Optical Manipulation Of Biological Partiles Using LP₂₁ Mode In Fiber

Biology takes an important role in the human history, especially when laser and optical tweezer become the most powerful tool in all over the fields. The optical tweezer is the best choice in the fields of biology, physical chemistry and soft condensed matter physics.Recent study promises that the optical tweezers go out of the laboratory and into the mainstream to be a consumer product.We demonstrate the optical manipulation of biological particles using a low-order LP21 fiber mode. The focused four-lobed LP21 mode distribution with twisting and bending characteristics was theoretically and experimentally found to be effective in optical tweezers applications, including selective cellular pick-up, pairing, grouping or separation, as well as rotation of cell dimers and clusters. By using ray-optics model, our proposed theoretical model estimates both the translational dragging force and rotational torque in good accordance with experimental data. With a simple all-fiber configuration, and low peak irradiation to target bioparticles, the proposed LP21 "optical chuck" system has great application potential in biological test systems.Firstly, the development and principle of optical tweezer are introduced, especially single fiber optical tweezers. Optical trap in three dimensions results from scattering force and gradient force, which are analyzed in detail.Secondly, derivation of ray-optics model based on geometry optics principle with Mie spherical particle, quantitative calculation and numerical simulation of the force in LP21 mode are shown.Thirdly, the theories and characteristics are described, including the fiber coupled mode theory, the twist and bend characteristic of fiber LP21 mode.Fourthly, We demonstrate the optical manipulation of biological particles using a low-order LP21 fiber mode. The single fiber optical tweezers is effective in trapping particles, as well as rotation of cell dimers.Lastly, we give the conclusion of this paper and prospect the future research of fiber optical tweezers and LP21 mode.