light-matter interactions generally involve momentum exchange between incident photons and the target object giving rise to optical forces and torques. While typically weak, they become significant at the nanoscale, driving intense research interest in the exploitation of photon recoil to drive micro- and nanostructures. While great progress has been attained in controlling transversal degrees of freedom, three-dimensional movement remains challenging, particularly due to the impractical realization of pulling forces that oppose the direction of incident light. Here we theoretically present a novel nanomotor design that enables independent control over both transverse and longitudinal motion. This design exploits coupling between an azimuthally polarized Bessel beam and a dielectric glass cylinder to realistically achieve optical pulling forces. At the same time, asymmetric plasmonic dimers, embedded within the cylinder, provide lateral motion, through asymmetric scattering under plane wave illumination. We further demonstrate that unwanted displacements and rotations can be restrained, even at long illumination times. Our design unlocks a new degree of freedom in motion control, allowing for pulling, pushing, and lateral movement by simply tuning the polarization or switching between plane waves and Bessel beams.