Multi-Stability in Dual-Fiber Optical Trap

The special feature of multi-stability of a dual-fiber optical trap in the axial direction is demonstrated in this work. Two identical counter-propagating laser beams are used to trap a microsphere both axially and transversely. Based on the theoretical calculation and numerical results, it´s found that the balance point for trapping in the axial direction can be in the centre middle as reported in former studies, or there could be two balance points each located between the center and fiber end, and three stable points shows up together as the simulation parameters of the trap change in one way or another. The stability in the axial direction shows indeterminacy and multiple situations exist.