Optical Forces in Hybrid Plasmonic Waveguides

Abstract

We demonstrate that in a hybrid plasmonic system the optical force exerted on a dielectric waveguide by a metallic substrate is enhanced by more than 1 order of magnitude compared to the force between a photonic waveguide and a dielectric substrate. A nanoscale gap between the dielectric waveguide and the metallic substrate leads to deep subwavelength optical energy confinement with ultralow mode propagation loss and hence results in the enhanced optical forces at low input optical power, as numerically demonstrated by both Maxwell's stress tensor formalism and the coupled mode theory analysis. Moreover, the hybridization between the surface plasmon modes and waveguide modes allows efficient optical trapping of single dielectric nanoparticle with size of only several nanometers in the gap region, manifesting various optomechanical applications such as nanoscale optical tweezers.

Finite-Boundary Bowtie Aperture Antenna for Trapping Nanoparticles

“…According to the work reported in [10,30], the assumption made about the injected power in the calculation is considered low, and safe to the nanoparticles. We infer from the simulation results presented in Figure 4(c) that gold nanoparticles with diameters as small as 12 nm can be stably trapped inside the gap region [29] (since the trapping potential is slightly higher than the kinetic energy of Brownian motion for d = 12 nm). The optical forces exerted on different nanoparticles along the x-direction are also presented in Figure 4(d) which indicates that the nanoparticles will be trapped towards the center of the gap under the action of the forces existing there.…”

“…The optical forces at the top and bottom boundaries are in opposite directions, hence giving rise to steep force gradients and extraordinarily deep potential well. The trapping potentials for different nanoparticles derived from U z = l F · dz [29] are presented in Figure 4(c), which were calculated based on an injected power intensity of 2 mW/µm 2 . These trapping potentials have been normalized to the kinetic energy of the nanoparticles' Brownian motion in water at room temperature (with the trapping potential defined to be zero at some infinitely distant location).…”

Low-Power Far Field Nanonewton Optical Force Trapping Based on Far-Field Nanofocusing Plasmonic Lens

“…Considering this, a theoretical study is carried out here first by means of computational numerical calculations for the purpose of revealing physical picture of far-field trapping behavior by using a circular plasmonic lens. The commercial software "COMSOL Multiphysics 4.3b" is adopted here for the computational calculation and numerical simulation [35][36][37][38][39].…”

Transformation optics beyond the manipulation of light trajectories

“…Optical gradient forces are used in optical tweezers, where microscopic dielectric particles are trapped and moved by laser beams towards regions of highest intensity [76]. In recent years, there is increasing interest to calculate optical forces in complex artificial structures [69,[77][78][79][80][81][82][83][84][85]. Most recently, scientists discussed the use of optical forces to manipulate metamaterials on a microscopic level [78,84,85].…”