Characterization of trapping force on metallic mie particles

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Optical trapping utilizes focused laser beams to manipulate microscopic particles.
• Metallic nanoparticles exhibit unique optical properties due to surface plasmon resonance.
• Understanding forces on metallic particles is crucial for applications in plasmonics and nanophotonics.

Purpose of the Study:

• To measure and analyze the transverse trapping force on metallic Mie particles (gold, nickel, silver).
• To investigate the influence of numerical aperture (NA) on trapping efficiency.
• To compare experimental findings with a modified ray-optics model, considering radiometric and spherical aberration forces.

Main Methods:

• Experimental measurement of transverse trapping force on gold, nickel, and silver particles.
• Utilizing an objective lens with varying numerical apertures for optical trapping.
• Theoretical calculations using a modified ray-optics model.

Main Results:

• Transverse trapping efficiency of metallic particles increases with the numerical aperture of the trapping objective.
• Radiometric force, arising from laser-induced heating, is a significant factor.
• The modified ray-optics model accurately predicts experimental results when considering radiometric force and spherical aberration.

Conclusions:

• The numerical aperture plays a critical role in enhancing the transverse trapping efficiency of metallic particles.
• Radiometric force is a dominant effect in optical trapping of metallic particles, approximately ten times stronger than the transverse trapping force.
• The study validates a modified ray-optics model for predicting optical forces on metallic nanoparticles, crucial for advanced nanophotonic applications.