Optical force and torque on small particles induced by polarization singularities.

Area of Science:

• Optics and Photonics
• Nanotechnology
• Light-Matter Interactions

Background:

• Near-field optical forces are crucial for manipulating small particles and molecules on-chip.
• Optical polarization singularities, such as C lines, are key phenomena in near-field optics.

Purpose of the Study:

• To investigate the optical force and torque exerted on small particles by the polarization singularities generated by a gold cylinder.
• To understand the role of electric and magnetic C lines in inducing optical torque and gradient forces.

Main Methods:

• Simulated scattering of light by a gold cylinder to generate electric and magnetic C lines in the near field.
• Analysis of the interaction between these C lines and a dielectric/magnetic particle to determine optical forces and torques.

Main Results:

• The gold cylinder generates both electric and magnetic C lines in its near field.
• These C lines induce complex optical torques on dielectric/magnetic particles due to their intrinsic spin density.
• The near-field evolution of C lines results in gradient forces on the particles, with significant spatial variations.

Conclusions:

• Optical polarization singularities significantly influence light-induced forces and torques on small particles.
• The findings provide new insights into chiral light-matter interactions.
• Potential applications include advanced on-chip optical manipulation and optical sensing technologies.