Lateral forces on particles induced by magnetic spin-orbit coupling

Optical forces in optical tweezers enable non-contact, non-destructive trapping and manipulation of particles. One such force has been found to originate from the spin-orbit coupling of light, which produces a counter-intuitive lateral optical force on metal nanoparticles due to the spin of the electric-field components of light. Here we reveal that the spin-orbit coupling of the magnetic-field components of light also produces a lateral optical force on particles. To study this lateral force, we designed a gapped structure composed of a dielectric particle near photonic crystal surface, and found that the lateral force originates from the spin-dependent excitation of a Bloch surface wave. We further demonstrate that the lateral force can be modified by tuning the structural parameters of the gapped structure and by exploiting the magnetic resonance modes of the particle. This work should contribute to a deeper understanding of the magnetic spin-orbit coupling between light and matter and promote the development of particle manipulation on dielectric platforms. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement