Driven optical matter: Dynamics of electrodynamically coupled nanoparticles in an optical ring vortex.

Area of Science:

• Colloidal science
• Nanophotonics
• Soft matter physics

Background:

• Investigated driven colloidal systems, focusing on hydrodynamic interactions.
• Neglected electrodynamic interactions from optical fields in previous studies.

Purpose of the Study:

• Investigate interparticle dynamics in driven colloidal systems, considering electrodynamic interactions.
• Analyze nanoparticle behavior in an optical ring vortex trap with silver nanoparticles.
• Evaluate the impact of gold nanoplate mirrors on optical trapping and nanoparticle manipulation.

Main Methods:

• Utilized optical ring vortex traps with 150-nm silver nanoparticles.
• Employed gold nanoplate mirrors in a retroreflection geometry for enhanced trapping.
• Conducted experiments and electrodynamics-Langevin dynamics simulations.
• Performed comparative measurements with driven polystyrene beads.

Main Results:

• Demonstrated that electrodynamic interactions are significant in optically driven colloidal systems.
• Showcased enhanced optical trapping and reduced hydrodynamic friction using gold nanoplate mirrors.
• Revealed position-dependent optical drive forces and interparticle interactions for linearly polarized light.
• Observed increased fluctuations in interparticle separation with increasing optical driving force.

Conclusions:

• Electrodynamic forces and interactions are crucial in optically driven colloidal systems and should not be neglected.
• Gold nanoplate mirrors create superior optical traps, increasing field intensity and drive force.
• Nonuniform optical drive forces lead to position-dependent nanoparticle velocities and increased fluctuations.
• The findings resolve open issues regarding periodic modulation of interparticle separation in driven colloidal systems.