Computational modelling of optical tweezers with many degrees of freedom using dynamic simulation: cylinders, nanowires, and multiple particles

Yongyin Cao; Alexander B. Stilgoe; Martin Stroet; Vincent L. Y. Loke; Lixue Chen; Timo A. Nieminen; Halina Rubinsztein-Dunlop

doi:10.1117/12.930137

10 October 2012 Computational modelling of optical tweezers with many degrees of freedom using dynamic simulation: cylinders, nanowires, and multiple particles

Yongyin Cao, Alexander B. Stilgoe, Martin Stroet, Vincent L. Y. Loke, Lixue Chen, Timo A. Nieminen, Halina Rubinsztein-Dunlop

Author Affiliations +

Proceedings Volume 8458, Optical Trapping and Optical Micromanipulation IX; 84582V (2012) https://doi.org/10.1117/12.930137
Event: SPIE NanoScience + Engineering, 2012, San Diego, California, United States

Abstract

Computational tasks such as the calculation and characterization of the optical force acting on a sphere are relatively straightforward in a Gaussian beam trap. Resulting properties of the trap such as the trap strength, spring constants, and equilibrium position can be easily determined. More complex systems with non-spherical particles or multiple particles add many more degrees of freedom to the problem. Extension of the simple methods used for single spherical particles could result in required computational time of months or years. Thus, alternative methods must be used. One powerful tool is to use dynamic simulation: model the dynamics and motion of a particle or particles within the trap. We demonstrate the use of dynamic simulation for non-spherical particles and multi-particle systems. Using a hybrid discrete dipole approximation (DDA) and T-matrix method, we find plausible equilibrium positions and orientations of cylinders of varying size and aspect ratio. Orientation landscapes revealing different regimes of behaviour for micro-cylinders and nanowires with different refractive indices trapped with beams of differing polarization are also presented. This investigation provides a solid background in both the function and properties of micro-cylinders and nanowires trapped in optical tweezers. This method can also be applied to particles with other shapes. We also investigate multiple-particle trapping, which is quite different from single particle systems, as they can include effects such as optical binding. We show that equilibrium positions, and the strength of interactions between particles can be found in systems of two and more particles.

Citation Download Citation

Yongyin Cao, Alexander B. Stilgoe, Martin Stroet, Vincent L. Y. Loke, Lixue Chen, Timo A. Nieminen, and Halina Rubinsztein-Dunlop "Computational modelling of optical tweezers with many degrees of freedom using dynamic simulation: cylinders, nanowires, and multiple particles", Proc. SPIE 8458, Optical Trapping and Optical Micromanipulation IX, 84582V (10 October 2012); https://doi.org/10.1117/12.930137

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