Generalized Lorentz Mie Theory of Reversal of Optical Trapping Force

Recently, the role of ultrafast pulsed excitation in laser trapping of dielectric nanoparticles has been explored [1-4] and it was observed that optical Kerr effect (OKE) plays an important role in determining the stability of the trap [2-4]. Using Generalized Lorentz Mie Theory (localized approximation) [5], here we theoretically investigate how optical trapping force/potential on a hollow-core polystyrene nanoparticle becomes repulsive to attractive in nature under high repetition-rate femtosecond pulsed excitation.