Tunable optical pulling force mediated by resonant electromagnetic coupling

Area of Science:

• Optics
• Nanotechnology
• Materials Science

Background:

• Optical manipulation typically relies on scattering forces, leading to pushing effects.
• Optical pulling force (OPF) is a counterintuitive phenomenon defying classical expectations based on momentum conservation.
• Controlling OPF is crucial for advanced applications in nanotechnology and materials science.

Purpose of the Study:

• To investigate the tunable optical pulling force (OPF) on low refractive index nanoparticles (NPs) within a hybrid dimer system.
• To elucidate the physical mechanism behind OPF, focusing on near-field electromagnetic coupling.
• To explore the influence of geometrical parameters and illumination conditions (plane wave, Gaussian beam) on OPF.

Main Methods:

• Analytical investigation using the coupled dipole approximation method.
• Numerical simulations employing the finite-difference time-domain (FDTD) method.
• Evaluation of OPF dependence on system geometry and beam characteristics.

Main Results:

• Tunable OPF is demonstrated on low refractive index NPs in a hybrid plasmonic-dielectric dimer system.
• Near-field electromagnetic coupling between dielectric and plasmonic NPs is identified as the key mechanism.
• Pure OPF, free from transverse forces, is achieved using a Gaussian beam illumination.

Conclusions:

• The study provides a comprehensive understanding of tunable OPF in hybrid nanostructures.
• Near-field coupling offers a novel pathway for generating and controlling optical forces.
• The proposed method enhances optical manipulation capabilities for sorting, transport, and trapping of nanoparticles.