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Wednesday, March 27, 2019

Optical forces and torques exerted on coupled silica nanospheres: novel contributions due to multiple scattering

R M Abraham Ekeroth

When illuminated by light, optically coupled nanoparticles suffer the action of multiple electromagnetic forces. In general, two kinds of forces are assumed: binding forces that make the particles attract/repel each other and scattering forces that push the system forwards. Tangential forces and orbital torques can also be induced to align the interacting particles with the electric field. In this work, new degrees of freedom were found for two coupled silica nanospheres under illumination with linearly-polarized plane waves. The results have a general validity for arbitrary mesoscale systems: multiple scattering of light induces unusual torques and deviation forces. These torques include spin contributions to the movement of the whole system. The results are supported by previous works and pave the way for the engineering of nanoscale devices and nanorotators. Any application based on photonics at mesoscales should take into account the new movements predicted here.

DOI

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