Numerical computation of optical tweezers is one path to understanding the subtleties of their underlying
mechanism—electromagnetic scattering. Electromagnetic scattering models of optical trapping can be used
to find the properties of the optical forces and torques acting on trapped particles. These kinds of calculations
can assist in predicting the outcomes of particular trapping configurations. Experimentally, looking at the parameter
space is time consuming and in most cases unfruitful. Theoretically, the same limitations exist but
are easier to troubleshoot and manage. Towards this end a new more usable optical tweezers toolbox has been
written. Understanding of the underlying theory has been improved, as well as the regimes of applicability of the
methods available to the toolbox. Here we discus the physical principles and carry out numerical comparisons
of performance of the old toolbox with the new one and the reduced (but portable) code.
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.