Microparticle movements in optical funnels and pods.

Area of Science:

• Optics and Photonics
• Microparticle Manipulation
• Laser Physics

Background:

• Optical trapping utilizes focused laser beams to manipulate microscopic particles.
• Laguerre-Gaussian (LG) modes are crucial for imparting orbital angular momentum (OAM) to light.
• Controlling 3D particle trajectories and rotation is essential for advanced applications.

Purpose of the Study:

• To experimentally investigate 3D microparticle movement induced by novel funnel- and tubular pod-like laser beams.
• To explore the influence of beam structure and orbital angular momentum density on particle trajectories.
• To assess the potential of these beams for volumetric optical particle manipulation.

Main Methods:

• Synthesis of funnel and pod beams via coherent superposition of helical LG modes using computer-generated holograms and a spatial light modulator.
• Precise 3D particle tracking using the in-line holography method.
• Experimental observation of microparticle behavior within the optical trap.

Main Results:

• Demonstrated that trapped microparticles follow distinct trajectories determined by the beam's OAM density.
• Observed that particles exhibit opposite rotation directions when manipulated with the proposed pod beam.
• Successfully controlled 3D microparticle motion using single-beam optical traps.

Conclusions:

• The study highlights the capability of tailored laser beam structures to precisely control microparticle dynamics in three dimensions.
• The observed control over particle trajectory and rotation direction opens avenues for advanced optical manipulation.
• The developed single-beam traps show promise for applications in volumetric particle assembly and manipulation.