Subwavelength-scale off-axis optical nanomanipulation within Gaussian-beam traps

Area of Science:

• Optics
• Nanotechnology
• Physics

Background:

• Traditional optical traps with focused Gaussian beams typically exhibit a single optical potential-well near the focal point.
• The role of scattering force in optical trapping has often been associated with reduced trapping stability.

Purpose of the Study:

• To demonstrate the existence of additional optical potential-wells in Gaussian-beam optical traps.
• To explore the potential for optical manipulation at the subwavelength scale in off-focus planes.
• To investigate the combined effects of gradient and scattering forces on trapping phenomena.

Main Methods:

• Theoretical analysis of optical forces (gradient and scattering) acting on particles within a focused Gaussian beam.
• Numerical simulations to model the optical potential-wells and force fields.
• Parametric studies involving particle size, material (metallic and dielectric), and transverse plane position.

Main Results:

• Identification of novel, off-focus optical potential-wells in Gaussian-beam optical traps.
• Demonstration that these wells arise from the synergistic interaction of gradient trapping force and transverse scattering force.
• Validation of trapping capabilities for both metallic and high refractive-index dielectric nanoparticles.
• Tailorable force fields and potential-wells for manipulating nanoparticles at subwavelength scales and varying off-axis distances.

Conclusions:

• Gaussian-beam optical traps possess previously unrecognized potential-wells for subwavelength manipulation.
• The synergy between gradient and scattering forces is crucial for forming these novel trapping sites.
• Engineered optical forces enable precise control over nanoparticle manipulation, opening avenues for advanced applications.