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Register a new userOff-axis dipole forces in optical tweezers by an optical analog of the {Magnus} effect
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Added by
Robert J. C. Spreeuw
Publication date
2020
fields
Physics
and research's language is
English
Authors
Robert J. C. Spreeuw
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It is shown that a circular dipole can deflect the focused laser beam that induces it, and will experience a corresponding transverse force. Quantitative expressions are derived for Gaussian and angular tophat beams, while the effects vanish in the plane-wave limit. The phenomena are analogous to the Magnus effect pushing a spinning ball onto a curved trajectory. The optical case originates in the coupling of spin and orbital angular momentum of the dipole and the light. In optical tweezers the force causes off-axis displacement of the trapping position of an atom by a spin-dependent amount up to $lambda/2pi$, set by the direction of a magnetic field. This suggests direct methods to demonstrate and explore these effects, for instance to induce spin-dependent motion.
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