The Theory And Capture Characteristics Research Of Near-field Optical Fiber Tweezers

In today’s rapid development of science and technology, researchers are focusing onmicro areas. Especially in the field of biomedical, the operation on the level of singlemolecule is particularly important. Thus in recent years,near-field optical tweezers, with itsown unique advantages, break through the disadvantage of the far-field optical tweezers,which is the limit size of microscope objective and the lack of optical diffraction limit,becomes one of the powerful tools to study the micro area. Therefore, in order to develop amore functional near-field optical tweezers system, this subject is based on the existingmodels of near-field optical tweezers, and combined with inadequacy of existing models tostudy a kind of near-field optical fiber tweezers which based on the twin-core fiber.The system of near-field optical tweezers which based on twin-core fiber can combinethe total internal reflection principle and twin-core optical fiber, and form a evanescent fieldon the end face of fiber to achieve the capture of objects, Using twin-core fiber to constitutenear-field tweezers, superposition of opposite coherent optical transmission constitutes thecapture area, interference effect makes the light intensity increased, makes the capture spacereduced, and this system can separate the near-field optical tweezers with its manipulation andmicroscopic observation system. Meanwhile, the near-field optical tweezers processingmethod is simple and repeatable.The near-field optical tweezers based on twin-core fiber, first we grind a twin-core fiberwith a certain angle into a conical structure, and then we coat the surface of fiber cone withhighly reflective metal film. For this near-field optical fiber tweezers system constituted bythis structure, we use a two-dimensional finite-difference time-domain method for lightfield of fiber end out for a simulation analysis, and we calculate the light trapping force of themicron-sized particles by finite element method. Different shapes of fiber end face of adifferent incident angle was discussed, when there is a phase difference between two beams oflight the distribution of the light field. We also calculated the optical trapping force ofdifferent sizes of particles at the same position in the field of vertical distribution. Same sizeparticles at different distances from the fiber end surface of horizontal distribution of opticaltrapping force and same size particles under different conditions of incidence angle of horizontal distribution of optical trapping force. In theory, fully demonstrate the stability ofthe model to capture characteristics by the simulation and calculation.