Research On Single Fiber Optical Tweezers

Single fiber optical tweezers which is a new kind of fiber optical tweezers are systematically analyzed in this dissertation. Compared with traditional optical tweezers single fiber optical tweezers is more suitable for practical use with its handling flexibility and low cost. The possibility of forming a single fiber optical tweezers is discussed. The computation of the optical trapping force is achieved by using a FDTD (Finite-Difference-Time-Domain) method. Combining FDTD method with electromagnetic field momentum conservation law, the calculation of optical fiber light field distribution and the calculation of optical trapping force are related. This technique has been used to calculate the light field distribution from different types of fiber probes and optical forces exerted on different particles. Based on these numerical results, the relation between the output laser beam's spot size and the fiber probe's taper angle is given and the dependence of the 3-D optical trap on the output laser beam is also discussed. The conclusion on the conditions for forming single fiber optical tweezers is finally presented.The fabrication method of fiber probe used in the single fiber optical tweezers is expatiated, and the single fiber optical tweezers system is set up. Based on the system, many kinds of fiber optical tweezers could be easily constructed, three types of single fiber optical tweezers are introduced. By using these systems the 3-D trapping and manipulation of yeast cells in water is easily achieved. Furthermore with two of such systems the transportation of the cells from one tweezers to the other tweezers is achieved and the cell's spatial state can be adjusted too. The Brownian motion of the trapped yeast cell in water is observed and the Brownian motion force is measured. Based on the experimental results the maximum optical trapping forces of different types of single fiber optical tweezers versus the input optical power is illustrated. This work has great significant for the research and development of the single fiber optical tweezers. It is of importance reference value to optical tweezers research in instrument design and its wider application in life science and biography technology.