Exploiting extraordinary topological optical forces at bound states in the continuum

Polarization singularities and topological vortices in photonic crystal slabs centered at bound states in the continuum (BICs) can be attributed to zero amplitude of polarization vectors. We show that such topological features are also observed in optical forces within the vicinity of BIC, around which the force vectors wind in the momentum space. The topological force carries force topological charge and can be used for trapping and repelling nanoparticles. By tailoring asymmetry of the photonic crystal slab, topological force will contain spinning behavior and shifted force zeros, which can lead to three-dimensional asymmetric trapping. Several off-Gamma BICs generate multiple force zeros with various force distribution patterns. Our findings introduce the concepts of topology to optical force around BICs and create opportunities to realize optical force vortices and enhanced reversible forces for manipulating nanoparticles and fluid flow.

Automated summary

Polarization singularities and topological vortices are observed in photonic crystal slabs centered at bound states in the continuum (BICs), which can be attributed to zero amplitude of polarization vectors. Optical forces around BICs exhibit similar topological features, with force vectors winding in the momentum space. These topological forces can be used to trap and repel nanoparticles, providing opportunities for manipulating nanoparticles and fluid flow.