Size selective trapping with optical "cogwheel" tweezers.

Area of Science:

• Optics
• Biophysics
• Microscopy

Background:

• Optical tweezers utilize light beams to manipulate microscopic objects.
• Laguerre-Gaussian beams, or "doughnut-beams," possess unique intensity profiles.
• Controlling particle size selection in optical manipulation is crucial for various applications.

Purpose of the Study:

• To investigate the size-selective trapping capabilities of Laguerre-Gaussian beams and "cogwheel"-shaped beams.
• To explore the application of these light modes in constructing passive particle sorters for microscopy.

Main Methods:

• Experimentally generated Laguerre-Gaussian and "cogwheel"-shaped beams using a spatial light modulator (SLM).
• Utilized an optical tweezers setup integrated with a microscope.
• Investigated the trapping behavior of particles with varying sizes relative to the beam's ring diameter.

Main Results:

• Demonstrated that Laguerre-Gaussian and "cogwheel"-shaped beams can trap particles selectively based on size.
• Observed that particles are trapped when their size exceeds the beam's ring diameter by a specific amount.
• The "cogwheel"-shaped beam, a superposition of two doughnut beams, exhibits modulated light intensity around a spherical volume.

Conclusions:

• Laguerre-Gaussian and "cogwheel"-shaped beams offer a promising method for size-selective particle trapping.
• These light modes can be integrated into microscopy systems to create passive optical sorters.
• This technique provides a convenient approach for sorting particles of different sizes in microscale applications.