ABSTRACT
The forces and torques exerted on a particle within optical tweezers arise from the change in the trapping beam’s momentum as it is transmitted through, or scattered by, the particle. However, although the underlying physical principles may be simple, the implementation of a precise quantitative model is not. In essence, the complexity arises because the trapped particles are of a size comparable to the optical wavelength. Hence, the particles are too large to be treated as point objects in a spatially varying eld and too small to simply model the transmission of the light in terms of ray optics.
