Zheng-Xun Xiang, Xiang-Shi Kong, Xu-Bo Hu, Hai-Tao Xu, Yong-Bing Long, and Hai-Dong Deng
The effects of resonant mode interference on optical forces acting on gold core-silicon shell nanoparticles are theoretically investigated with the multipolar expansion method based on the Mie scattering theory. It is found that the total optical radiation force and its two components, the incident force and the recoil force, can be tuned flexibly by engineering the interference interaction among electric, magnetic, and anapole modes. The recoil force acting on the core-shell nanoparticles can be enhanced up to 17 pN compared with the pure silicon nanoparticles with the same size as that of the core-shell nanoparticles when the magnetic dipole resonant mode totally interferes with the electric dipole resonant mode. In addition, the incident force can also be improved to 25 pN by suppressing the interference between the electric dipole and the magnetic dipole resonances. More importantly, the maximum optical radiation force is not dominated by the strongest resonant scattering mode of the hybrid nanostructure due to the modes’ interference induced giant negative recoil forces. We hope our results not only improve the optical trapping and manipulation of core-shell nanoparticles but also help to understand the underlying physical mechanism regarding the tunable optical radiation forces induced by the tunable interference among different resonant modes in core-shell nanoparticles.
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