Optical fiber probe with a concave cavity for non-contact trapping

We demonstrate a non-contact trapping of a yeast cell by an optical fiber probe with a micron-size concave cavity both theoretically and experimentally. We fabricate the optical fiber tip with a micron-size concave cavity by the improved tube etching method. The size of the concave cavity can be controlled by the etching parameters, such as the etching time, the etching solution, and so on. The output fields from the fiber tips with concave cavities of two geometrical sizes (microns and tens of microns) are computed and analyzed. Then the optical forces on a yeast cell by these concave fiber tips (CFTs) are calculated and discussed. The theoretical results predicate that a micron-size CFT can be used for non-contact trapping of a yeast cell. We observe the non-contact trapping of a yeast cell by a micron-size CFT in the experiments and measure the trapping forces. The optical trapping and manipulation based on these micron-size CFTs may provide versatile applications in bio-science and medical research.