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Optical trapping of dielectric particles in arbitrary fields
1European Molecular Biology Laboratory, Heidelberg, Germany. alexander.rohrbach@EMBL-Heidelberg.de
Summary
We developed a new method to calculate optical trapping forces for small dielectric particles in electromagnetic fields. This approach accurately determines gradient and scattering forces, validated by comparison with existing methods.
Area of Science:
- Physics
- Optics
- Nanotechnology
Background:
- Optical trapping utilizes light forces to manipulate microscopic particles.
- Calculating forces on dielectric particles in complex electromagnetic fields is challenging.
- Existing methods may lack accuracy for particles comparable to the wavelength of light.
Purpose of the Study:
- To introduce a novel method for calculating optical trapping forces.
- To accurately determine both gradient and scattering force components.
- To investigate particle trapping in focused electromagnetic fields with specific conditions.
Main Methods:
- Representing incident fields and particles using plane-wave spectra.
- Calculating scattering forces via momentum transfer in single- and double-scattering.
- Employing the second-order Born series solved in the frequency domain using Ewald constructions.
Main Results:
- The new method accurately calculates trapping forces for dielectric particles (D ≤ λ).
- Numerical results show satisfying agreement with established calculation methods.
- The approach is applied to analyze axial trapping under focused waves, considering aperture effects and refractive index mismatch.
Conclusions:
- The presented method provides a reliable way to compute optical trapping forces.
- It offers accurate analysis for particles in arbitrary electromagnetic fields.
- The findings are relevant for applications in optical manipulation and nanotechnology.