Impact of a laser magnetic field on optical trapping

Optical tweezers have proved to be indispensable tools for micro-manipulation. However, the application of large forces using optical tweezers requires high laser intensity, which could be destructive in the case of biological samples. By embedding magnetite nanoparticles in a polystyrene matrix, we get a trap stiffness similar to 15 times higher than that of similar plain beads as a result of the response to both the electric and magnetic fields of the laser beam. Our approach allows for measurement of the magnetic properties of materials in the range of the laser frequency. Our theoretical calculations predict that incorporating the effective complex permeability and permittivity for a microbead could generate significantly large optical forces, up to micro-Newtons. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement