Nano-optical trapping using an all-dielectric optical fiber supporting a TEM-like mode.

Fiber optical tweezers benefit from compact structures and compatibility with fiber optic technology, however, trapping of nano-objects are rarely demonstrated. Here, we present stable optical trapping of a 30-nm polystyrene particle using an all-dielectric coaxial optical fiber supporting an axisymmetric TEM-like mode. We demonstrate, via comprehensive finite-difference time-domain simulations, that the trapping behavior arises from a significant shift of the fiber-end-fire radiation directivity originated from the nanoparticle-induced symmetry breaking, rather than the gradient force which assumes an invariant optical field. Fabrication of the fiber involved is entirely feasible with existing techniques, such as thermal-drawn and electrospinning, and therefore can be mass-produced.